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  #21  
Old August 9th, 2007, 01:15 AM
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Looking at the instructions in the workshop manual for removing the intake manifold. Is this a difficult job? I'm a little concerned about the "CAUTION: Place a protective cover over intake manifold openings to prevent ingress of dirt." bit. Sounds tricky.

Also, how would you know that the manifold needs a new gasket?
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  #22  
Old August 9th, 2007, 05:29 AM
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i replaced my manifold gasket when it started leaking. when you pull the intake off the motor is vunerable if you drop something into it. its an easy job to do just time consuming. also you might as well replace your valve cover gaskets when you do the intake. The hardest part is getting all the stuff out of the way to get the intake off. wires and lines etc etc.
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  #23  
Old August 10th, 2007, 12:35 AM
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Truck did not overheat in stop-and-go traffic, ambient temp in the high 90s, but did overheat at the top of a 12 mile 6% grade hill, going up in 4th gear at 40mph, 2200 RPM.

I'm almost certain that the manifold gasket (or anything else) is not leaking. Remaining suspects:

* Radiator: a mechanic installed a replacement radiator back when I was really new to rovers and wrenching. Told me it was monster custom 4 core but I think it's really just a standard OEM radiator. I didn't know any better at the time. Going to take it to the local radiator shop and see what they say.

* Water pump: unlikely, as it's not leaking or making noise at all...but you never know.

* Gears: I'm running 285/75's on stock gearing. Suck-o-rama. Could this be causing my problems?

* Timing: Not sure. Need to buy a stroboscopic lamp and check it out. Don't really know what I'm doing here but I'm gonna read the WSM and try to figure it out.
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  #24  
Old August 10th, 2007, 06:11 PM
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Chris,

I did resolve my issue -- sort of. The original issue was caused by a cracked block. I had a 4.6 salvage motor put in. The motor was gone through, re-sealed, and I had a higher performance cam installed with all of the 3.9 front cover, distributor, 4.2 chip, etc. I also had a 5 core radiator put in and ceramic coated the manifolds.

I say that I sort of solved the problem because I'm having the same problem that was mentioned in another thread by someone else who put in a 4.6 where the motor is running hot (at least that's what the guage says). It smell hot to me, too, but it runs fine and never actually goes into the red. My mechanic measured the temperature and said that it's within a reasonable range, so I'm going to switch out my temp guage to see what I can find there. It makes me kind of nervous to have the needle on the temp guage hovering just outside the red zone under "normal" operation, especially when it always stayed below the 1/2 way point with the original motor until the block gave it up.

By the way, the only way I was able to confirm my issue was to actually have the coolant chemically tested (not just visually inspected).

Devin
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  #25  
Old August 10th, 2007, 10:45 PM
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Devin,

So the coolant test identified the cracked block? I really don't think I have a cracked block or bad head gasket but it's on my list to test if the radiator and water pump check out ok. Out of curiousity, how would one identify a cracked block versus a failed head gasket?

I just received my VDO temp gauge but it's going to take a little work to get it wired up.

Keeping my fingers crossed.
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  #26  
Old August 11th, 2007, 10:25 PM
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Actually, the coolant test only verified that I had some breach that was allowing exhaust gases to mix with the coolant. After opening the motor and inspecting it everything was intact (head gaskets, etc) which narrowed it down to a problem with the block. I had already commited to replacing the motor even if it was only a head gasket because I wanted to go the 4.6 route at some point and I didn't want to spend all the money on the labor for just replacing the head gaskets and I figured I could sell the motor if it was something minor. Unfortunately it wasn't the head gaskets.
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  #27  
Old August 12th, 2007, 12:26 AM
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I've just had a fan clutch fail on my 90... took awhile to figure out how to check that it was really the problem but this is what I did and it worked. Drive it up a hill at speed and get the temp close to the red then pull over and pop the hood. With the engine still running use a piece of closed cell foam or cardboard to try and slow the fan to a stop. You need to do this with some care and keep fingers etc... well away from any moving parts. You drag the foam at an angle that alows it to defect out of the fan. If the clutch is buggered you will be able to drag the fan to a stop. If the fan clutch is working you will not be able to drag it to a stop. The old fan stopped easily but the new one will not stop after driving up the same hill. Temps are now back to normal.
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  #28  
Old August 12th, 2007, 12:46 AM
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I think I have my problem licked. Driving to Ogden and back tomorrow, we'll see how it goes up the hill. I think my problem was a combination of thermostat, fan clutch, and air in the system.
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  #29  
Old August 13th, 2007, 01:11 AM
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Devin,

