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  #1  
Old October 24th, 2005, 07:40 PM
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overheating w/ everything new

Yes Iv'e read all the posts on the "saga" but my new problem has me at a complete loss. I drove to San Fransisco this weekend and had some random overheating issues, when going down hill, or up hill and at night. I didn't have much time to mess around I was in a time crunch so I took the thermostat completly out, because I thought it was hydro locking since the thermostat is brand new and I did not drill the hole. So it obviously took a while to warm up but once it reached normal operating temp I got back on the road. Now it still occasionaly overheats, up hill down hill does not matter. the engine also NEVER gets cold while on the road, I drove over donner pass last night it was freezing and was still running hot.

Just for reference it has and 3.9l 115,000mi, new radiator, valvejob/headgaskets 3000 miles ago. I just replaced before I left: new hoses, new fan clutch, new water pump, new belts, and new thermostat but it now has NO thermostat in.

My question is shouldn't the engine at least get cool at some point with the thermostat is out? What the hell could be causing the engine to overheat? everything is new...is it dying?

Thanks guys
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  #2  
Old October 24th, 2005, 07:44 PM
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Did you say a new radiator? Sometimes they leave the factory bad. I would check over the radiator for cool spots or have it flow tested. DOes the cooling system seem to be holding pressure? Could the timming be advanced too far?
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Old October 24th, 2005, 07:56 PM
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The radiatior is about 3-5000 miles and it worked fine from the get go. but a flow test may be in order. I'll check the timing, but it's running fine and havn't messed with it in months. How would I check if it is holding pressure at home? it never boiled over, and has zero leaks.
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  #4  
Old October 24th, 2005, 08:03 PM
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after running for a little while shut it off, when you oen the overflow tank there should be a relife of pressure, it should hold that pressure overnight. IF you have an IR temp gauge you can check for cold spots on the radiator, that would tell you if there is any blockage.
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Old October 24th, 2005, 08:40 PM
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Mike your the greatest, I'll give it a try tonight. There is pressure release when I pop the over flow, It also starts to boil, so I bet there is pressure.
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Old October 24th, 2005, 08:49 PM
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hmmm, shouldn't be boiling unless it is running REAL hot. I hate to say it but maybe a hydrocarbon (I think thats it) test kit is in order just to rull out the headgasket. The test kit is cheap at any local parts store.
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Old October 25th, 2005, 01:43 AM
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Also, check your timing... the 3.9 is very sensitive to that I've found. Do you have a/c? If so, check that the A/C fan is running properly too.

Still got the old fan clutch? Maybe try putting it back in?

-Hans
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  #8  
Old October 27th, 2005, 08:54 PM
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Well, here's how you can check out the radiator question. I noticed with mine that I was only getting a maximum 10 degree temperature drop across the radiator. That is bad. The little IR thermometer comes in handy - borrow someone's or get one and check out your radiator.

A local shop that does high-performance engine work told me that the drop should be at least 10 deg F. If not, you have one of two problems:

1) radiator is plugged - generally, this means you overheat more under load

2) not enough airflow across the radiator - this means you overheat when sitting still

These assume a properly designed system. From my talks with this guy, mine may not be (yes, still getting the overheating problem). If yours is all stock, see above.

The radiator replacement I got was a 4-core, standard-density radiator. That used to be the easy answer back in the musclecar days - 4-core it! However, as it turns out, a standard (eg non-high efficiency) radiator is almost pointless to have made as a 4-core because the air temp is almost certainly too hot by the time it reaches the 4th core to do any good. I was told that I should have gone with a high-efficiency radiator core, and then only go to three cores. The radiator is retaining too much heat - it is able to bleed alot, but needs massive airflow to make that happen. I'd hate to think I tossed away a few hundred dollars on that...

Second potential problem. I added electric fans after the clutch was seen to be bad (and electrics were not much more than the cost of an LR replacement clutch). In theory, they should pull more air than the factory clutch fan - I have more 'spinning area' than the original fan did. But, they don't have a true 'shroud' which pulls air through the entire surface area of the radiator. Because this monster 4-core is so thick, alot of volume of hot water is not getting cooled when at idle because not any air is getting drawn through, say, 20% of the surface area. This is probably aggrevating my problem above.

So, that might be my problem -- certainly, a 10 degree drop is bad bad bad.

