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  #21  
Old August 18th, 2005, 09:29 PM
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James Falchetto
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Jason,
I think it's a gauge problem if you took care of the fan cluthc by removing the mechanical fans and putting electric and doing the head gasket. I had the same issue on 3 of my cars (I run 7 one a daily basis for work here in the UAE and trust me TEMPERATURe is an issue in a place where the mercury rises over 120F on a regular basis in the summer). I read somewhere on this website that VDO recommended not putting white tape on the threads in order to ensure a better seal between intake and ground from probe.
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  #22  
Old August 23rd, 2005, 12:11 AM
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Before you go nutty changing head gaskets or any of the like....the fact that your car overheats at idle in traffic is the opposite of the problem most people encounter. I have had three D-90s, and two overheated. The 1995 I have now overheated when it was doing lots of work, like towing a trailer with my 700 lb Harley on it...going up hill with the a/c on. Bad radiator. Problem fixed. But my old truck, a 1994, overheated in traffic at idle like yours. We replaced the radiator with a re-core. It still overheated. Changed out the water pump, sensor, gauge, and viscous fan. It still overheated. Got another re-core from the same guy, problem SOLVED. We looked in the original recore and it had one whole core FULL OF SOLDER!! Just because you have changed a part don't mean it is good.

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  #23  
Old August 23rd, 2005, 01:05 AM
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overheat

I had the same problem, just had the radiator recore, problem is gone so far.
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  #24  
Old September 6th, 2005, 04:45 PM
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OK, so the problem persists! I've done everything I can think of except head gasket and re-replace components I've already replaced.

SO:
1) new thermostat
2) new 4-core monster radiator
3) new water pump
4) new dual electric fans
5) new gauge temp sending unit

Now, for the first time, after a long Labor Day weekend drive and subsequent overheating in stop-go traffic (necessitating turning off truck, blasting heater -- sweating arse off -- and leaving electric fans running to keep temp below red zone -- REPEATEDLY) I noticed coolant leaking from the head - near the front on the driver's side there is a little trail down the side of the block from the head-block joining area (eg head gasket) and a green drop hanging onto the oil pan.

The strange thing is that the cooling system was tested at a shop and held pressure.. and there is no apparent coolant in the oil or oil in the radiator or any type of funny smoke in the exhaust. Certainly the head gasket needs changing now..... so I'll bit the $$bullet and have it done. The only other problem could be a bad re-cored radiator or other new-bad component... or a clog in the cooling system somewhere.

I hate to put money into this 3.9 when I want to dump it eventually.

The symptoms are the same: when idling and not moving the thing gets hotter and hotter and the needle pushes towards the red. I have to shut down the engine prior to this & let the fans cool it off before restarting. Doing this sometimes causes problems - the starter refuses to work sometimes after getting too hot. Nothing like overheating and then stuck with a non-functioning starter....once it cools off for awhile, it seems to fire up. I noticed that the heat shield on the solenoid was a bit tweaked so I adjusted it a bit.

As long as I'm moving moderatly (15mph+) there are no heating problems. I wonder - because there are no hood louvers, could the heat be just trapped under the hood, making the situation worse at idle or when creeping along?

Also, I had someone else do the water pump -- could the housing be corroded and thus there be too much clearance between the impeller and the housing? I didn't ask the mechanic to check that.

Anyway, if it still overheats with a new head gasket I am taking it out into the field and shooting it (and putting in a new engine I think). Perhaps I'm wasting money, but I don't have the time right now to setup a new motor as I'd like to, and this thing only overheats in very heavy stop-go traffic (usually nothing I run into commuting to work) so it only doesn't work when I need it for fun things....
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  #25  
Old September 6th, 2005, 05:09 PM
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I have had the same problem. What I did is went with a mechanical guage/sender and i get an actual temp reading from the engine.
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  #26  
Old September 6th, 2005, 05:10 PM
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I had the same symptoms you describe. A head gasket job fixed it. Only took me a week or so in my garage in the evenings and on the weekend.
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  #27  
Old September 26th, 2005, 09:20 PM
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Nearly ready to take this truck out into the field and shoot it. Maybe the holes would allow better ventilation and thus cooling??

The head gasket is now replaced, and it STILL overheats!! The gasket was absolutely bad - I could see coolant trickling down the side of the block when hot. That doesn't happen anymore, but it still overheats when sitting still.

