Overheating On Idle

[battery]

hey guys got a little overheating problem.

so i put an rb25 in my r32 a few months ago and have had this problem since then, its fine on the freeway sits between 77-80, then when i am sitting at the lights it will slowly rise the most i have seen was 95 degrees...

so first off i tried a bottle of mukout, the engine had been sitting around for a good year so i thought the galleries might need a clean out, no change.

i have done the following and have not noticed a change.

- new waterpump

- thermostat

- big 52mm alloy radiator

- multiple flushes

one observation i have made is if i leave the top hose off or look at the water in the radiator i get no water flow on idle, if i rev the engine it pours out and the water temp lowers.

what causes this??

as far as bleeding goes i think i have done enough, would air in the system cause this overheating problem im having?

[White GTS-T]

Yes.

[Moodles2]

Do you still use the factory viscous fan + shroud.. the shroud is important with temps

[battery]

Do you still use the factory viscous fan + shroud.. the shroud is important with temps

yes i did have it on but im not using it on the new radiator, its irrelevant anyway the reason its overheating is because there is no flow through the radiator at idle and i have no idea whats causing it!!

im thinking a pressure test on the cooling system is the next step?

[mad082]

could possibly be that the new water pump was dodgy.

[battery]

could possibly be that the new water pump was dodgy.

nope the old pump i pulled did the same thing and it was in good condition.

[stefan.o]

maybe it requires a different thermostat, i went throuhg two before i found one that worked, maybe the fans arent strong enuf for the radiator or maybe they're drawing the wrong way (not being smart but ive done that before lol).

Thats all i can think off???

Or maybe its done a head gasket???

Edited December 1, 2009 by stefan.o

[steve12]

Remove the thermostat and see if it still heats up at idle. Best to check this on a warm day. This will tell you if it is restriction by the thermostat itself.

I think some open up more than others. You may still have gunk in the cylinder head and this with the same amount of restriction from the thermostat may be stopping the flow at idle.

[battery]

i doubt its the thermostat because the one that i have in there now is a shitty aftermarket one and it opens very early about 64 degree's then when i stop up up it goes then when moving back down to 64ish.

when i swapped them i had just switched the car off then while it was still at operating temp i took the thermostat out and it was still open then began to close...

so im pretty sure its not the thermostat, water pump, radiator or fan.

if i hold it at 2000rpm the water will flow and the temps drop so to me it seems as though it can only be a restriction in the block/head?

next im gonna try removing the thermostat and sticking a hose in there to try and flush the shit out then run the car without the thermostat for a while just to be sure!

[mad082]

yeah it sounds like some sort of restriction/air bubble. have you properly bled the system using the air bleed screw?

as you said, pull the thermostat out and shove the hose in there and try and flush it out with pressure.

[08yannch]

i dont know just throwing it out there what type of pulley have u got on the water pump. maybe the water pump is not spinning fast enough at idle. the larger the pulley the lower the speed off the water pump.

[GTR-N1]

"Fan Clutch"

http://en.wikipedia.org/wiki/Fan_clutch

4th paragraph will give you the symptoms you described.

[blind_elk]

Terry, he's not running a fan. And that will explain everything. No fan, no air moving through the radiator. No air moving through the radiator, no cooling.

[battery]

i dont know just throwing it out there what type of pulley have u got on the water pump. maybe the water pump is not spinning fast enough at idle. the larger the pulley the lower the speed off the water pump.

yeh interesting theory but im pretty sure theres only one size.

Terry, he's not running a fan. And that will explain everything. No fan, no air moving through the radiator. No air moving through the radiator, no cooling.

i'm running the stock clutch fan and shroud with a 52mm radiator, this all has no effect anyway im not getting flow, even if the coolant in the radiator was 1 degree it wouldn't help as its not flowing through at idle.....

[blind_elk]

Then what the hell does this mean?

yes i did have it on but im not using it on the new radiator,

Either you are using the fan or you aren't using the fan.

If you keep changing the story, we can't possibly help diagnose the problem!

[battery]

Then what the hell does this mean? Either you are using the fan or you aren't using the fan.

If you keep changing the story, we can't possibly help diagnose the problem!

i was referring to the shroud.

[blind_elk]

Well then, maybe you need to use the shroud.

I've installed a RB25DET in my R32, and even with a standard radiator, standard clutch fan, standard shroud, I don't have any problems with overheating at idle.

[Moodles2]

Use the shroud, I've read people have switched to twin thermo fans and it just didnt compare to the factory viscous fan + shroud

[Carbon 34]

"Fan Clutch"

http://en.wikipedia.org/wiki/Fan_clutch

4th paragraph will give you the symptoms you described.

fan clutch, is common for lines to fail, but easy to test , search for it, I wrote a how to test article on here for it a while ago

the thermostat was placed in backwards ???? some cars they can be ?

did you burp the system, the two bleeds on the plenum and near thermostat area. and squeze the top and bottom hose when cool to and cap off to rid the air lock in the head ?????

turn on the heater full heat ...fan on when filling coolant, to rid the air lock in the heater core ?

do not use plain water ,, unless your motor blew its coolant on the road and you need to get home. it boiling point is too low and crusty engine insides.

dont mix coolant , never

water pump, failure, or bind up ???

you will overheat without the shroud in traffic

use Redline water wetter or Motul socool products when sorted out, it makes a huge difference

worse case,backflow the system with garden hose and flush it out,

if you took off the head ,, did you check the gasket isnt blocking the water galleries ?????

[battery]

no more talk about the stupid fan or shroud, this is not the issue i have tried all configurations and there is no difference.

i also doubt its a bleeding problem, in my experience even without a bleed the air will eventually find its way out of the system as long as you keep coolant levels topped up.

when i get some time ill reverse flush it with a hose.