Timing is also a problem for me ever since I had my heads redone. I can only think that the shop had to shave them down to get them true again, because now I have detonation like crazy and have to use 91 octane gas, even with an extra 3 deg retarding I still get some pinging under load (moreso on a hot day). Well the other problem could be some other reason that I'm leaned out now - running too lean leads to detonatino and overheating. Those causes could be problems with the EGR valve, O2 sensor, etc.... but regardless of this second potential problem, I definitely have some issue with my radiator because of the small temperature drop...

Follow-up Post:

By the way, we have almost the same engine now - new heads, just over 100K on the bottom end, and everything else cooling related is new.
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Old October 27th, 2005, 11:02 PM
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Jason, do you think yours is running too lean as well? That should all be controlled by the computer, and unless you re-chipped it then it shouldn't be an issue. Using a US tuning resistor on the computer gives a fairly rich mixture normally. In fact when I had the issue going on with my cats being empty and failing inspection the machine was giving me some really high numbers for hydrocarbons, even by non-cat standards. The only reason it would be going lean is if your injectors are clogged and unable to get enough fuel to the engine at all. But that would probably trip a trouble code at that point since the sensor readings would be out of whack.

Also, Steve, which headgaskets did you use? The shim-steel gaskets just plain suck IMHO. If you used those and didn't get the heads shaved, then you might still be having headgasket issues with air bleeding back into the cooling system. The steel gaskets are nothing but trouble, the composites seal a LOT better. As Jason mentioned as well, using the steel gaskets AND shaving the heads also causes the compression ratio to get way too high. When I put the composite gaskets in mine I was able to drop down to 89 octane and it's never had any pinging since the new gaskets.

-Hans
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  #10  
Old October 28th, 2005, 12:10 AM
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Quote:
Originally Posted by jaherring
A local shop that does high-performance engine work told me that the drop should be at least 10 deg F. If not, you have one of two problems:
Pardon my ignorance, but what exactly do you mean by a drop "across" the radiator? Are you referring to the difference in temperature between the inlet and outlet? I'm new to Rovers and car mechanics in general but I'm trying to learn. My new Defender has overheating issues that are being caused by, I think, a leaky radiator. For my edification, could you also explain (or point me to a resource explaining) what a head gasket does and how it interacts with the cooling system?

Back to hiding under the rock...

Chris
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  #11  
Old October 28th, 2005, 04:30 AM
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Quote:
Originally Posted by terrapin
Pardon my ignorance, but what exactly do you mean by a drop "across" the radiator? Are you referring to the difference in temperature between the inlet and outlet? I'm new to Rovers and car mechanics in general but I'm trying to learn. My new Defender has overheating issues that are being caused by, I think, a leaky radiator. For my edification, could you also explain (or point me to a resource explaining) what a head gasket does and how it interacts with the cooling system?

Back to hiding under the rock...

Chris
yes, the temperature drop from the inlet side (hot water from the engine) and the exit (return to the engine) should be 20 degrees F or more. Mine is never better than 10 deg F, so I *know* I have a problem there somewhere - either airflow (which the radiator shop seems likely) or the radiator itself.

The IR thermometer is a great tool to check this, but a good radiator shop will have other types of gauges to measure this (with probes, etc).

Follow-up Post:

Quote:
Originally Posted by Hans
Jason, do you think yours is running too lean as well? That should all be controlled by the computer, and unless you re-chipped it then it shouldn't be an issue. Using a US tuning resistor on the computer gives a fairly rich mixture normally. In fact when I had the issue going on with my cats being empty and failing inspection the machine was giving me some really high numbers for hydrocarbons, even by non-cat standards. The only reason it would be going lean is if your injectors are clogged and unable to get enough fuel to the engine at all. But that would probably trip a trouble code at that point since the sensor readings would be out of whack.

Also, Steve, which headgaskets did you use? The shim-steel gaskets just plain suck IMHO. If you used those and didn't get the heads shaved, then you might still be having headgasket issues with air bleeding back into the cooling system. The steel gaskets are nothing but trouble, the composites seal a LOT better. As Jason mentioned as well, using the steel gaskets AND shaving the heads also causes the compression ratio to get way too high. When I put the composite gaskets in mine I was able to drop down to 89 octane and it's never had any pinging since the new gaskets.