Here is the history of the problems and attempted solutions, including what was replaced, in order:

1) First time driving the truck for any extended period of time I ended up in city traffic and it overheated. Upon inspection, the clutch fan was very obviously bad. The symtom was creeping up temp gauge and eventual idiot light illumination (that only happened once!) when stopped or just creeping in traffic. This occurred at night when it was not particularly hot outside.

Replaced clutch fan with dual electric fans.

2) dual electric fans seemed to help alot - now under normal driving I never had a problem (eg driving where you are in motion most of the time). In the end, it turns out that it really just delayed overheating; now the truck could last much longer in stopped conditions. The next time I noticed the problem was while on an offroading trip - out in the desert, in some heat, prolonged creeping, the temp gauge started a rapid rise, requiring truck shutdown and cool-off period. While offroading at night, the problem did not arise - so, I assumed that the ambient temperature had something to do with it.

Since I planned to install AC and wanted more cooling capacity anyway, I decided I might as well get a custom 4-core radiator. I also changed thermostat, radiator cap and checked hoses/lines carefully.

3) this seemed to make little to no difference. The truck still overheated in prolonged traffic stops. Coming over the border from Mexico in the summer sun at Mexicali after a little offroading was an overheating nightmare.

Changed water pump, pressure tested cooling system (OK, holding pressure).

4) this had no noticeable effect, either. After some playing around I found that ambient temperature did not seem to make a difference - sitting still for any lenght of time, despite outside temp, would result in an overheating truck - accoring to the gauge, anyway.

Changed temp sending unit.

5) no change in gauge behavior, but I did notice for the first time a leaking head gasket -- a small trickle down the side of the block. Ah-ah! Well, this was the most expensive exploratory surgery to do, so until this point I'd never seen proof the head gasket was bad.

Bit the bullet and changed head gasket. Both heads - tanked, decked and valve job performed. No leaks!

6) STILL OVERHEATING!! I have now spent some $2K on this problem, which could have better spent on my way to a 2.8L PS diesel! I have come to the conclusion that the blown head gasket could have been a result of the overheating, not the cause.

WTH to do now?

The only things not replaced which involve cooling:

1) wires to/from temp gauge
2) temp gauge
3) heater core and hoses
4) intake manifold and block

So, either I have a bad replacement component which results in the exact SAME symptom as before, or I've not yet touched the cause of the problem.

What's left? Gauge and wire? It seems strange to me that if I'm getting some false reading from the gauge (with two different senders) that it happens in conditions when there is less coolant and air flowing through/over the engine...

Could their be blocked water passages in the block?

Could their be an internal crack in the block which only affects cooling? (no funny smoke or signs of water-in-old are evident).

Could something I installed already be bad?

This is just insane - I should have totally overkilled the overheating problem by this point, and it's as bad as ever.
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  #28  
Old September 26th, 2005, 10:03 PM
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I repeat...recored radiators can and do have problems. A four core radiator isn't necessarily better than the stock three core...because in order to have four cores...each one has to be smaller....smaller fins and so on. In addition....a recore I had done overheated and an inspection showed that when the radiator was built....solder leaked into one of the cores essentially blocking it and causing the overheating at idle in heavy traffic you experience.
That is the opposite of most overheating problems, where the engine is doing lots of work..and can't cool itself adequately. The slow speed overheating problem usually means not enough air is passing through the radiator...or not enough water is being pumped through the system because of low rpm. So, either bad fan (which you have replaced) or the bad recore....ie not enough water flow through the thing because of a blockage.
You can get a handle on this by measuring the temp difference of the water going into the radiator from the thermostat..vs the temp of the water coming out the other side....there should be a signifcant drop...if not...the radiator is the most likely culprit. blah blah I can't remember the maker of the infrared temp device my friend has but finding a mechanic with one just might reveal your problem.
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  #29  
Old September 26th, 2005, 10:31 PM
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There are other possibilities. First, and foremost, I want to know if you are leaking coolant out of the resevoir? If yes, go to step 5. Next, take a napa block tester and see if you have exhaust in your resevoir--if you do, then you either have a porous block or a bad head gasket--since you replaced your head gasket, you probably have a porous block or slipped cylinder--if so, use a block sealant (I wrote up a right up a while ago--just search). If No, goto step 2.

Step 2--are you really overheating? I want you to take an infrared thermometer and measure the temp of your radiator--take off the front plastic grill and get good shots at the core. How high are you reading? Are all the cores the same temp or close (if no, your new radiator probably has obstructions on some rows...it happens) Are you reading above 200F? is yes, goto step 5. If no, goto step 3.

