R34 Gtt Getting Hot With High Idle

[Nismo34R]

G'day Everyone..

First happened Yesterday then it just happened again tonight!

So yesterday sitting in traffic my idle jumped randomly from the usual 750 up to 1100/1200. I jabbed the throttle to see if my throttle body/cable was sticking. After the jab on the throttle it went back to the 1100/1200 mark so it ruled that out! My temp rose quite quickly! Nearing the 3/4 mark! I then took off from the lights and pulled straight off the road when I stopped the idle came back to normal and my temp dropped back to the usual halfway point very quickly..

I turned the car off anyway and sat for a good 15 minutes to allow for it to cool down. After I left it didn't happen again.. But tonight it happened again.. It was only over a 90 second period just like yesterday.. Tonight however my idle was up to 1500 then back down to 1100 then back up to 1500.. Up down up down lol

Then I took off and idle went back to 750 at the next lights and temp dropped again to the halfway point.. I really don't want to cook the car so tomorrow I'm hitting the tools!

I'm thinking it's either coolant temp sensor, maybe thermostat(only 18 months old) or clutch fan? I'm not sure about the AAC valve? I was contemplating a smoke test to see if I have an air leak somewhere but the car still boosts fine..

Has anyone else had a similar problem or have any other ideas?

Cheers!

[89CAL]

What ECU does it have?

If the temperature drops when it returns to idle then it does sound like its going to an odd map in the tune for some reason.

[Nismo34R]

89cal it's a factory ecu with a SAFC 2!

[Kinks]

Temp gauge on R33 sits halfway until about 103C. Then it starts rising, I reckon it would show full scale by 110C. operating temp should be 80C (it's an idiot gauge). So if your temp gauge moves past halfway you are already WAY too hot. you did the right thing by pulling over and letting it cool down.

20 bucks says your radiator is blocked or your water pump is f**ked. outside chance of viscous fan failing.

skylines don't overheat unless there is something very basic wrong. high idle will not make it overheat. high idle -> faster fan -> more cooling -> no problem. unless something else is already wrong.

[Ben C34]

Temp gauge on R33 sits halfway until about 103C. Then it starts rising, I reckon it would show full scale by 110C. operating temp should be 80C (it's an idiot gauge). So if your temp gauge moves past halfway you are already WAY too hot. you did the right thing by pulling over and letting it cool down.

20 bucks says your radiator is blocked or your water pump is f**ked. outside chance of viscous fan failing.

skylines don't overheat unless there is something very basic wrong. high idle will not make it overheat. high idle -> faster fan -> more cooling -> no problem. unless something else is already wrong.

Exactly.

I'm pretty sure the ecu raises the idle when the coolant is heaps hot.

[Nismo34R]

The water pump is 18 months old aswell so it surely can't be that? Same as the radiator and hoses!

[89CAL]

I was going to say fan hub but your comment that it cools down when idling normal has got me a bit confused

But what exactly is the gauge (temp) doing when all this happens?

Edited July 20, 2015 by 89CAL

[Nismo34R]

89cal it slowly rises and stops just below 3/4 whilst the idling high. Then once the idle settles it drops quite quickly back to just below the half way point where it should be..

It really has me stumped!

[Ben C34]

Bleed the coolant

[Nismo34R]

Ben, that could be it! Quite an easy and simple fix..

[breaker1845]

Flush your radiator and make sure your thermostat is working correctly for a start. You could have a problem with your water pump failing as you mentioned it happens on idle. 18 months is not a long time but if the parts aren't quality then the bearings in the pump can fail quite easy. Kinks' theory is spot on.

[Nismo34R]

Hey breaker I fitted a genuine Nissan pump! I just bled the radiator and there was a lot of air in the system.. But my radiator level was low aswell ! I might do a pressure test on the radiator/ cooling system just to make sure a welch plug or the water feed line on the turbo or thermostat housing etc isn't leaking.

Anyone have a pressure test kit in Sydney? I'm happy to pay you of course!

[Nismo34R]

Okay guys so a little update! My hunch about the low radiator level was right.

I headed to my mechanic today and got him to do a pressure test on my cooling system and low and behold I sprung 2 leaks!

The first leak which was minor was the radiator drain plug was slightly loose and the rubber deal was gone. After a minute under pressure we counted a mere 10 drops.. That was all sorted and under pressure stopped leaking..

The second leak which was the more major leak was the throttle body bypass hose.. Which would explain the high idle! The clamp was not on and when the hose would heat up it would expand causing the leak which was like a tap trinkling water when a rubber washer is gone.

The clamp was fitted properly back over the fitting, we re-bled the system just incase I incorrectly bled the system, added a little more coolant and all was good!

The car is holding tempreture perfectly, idling beautiful and all seems well so far! If I run into any issues I will repost.

I just thought I'd post up the result for any future references.

Thanks to everyone for posting replies!