If you really want certainty on how your engine temp is doing, do as Mike suggested and install an analog gauge separate from the electronic one. Mine has a bulb in the radiator right under the top tube and tells me instantly the temp of the coolant coming out of the engine.

The fan clutch engages at 200 to 205 degrees and knocks the temp down to 195/197 before disengaging. So easy to see. The aux. electric AC fans come on at 218 degrees if the engine is being pushed excessively in hot weather and the mechanical fan can't hold it down, although after working to insure there were no air leaks around the radiator cowl (I have a custom rig due to the 5 liter) I've never seen 218 again. Knock on wood....

DW
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  #30  
Old August 13th, 2007, 01:42 AM
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Crap, my truck is still overheating.

Here are the symptoms:

- It seems to overheat when I pull off the highway into stop-and-go after driving highway speeds for a while.

- Coolant seems to be disappearing. Roughly 3/4 of a gallon over 70 miles

- Coolant is being emptied from the pressure relief valve at the top of the expansion tank when the truck is run at highway speeds

- Expansion tank always stays nearly full. When I fill it only half way and then run the truck, it is full when I check it next.

- Truck stays around 190 - 195 degrees on the highway. When I slow down, it goes up to about 200 deg. If I get in the situation where it overheats, it goes from 200 up to 225 in a matter of a few seconds.

- When it starts shooting up, I shut off the engine at 225 to prevent problems and pull over to let it cool. I release pressure on the expansion tank cap and then I top off the radiator and the fill tube

- Before replacing my thermostat, it would overheat much, much more frequently. You could barely drive to the grocery store w/o it running up.

- I've been very careful to bleed the system, but air always seems to get back into it when the coolant level drops.

- Truck does not smoke and oil looks pretty clean. Need a coolant test to be sure, I guess...


Things I've replaced:

- New radiator about a year ago

- New fan clutch a few weeks ago

- New expansion tank cap a few weeks ago

- New thermostat about a week ago

- New temperature gauge (VDO) and sender as of this weekend

- EE brass radiator/fill tube caps a year ago
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  #31  
Old August 13th, 2007, 04:45 PM
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Thanks, Doug, I think I'll do that. I've already got a VDO in dash gauge and new sender coming that actually has temps on it, but I've heard that a mechanical gauge can be more accurate and installing it as you suggest would be easy to read with the hood open. What gauge did you install -- do you have a pic of where you put it?

Thanks!
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  #32  
Old August 13th, 2007, 05:52 PM
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Chris, you were on the right track. Get the coolant tested for exhaust gas.

All your symptoms would show up if you had exhaust gas blowing into the water jacket and pushing coolant out of the overflow (especially up hills). If it tests positive its a blown head gasket (into the waterway) or a cracked head/block (into a waterway). Id bet on the gasket. If you run it too long the head may need refacing too.


Best
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  #33  
Old August 13th, 2007, 06:03 PM
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Devin,

Sorry, the truck is in Montrose, so no pics. Don't know the brand but it is a common racing gauge maker brand. It has a simple 2" round face, with a bendable copper thermometer tube that runs all the way from the back of the guage (which is mounted just under the dash near the shift lever) through the firewall and up front to the radiator. Think indoor/ourdoor thermometer.

DW
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  #34  
Old August 13th, 2007, 06:57 PM
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Ah, that's where I'd like to be headed!