Step 3--There are two possibilities--either your temp gauge is not working (install a VDO temp gauge) or your radiator is not getting hot enough. Take out you thermostat--DON'T ASSUME A NEW ONE IS A GOOD ONE! Put it in boiling water with a thermometer and make sure it is opening alright at the right temp (about 190F). If you see it opening up just fine, goto step 4. If it is not, then put the system back together without the thermostat. Don't worry, we will put a new one in later--just don't forget Go back to begining and restart all tests. If you are back here without a thermostat, goto step 4.

Step 4--Check the cap pressure. Take a bicycle pump or something like that and with the cap on the resevoir and the bike pump hooked up to the overflow valve of the resevoir, pump the system and make sure the cap is letting off pressure at the right point (I forget, but like 15 psi, maybe 18). If it is not right, replace cap. If it is, goto step 5.

Step 5--Let's assume that your temp gauge works and that you are indeed overheating (since the resevoirs are small, this means you will be blowing out coolant--if you are not, you probably have a bad temp sender/gauge). Lets also assume that you are not leaking exhaust due to a slipped cylinder/porous block. One more assumtion is that you have proper fluid flow. So, that leads us to 3 other avenues, IMHO. First is ignition, second is mixture, third is exhaust.

First, what is your timing? Make sure that it is accurate. Is it possible that your timing marks are not quite right? Maybe your distributor is off 180 degrees and it is being forced? Next, what plugs are you using? If your spark plugs are wrong, this could be a culprit--it is more common in motorcycles than trucks, but it can still happen. Verify you have the right plug. While your plugs are out, how do they look? Brown and clean? By running so hot, a too lean mixture might be possible, usually resulting in a deformed plug like it melted or degraded too quickly.

Have you done anything to your exhaust? If you have inhibited the scavenger effect by a ultra low restrictive muffler or oversized pipes, this might (rare) be possible.

Let us know.

Just FYI, I had 3 bad temp senders in my 88 RRC--the PO had the radiator changed, timing...I just changed the sender. The first brand new factory sender was wrong and then I mail ordered one (and they sent the wrong one)--but both times I measured the radiator temp and knew it was not too hot...

Hope this helps. Others please chime in if I made a mistake...

Follow-up Post:

(I tried to edit it, but it said I could not after 15 minutes--could Mr. Administrator just please replace the first message with this edited version?...)

There are other possibilities. First, and foremost, I want to know if you are leaking coolant out of the resevoir? If yes, go to step 5. Next, take a napa block tester and see if you have exhaust in your resevoir--if you do, then you either have a porous block/slipped cylinder or a bad head gasket--since you replaced your head gasket, you probably have a porous block or slipped cylinder--if so, use a block sealant (I wrote up a right up a while ago--just search). If No, goto step 2.

Step 2--are you really overheating? I want you to take an infrared thermometer and measure the temp of your radiator--take off the front plastic grill and get good shots at the core. How high are you reading? Are all the cores the same temp or close (if no, your new radiator probably has obstructions on some rows...it happens) Are you reading above 200F? is yes, goto step 5. If no, goto step 3.

Step 3--There are two possibilities--either your temp gauge is not working (install a VDO temp gauge) or your radiator is not getting hot enough. Take out you thermostat--DON'T ASSUME A NEW ONE IS A GOOD ONE! Put it in boiling water with a thermometer and make sure it is opening alright at the right temp (about 190F). If you see it opening up just fine, goto step 4 (but leave it out...). If it is not, then put the system back together without the thermostat. Don't worry, we will put a new one in later--just don't forget. Go back to begining and restart all tests. If you are back here without a thermostat, goto step 4.

Step 4--Check the cap pressure. Take a bicycle pump or something like that and with the cap on the resevoir and the bike pump hooked up to the overflow valve of the resevoir, pump the system and make sure the cap is letting off pressure at the right point (I forget, but like 15 psi, maybe 18). If it is not right, replace cap. If it is, goto step 5.

Step 5--Let's assume that your temp gauge works and that you are indeed overheating (since the resevoirs are small, this means you will be blowing out coolant--if you are not, you probably have a bad temp sender/gauge). Lets also assume that you are not leaking exhaust due to a slipped cylinder/porous block. One more assumtion is that you have proper fluid flow. So, that leads us to 3 other avenues, IMHO. First is ignition, second is mixture, third is exhaust.

