Over heating issues on new 4.6 build - Defender Source
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  #1  
Old July 29th, 2007, 10:53 AM
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Anthony Leung
1995 D90SW #51
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Over heating issues on new 4.6 build

I just replaced my POS 3.9 with a 4.6 with an after market comp cam, new lifters ect. I'm having issues with the engine running hot, i have already recored the radiator with a 5 core. Not sure what it would be at this point clutch fan was also replaced. An oddly i'm not having issues running in 4L running slow most of the over heat issues are more constant 3-4K RPM range at highway speeds. Was wondering if anyone else who's done this swap has had this issue and what did you do to repair the issue. I am tempted in cutting vents into the hood which alot of members have done it seems. But i would like to find the issue before i cut.
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  #2  
Old July 29th, 2007, 03:37 PM
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Chris Davis
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I basically have your setup with the exception that I am running electric fans. My overheating was related to exhaust gases making their way into the coolant. I have a block tester from Napa if you want to check yours out and at least rule that out--I am in Boulder but work in Denver so we could always meet up sometime.

There are a lot of possibilities including inadequate flow of the coolant through your system. You can help check this by using a infrared thermometer and checking the temperature at different levels in your radiator and hoses and kind of (not really accurate) get an idea of your temperature gradients. This will at least tell you if you have hot water entering the radiator and cooler water exiting.

These two tests should at least be able to point you in the right direction. Other things to check are properly bled air from cooling lines, engine timing, your thermostat and the coolant pressure cap. These will be the most likely culprits.

Let me know if I can help.
Chris
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Old July 29th, 2007, 10:48 PM
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jim pendleton
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Vacuum advance working? Did you degree the camshaft? You may have to play with your timing and ignore the factory setting. Move it a degree or so and test drive a few times. Do you have A/C? Is the condensor clean enough for air flow. Can you install surround pieces to direct airflow through the radiator and keep it from bleeding past it or recirculating from the engine compartment?
Checking for exaust gases is a good idea as well. Need to rule that out on a new engine also.

Some things to consider.

JP
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  #4  
Old July 29th, 2007, 11:24 PM
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Hans Haase
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I'm with Pendy, timing may be the issue and I've seen it happen a few times with recently rebuilt engines if the timing is really wacky. Since it's happening when the engine is under load, that lends a bit more to the theory of the vacuum advance in the distributor to possibly have failed, either the vaccum can itself or the lines leading to it.

However, also don't rule out a mixture issue either, as running lean for extended times may also cause overheating. Are you using the original injectors and computer from the 3.9? You may need to rechip and go with a higher flow rate injector, to go with the bigger engine... especially if you've done the cam. Got a Fuel/Air meter in there at all? May not be a bad idea, especially if you can spring for a wideband one that can do a data plot for you.

-Hans
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  #5  
Old July 30th, 2007, 01:51 AM
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Anthony Leung
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Thanks guy's i'll give it a shot, Davis i'll pm you if i can borrow the tester. The cam has already been advanced 3 degree's but maybe it's too agressive. The water pump is actually new as well, and water flow seems good, no real way to test how much flow there is though. I've already poked around with a infared thermometer. I have not swaped out the chip on the ECU yet which might be some of the cause . Going to put a 4.2 chip in but there not so easy find anymore.
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Old July 30th, 2007, 05:29 PM
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Chris Davis
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I am running the 4.2 chip in my ECU. I currently run 10 degrees of timing, and again, running just fine temp wise...
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  #7  
Old August 1st, 2007, 01:39 AM
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Ben
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find drillbit on DWEB, he has some 4.2L ecu's I think?
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  #8  
Old August 1st, 2007, 02:32 AM
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Anthony Leung
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funny, that's where i got the block from =)
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