HELP Overheating Diagnosis!

roverguy10 · 30th November 2009, 03:33 AM

My truck has me good and stumped. Lately, it has been acting up in the worst sort of way - it is overheating when under load.

I replaced the thermostat first thinking it was that, and radiatiator (unrelated issue). It will not overheat when idling, but when it is driven the guage climbs to infinity, but as soon as I stop and let it idle, it will slowly climb back down over time. I know the guage is accurate, because I have measured the actual temperatures at vaious points using my infrared thermometer.
Today I ran a compression test and compression leakdown test, and the results do not point to a leaking head gasket, I get an average of 7% leak and 140psi compression. No 5 cylinder has the lowest compression and highest leak, but it seems to be from the intake valve not completely sealing - air was slightly leaking out of the intake no matter where we tested the cylinder in the 3 strokes it should be closed.
The viscous coupling appears to be working properly, but other than seeing how hard it is to turn when the truck is hot vs cold I don't know how to check it. (I replaced it about a year ago, 7k miles).

I really need to determine if I am getting exhaust gasses in the cooling system when under load so I can determine if it is internal engine or external issues. Anyone know what the best way to test for exhaust gasses in the cooling system when it's under load?

**Sprint** · 30th November 2009, 06:57 AM

there is a test kit you can buy from repco, etc that contains the equipment to test the coolant for the residue of combustion gasses, probably cheaper to get a workshop to do it tho

**seano87** · 30th November 2009, 07:22 AM

Originally Posted by Sprint

there is a test kit you can buy from repco, etc that contains the equipment to test the coolant for the residue of combustion gasses, probably cheaper to get a workshop to do it tho

I'm not sure they have Repco in Guam!

But as Sprint suggested, a good mechanic should have the equipment to test it, or will know a place that does.

Good luck with it!

mike 90 RR · 30th November 2009, 10:01 AM

You wanna comfirm which truck & motor, your on about??

Considering the place is the size of a postage stamp ... I'm surprised that it even get's to temp before you get to the other side ....

Is the truck from US soil?? (import)

Mike

**discowhite** · 30th November 2009, 11:16 AM

my guess if its a rover EFI is the fuel pressure reg or injectors.

mine did the same thing, only getting hot under load up hills etc, cruising around town no issue.

it ended up being low fuel pressure due to a dead reg. low fuel pressure and high load = lean fuel mix = hi temps.

cheers phil

ps i did all the radiator etc first as well

**roverspec** · 30th November 2009, 11:40 AM

Hi,

If this is a TD5 there is a problem with the Head gasket moving and overheating. once you get the new head gasket and locating dowels, there is no more plroblems. better get done quick so you dont risk damaging the head.

carla

**Blknight.aus** · 30th November 2009, 07:06 PM

whats it do after youve got it hot and hold high Idle in nuetral?

cool down faster nor not at all?

I'll open with poor coolant flow

**Blknight.aus** · 30th November 2009, 07:16 PM

I was going to post this up as an edit... (since I worked out it was a td5 after I replied..

dont faf with it, pull the head and get that valve sorted and the faces checked for tolerance.

second guessing overheating faults on a td5 can go from asking "I wonder what could be causing this to warm up occasionally" to "A new engines going to cost me HOW MUCH?" very very quickly and unexpectedly.

The td5 while as an engine is a wonderful thing she is a harsh mistriss who will whip your wallet if you dont look after helping her keep her cool

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