First, what is your timing? Make sure that it is accurate. Is it possible that your timing marks are not quite right? Maybe your distributor is off 180 degrees and it is being forced? Next, what plugs are you using? If your spark plugs are wrong, this could be a culprit--it is more common in motorcycles than trucks, but it can still happen. Verify you have the right plug. While your plugs are out, how do they look? Brown and clean? That leads us to the second--mixture. If it is mixture, you will know. By running so hot, a too lean mixture might be possible, which results in a deformed plug like it melted or degraded too quickly.

Lastly, have you done anything to your exhaust? If you have inhibited the scavenger effect by a ultra low restrictive muffler or oversized pipes, this might (rare) be possible.

Lets re-examine this. You could be overheating by too much heat being introduced into the system, by not enough heat being drawn out, or by bad pressure in the system. If they are not being drawn out, you have obstructions in the cooling galleries of the engine, radiator, thermostat or low pump flow. If they are being introduced and overwhelming the system it is from either exhaust gasses getting into the cooling system, poor timing, or poor fuel mixture. If it is pressure, it is either an obstruction at the resevoir or bad cap pressure release causing wrong boiling point temperature. All these have distinct signs. All these assume you are overheating. I have gone on too long...

Let us know.

Just FYI, I had 3 bad temp senders in my 88 RRC--the PO had the radiator changed, timing...I just changed the sender. The first brand new factory sender was wrong and then I mail ordered one (and they sent the wrong one)--but both times I measured the radiator temp and knew it was not too hot...

Hope this helps. Others please chime in if I made a mistake...
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  #30  
Old September 26th, 2005, 10:39 PM
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What an adventure!

1. Are you still using the stock gauge? If so get a real one - mechanical.

2. Are you losing coolant? If so, check for leaks (black light) or if in the oil. If it's not obvious in the oil you should get it analyzed.

3. Get an infrared thermometer and point it troughout the engine bay. You are lucky in that it overheats while stationary. You can buy one of these with a LCD temp readout but I would rent one that has a video screen where you can see the entire area in color. This will show you the hot spots and cool spots - if you're lucky. If it's hard finding one to rent find a shop that knows how to use one and pay them to do it. You'd be surprised what one of these can do in minutes what it would normally take you hours and days to diagnose.
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  #31  
Old September 27th, 2005, 12:14 PM
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Thanks a bunch for the suggestions - I'll get to work on these. Looks like I'll be getting ahold of a infrared thermometer (I never feel bad spending $$ on tools ) and I was thinking of getting a mechanical temp gauge anyway. I think I'll install an oil pressure gauge at the same time (replace the clock). Does anyone know offhand which sender to use? VDO has several types/threads & I don't know which without taking my idiot light out.

I am hoping that none of the items I bought new are bad, but as mentioned, that does happen and has bitten me before ($250 for a tow and shop fees when it was a bad new distributor cap). I am playing the odds and thinking my temp sender isn't bad because it causes the gauge to behave exactly the same as the one it replaced. But, it's possible.

I'd not forgotten the comment on the new solder-blocked radiator. I was going to take it to a shop to have them check that, but the thermometer sounds like a good idea.

I've not noticed any coolant leaking out the resevoir - only the previously mentioned trickle down the side of the block, which appears to be cured now. I will double-check, though. Interesting - coolant glows in black light? That's easy to check - great to know!

I had a shop pressure-test the system and it appears to be holding pressure properly.

I know I have an exhaust leak near the driver's side O2 sensor - the cat-back exhaust installed by a local muffler shop cut the old pipe near the O2 and welded a new one on - because they didn't want to mess with the very rusty-looking flange bolts. This leak could be causing some incorrect mixture settings (running too lean?) and then overheating. I don't have an EGT sensor like in an aircraft, so I can't know if this is the cause... but, that leak needs fixing anyway & I've been meaning to take it back to the shop who did it. I hope they did not damage the O2 sensor, or had the good sense to remove the sensor when welding so close to it. The exhaust is not drastically unrestrictive - I do have a magnaflow muffler, nothing super special.

I'll work my way down this list and see where it leads - thanks again.
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  #32  
Old October 3rd, 2005, 03:07 PM
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OK, the infrared thermometer that I ordered "2nd day air" has still not arrived, it will be a week tomorrow.

In the mean time, I did notice a new source of leaking coolant - it appears to be the timing cover. My question is, once again: could this be a cause of the overheating, or a symptom of past overheating?

Looking in the attached pics, you can see the newly rebuilt head, and also the dried-up stain from the path down the side of the block where it used to leak coolant from the head. Now, it only looks wet by the timing cover. You can also just see the similarly shiney new water pump in some of the photos.