-Hans
It could be running lean - I was looking at some diagnostic information for engine pre-ignition, and one reason it can occur is running too lean. This could be a messed up EGR, faulty O2 sensor, or other reasons. Running lean causes pre-ignition and causes the engine to run hotter - both issues I have right now. However, I think they are two separate problems.

I think I may have a higher compression situation (shaved heads, and yes, I have the steel gaskets) happening causing the the problems with pre-ignition and in particular 87 octane gas. I didn't know about the difference between the composite and steel gaskets - so I got what was on it originally. Ooops.

I used to run 87 octane all day long without pre-ignition problems before I had the heads done. Now I have to run premium (and, by the way, the mileage is not one bit better)
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Old October 28th, 2005, 08:25 AM
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Anyone thought about swapping out the waterpump? In my commuter car the preventative maintenace recommendation is to change the water pump at around 100k miles.
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  #13  
Old October 28th, 2005, 10:03 PM
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Thanks for all the help guys, I think a lot of us have these probloems.

I did use the composite gaskets. The radiator temperature is realtively even across it. I think it is flowing fine. I have a felxilite pusher for when the truck id idleing in the heat... so the fan at slow speed issue dosn't get it hot. I also have the shroud for the regular viscous fan intact.

I took her out on the trails today and it never ran hot, keep in mind that it was 39 degrees F and there is still no thermostat, it never ran cold but still never hot. So it seems to only get hot during long hauls...what could that mean?

I'm going to get a hydrocarbon test and see if there is a head problem. I have never done one before.. any pointers or is it sraight forward??

I keep ya'll posted.
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Old October 28th, 2005, 10:33 PM
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Yeah, the only consistant issues with Defenders seem to be cooling and oil cooler lines.

I personally think that the radiator is too small for the truck and doesn't give much of a buffer of excess capacity like it should. It doesn't take much of a problem to have the engine exceed the cooling capacity. Adding to the problem is the having the oil cooler taking up space and adding extra heat to the radiator.

Then you have a near total lack of ventilation for underhood hot air to escape. Most other cars I can think of had some kind of ventilation along the back edge of the hood for airflow. I've been considering putting some louvers or maybe an electric fan under the hood somewhere to pump that hot air out, as well as a separate oil cooler to give another way to get the heat out of the engine.

-Hans
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  #15  
Old April 3rd, 2006, 07:52 PM
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So Jason, what did you ever figure out? It's finally getting warmer up here, and my temp climbs above 1/2 way, but never spikes. Gets wamer up steep hills, but again, doesn't spike. I've replaced the thermostat and fan clutch. Top hose is pressured up and too hot to touch. There's a bit of pressure in the overflow, and I'm not loosing coolant.

My bet is radiator, but there aren't exactly any shops around here that specialize in them.

And my stock electric fan NEVER comes on.
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Old April 4th, 2006, 08:13 AM
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May be a silly thought, but could it be a bad temp sensor or gauge?
I had a bad ground on the 110 that gave high temp reading, but when I measured the temp it was fine........
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Old April 4th, 2006, 08:17 AM
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I was wondering about the sensor. I would think that it would start to boil over at the 3/4 mark, but maybe not. At what point should the stock fans come on?

I'm going to either find someone with an IR temp sensor and check it, or go the 40 miles to the rad shop.
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Old April 4th, 2006, 09:38 PM
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Does anyone know at what temp the stock fans should come on?
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Old April 4th, 2006, 10:18 PM
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Stock electric fans only come on with the AC or at around 210 or so I believe. I know you can get a lower temperature switch, from an older VW, I've been using one for my Flexalites. I have to get a new one soon too, as mine is busted. I'll see if I can dig up the part number if you want.

-Hans
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Old April 5th, 2006, 05:49 AM
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Quote:
Originally Posted by Hans
Stock electric fans only come on with the AC or at around 210 or so I believe. I know you can get a lower temperature switch, from an older VW, I've been using one for my Flexalites. I have to get a new one soon too, as mine is busted. I'll see if I can dig up the part number if you want.

-Hans
I thought that might be the case with the fans and AC. I need to cover the basics and I'm still looking for someone with an IR temp reader. That will set me on the right course, and I think it will probably be the radiator.

Thanks for your input.
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