I'm familiar with the gauge you're talking about, so I'll pick one up.

Thanks, again, Doug!

Devin
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  #35  
Old August 13th, 2007, 07:40 PM
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Quote:
Originally Posted by owen
Chris, you were on the right track. Get the coolant tested for exhaust gas.

All your symptoms would show up if you had exhaust gas blowing into the water jacket and pushing coolant out of the overflow (especially up hills). If it tests positive its a blown head gasket (into the waterway) or a cracked head/block (into a waterway). Id bet on the gasket. If you run it too long the head may need refacing too.
Owen,

Thanks a bunch, that's great info. Question: if it's new head gasket and head resurfacing time, am I better off just buying a new engine?

I've never done a head gasket job myself. I wonder how hard it would be. I guess I'd need some sort of clean room...like my girlfriend's garage?
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  #36  
Old August 13th, 2007, 11:11 PM
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Quote:
Originally Posted by terrapin
Owen,

Thanks a bunch, that's great info. Question: if it's new head gasket and head resurfacing time, am I better off just buying a new engine?

I've never done a head gasket job myself. I wonder how hard it would be. I guess I'd need some sort of clean room...like my girlfriend's garage?
The test comes first to confirm or disprove.

If the coolant tests are negative then you have different riddle to solve!

If the test is positive then check the compression in each cylinder to find out which banks the leak(s) is in. The compression test is simple with a cheap gauge from NAPA swapped in to each spark plug hole at a time with a crank spin on the starter to get the reading. You should see a 20lb or more drop on a leaking cylinder

Its a bit of work but fairly easy to lift the head and see if it the gasket is blown. A workshop manual and maybe a friend who has some experience will be a great help. The blown gasket will be very obvious with a burn-like mark between the low compression cylinder and the water jacket. If it is the gasket you can replace and put it all back the way it came off per the manual with the correct torques. It is rarely necessary to reface the head, just make sure the head and block surface is clean and free of crap from the old gasket. Treat the soft surfaces with utmost respect - dont clean them with a screwriver! If you get everything ready beforehand it can be done easily in a weekend. Just for the heck of it get a quote, you may be 'pleasantly' surprised.

If its not the gasket (look carefully at it, both sides) its the block and time for a replacement short block at least. You will see signs of the problem in the low compression cylinder wall. Then its time to have a few beers and decide on replacing the engine.

...OR you can just spring for a good used 4.6 and a re-chip! There are several available on the web from respectable sources and with a short warranty.

I still bet on the head gasket being the cause.
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  #37  
Old August 14th, 2007, 02:22 AM
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Quote:
Originally Posted by owen
The test comes first to confirm or disprove.

If the coolant tests are negative then you have different riddle to solve!
Well, the test results are in: she's not pregnant. I rented a block tester from Auto Zone (free, by the way) and tested it tonight. Warmed up the engine to 190 degrees where the thermostat opens and put the tester on top of the open radiator which was about 1/2 full with coolant. Squeezed the little balloon thing for about two minutes and the test liquid was still blue. Went inside under the good light and compared the test sample with a control sample from the bottle: same color. Emptied the tester and tried again. Same result. For science's sake, I took the tester back to the tailpipe and sucked in some exhaust. The test liquid turned pale yellow.

So, it looks like there is no head gasket or block leak.

What do you think my next step is? My guess is that I should take it to the radiator shop and see if they can figure out what's going on. I just don't understand where all the coolant is going!
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  #38  
Old August 14th, 2007, 01:35 PM
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Quote:
Originally Posted by Devin W
Ah, that's where I'd like to be headed!

I'm familiar with the gauge you're talking about, so I'll pick one up.

Thanks, again, Doug!

Devin
I had a similar problem, my tests came back positive for exhaust in the coolant (I also had coolant coming out the overflow - superheated coolant problem). I tried all the easy bets - first a head gasket, then a new head... it was in the end a slipped liner -- worst-case scenario, of course, and I went the most expensive route to get there...
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