Whatcha think - cause or symptom? It has to be changed anyway - gasket set ordered...
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  #33  
Old October 3rd, 2005, 03:16 PM
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Well either the head gasket job got a little screwed up or the timming cover has lost it's seal and is now leaking coolant. Are you sure it's not leaking from the water pump?
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  #34  
Old October 3rd, 2005, 03:19 PM
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Depending on where in the timing cover the leak is coming from, it can definitely have an effect. It could possibly be bleeding pressure out of the cooling system through the leak. Or maybe drawing air into the system.

But before you start unbolting stuff, also check the coolant hoses going into the area. There are two heater lines that go into the back of the waterpump. One comes from the heater core itself, the other from the intake manifold. If those connections are leaking it should be pooling on the top side of the timing cover, perhaps in the area of the distributor clamp, before it all drips down.

If you do end up redoing the gaskets, make sure to clean the old surfaces really smooth (I use one of those gasket removing drill bits with the scotch-brite disk), and only use some hi-tack or similar product to hold it in place. Don't use any RTV type sealant, it will just cause problems.

-Hans
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  #35  
Old October 3rd, 2005, 03:26 PM
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Good point - I should replace those hoses, too. It's really hard to see if those hoses are leaking - if they have a crack on the inside/bottom of them I'd never know without pulling them off. Maybe I'll do that first. I can't see any pooling from the topside - there is a small spat of coolant on the new valley pan gasket, but I think that may be from when the heads went back on - it's small and dried-up now, no sign of recent pooling.

I'm not sure it's not leaking from the water pump - hard to see. It's not coming out of the little bleed hole on the water pump/from near the bearing - that's dry.. if it's water-pump related, it's got to be near the gasket mount on the timing cover.

I'm getting fet up with this and I'm starting to just throw new parts at the problem - when in doubt, replace it. Too much time/money/effort has been put in so far, for little results.

I think I'll do the radiator hoses at this time, too - they don't look bad, but are probably factory originals.
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  #36  
Old October 3rd, 2005, 03:30 PM
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Quote:
Originally Posted by jaherring
I'm getting fet up with this and I'm starting to just throw new parts at the problem - when in doubt, replace it. Too much time/money/effort has been put in so far, for little results.
Tell me about it!
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  #37  
Old October 15th, 2005, 10:13 PM
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OK, new data point: accoring to the IR thermometer, I'm getting 6-10 degree difference across the radiator. EG inlet side, 200 degF, exit side, 193 degF. Seems to fluctuate alot overall, but the delta is about the same.

The thermostat housing temp seems to match the top driver's side temp of the radiator (which makes sense). I tried to do tests at the top, middle and bottom of the radiator going from side to side, and if the IR thermometer is accurate, the max drop is 10 degF. It was hard to get a top-left bottom-right reading because the temp fluctuates enough that by the time I got under the truck it's probably not a valid reading.

Overall, this seems bad - I would think the drop should be significantly more. Does anyone know what the delta should be?

The fans pull alot of hot air - I can't keep my had behind them very long. I'm going to have a shop flow-test the radiator this week.

Another thing I noticed: the truck won't overheat with the hood open - I had to close the hood to get it to run up dangerously in temperature. I was at nearly 230 degF indicated on the IR thermometer when I opened the hood and things started cooling back down a bit.
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  #38  
Old October 16th, 2005, 10:59 AM
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I go back to my original assertion. As with my truck, when I replaced the radiator, it turned out that the recore was bad. It had clogged arteries so to speak. Take it back to where you got it...and have it examined. The solder they use to build them is easy to accidentally spill into the core. I don't know, but it might be you ended up having the head gasket problems because the thing was always running so hot...just a guess.
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  #39  
Old October 17th, 2005, 07:55 AM
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I'm with Scott, something is wrong with the rad, my top hose is too hot to grab sometimes but the bottom one is always cool enough to hold. And I have heard of new radiators having a bad core before also.
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  #40  
Old October 18th, 2005, 02:16 AM
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99 disco
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Join Date: Oct 2005
Location: Encino, CA, USA
Posts: 21
remember that your engine is the buick 215 and that the guy behind the parts counter is dumb and cant cross reference anything. So when you buy parts check the part specs between the 3.9 and the 215, this makes things eaiser and cheaper to fix. The ac unit to install is a gm model that is inexspensive, just look under the hood of a series 1 disco.
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