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Engine Temp Creeping

Gareth87

By Gareth87,
in Engines & Forced Induction

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Gareth87 Community Regular

Gareth87

Posted
Posted

Hi everyone,

I've got an annoying problem with my FJ20. Ever since i did a full engine build on it, i have had temp creep issues at idle.

Its runs normally while driving at around 80-82 degrees with the thermos coming on at 82. However, it generally won't pull the engine temp back at idle. The fans will only just hold it at temperature or in traffic or a warm day, it will creep up slowly.

I run a 10 and 12 inch curved blade fans and a 3 core radiator which i have had completely stripped and rebuilt. (helped a little bit) The back of the bonnet is also lifted but i still find myself looking at the temp gauge creeping up slowly.

The fans don't run any shrouding so that will be something i will try to sort out and try.

Could anyone recommend anything else to try to help bring the temp down at idle?

Also, will a turbo beanie help? I run a big top mount turbo and gate and it pumps out some serious heat which is no doubt sending under bonnet temps sky high. but will this cause water temp to creep up?

Thanks in advance.

Gareth

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Gareth87 Community Regular

Gareth87

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much bigger cams, head work, forged pistons, rods, external oil pump setup.

The only thing i think could make it temp creep to do with the engine would be the head work and bigger cams as its a fairly lumpy idle and idles around 1000 rpm.

Water pump was a new standard part.

Interesting you say lifting the bonnet makes things worse.. wouldn't that vent hot air?

paulr33 Grand Master

paulr33

Posted
Posted

no i believe the bonnet is setup like that and makes a pressure zone

i dont remember the physics behind it, but i think raising the bonnet makes it worse for temps

did you raise the bonnet at same time of engine rebuild?

blind_elk Grand Master

blind_elk

Posted
Posted

Raise the cut-in temp of the fans. There is no point fitting thermo fans that run basically all the time. All you are doing is shifting the load on the engine from a factory fan to the alternator. The cut-in can be as high as 90 C, or even higher - the motion of the car will control the engine temps; the fan is just for those times when the engine gets a bit hotter because the car isn't moving, or is moving too slowly.

As for the temp increasing at idle, are you sure the fans are running the right way - pulling air through the radiator into the engine bay (I'm assuming you have had to mount the fans on the engine side of the radiator).

Ordinarily, having a raised rear of bonnet is only a problem when the car is moving - there is a high pressure region created at the base of the windscreen (that's where comes from for the heater / a/c in the cabin). When the rear of the bonnet is raised, this high pressure region feeds a high pressure into the engine bay, and that restricts air flowing through the radiator to cool the engine. (you should recall from high school physics that air moves from regions of high pressure to regions of low pressure; if the inside of the engine bay is already at a high pressure, then air from in front of the radiator won't flow towards that region)

Kinks Grand Master

Kinks

Posted
Posted

shroud should make a massive difference. otherwise you're just circulating hot air around the engine bay not actually pulling it through the core.

raised bonnet may help *slightly* when stopped but when underway it will do nothing as the base of the windscreen is a high pressure area and you will not get any air being removed once you're moving. for best cooling when moving you need a sealed bonnet and your underbody plastic guards - these make a vacuum behind the radiator and help suck air through.

for cooling when stationary you need a powerful fan (engine driven, not electric) and proper shrouding. and a decent radiator which you've already got.

GTScotT Grand Master

GTScotT

Posted
Posted

From the mouth of one of NSW best known CAMS officials, raising the bonnet hinders cooling ability. As Paul said the windscreen is a high pressure zone and would alter the airflow through the engine bay while having it propped up.

This should be changed back to normal however I do not think this is the source of your problem. I believe you have airlock in your head (poorly bled). The other thing I have seen with alloy radiators are the tubes expanding and not letting any air through.. While they still flow fine they do jack all for cooling. I have generally seen cheap alloy rads to SUCK at cooling regardless.

Recommend swapping to stock radiator (for test) and being very careful while bleeding coolant. GL

Gareth87 Community Regular

Gareth87

Posted
  • Author
Posted

Thanks for all the replies everyone. It definitely seems as though i will drop the back of the bonnet back down. I did that recently to try but only seemed to delay the onset of temp creep while stationary. Did nothing while moving.

The radiator isn't alloy, its a standard radiator for the model car with an extra core and it's bled for certain.

The temp sits around 80 when driving but when stationary in traffic it will climb into the 90s and i have to keep moving for it to come back down. So to me it has to be an airflow issue i would have thought. I know its not huge temps but if i eft it to sit there... it would keep climbing.

The fans are on the engine side and like i said, with no shrouding, so i think dropping the bonnet and building a shroud will be a start.

Anything else??

Thanks for the input, some interesting points there.

FJdat Contributor

FJdat

Posted
Posted

like everyone else has said, the fan shroud should help.

Also check the timing at idle.. sometimes retarded timing at idle can cause the temp to rise at idle.

What CFM are the fans rated at?

Was the radiator cleaned and flushed after the engine was run in?

Gareth87 Community Regular

Gareth87

Posted
  • Author
Posted

Ok ill suss the timing.

The fans... i have no idea what CFM they flow. Cant find anything on them to tell me either.

Yes the radiator was cleaned and flushed after run in.

Has anyone found turbo beanies to reduce engine temp or creep?

G

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