Rb25Det Neo Water Temp Problem

[Guishnu]

Hi all,

I have a problem and wondered if you can give me your thoughts please.

I have a 1998 R34gtt with about 70,000 miles and running a GT3076r and a Link G4 plug and play ECU running a 5 bar map sensor. It's been mapped on a dyno dynamics rig to 498hp at the flywheel. Internally it's stock apart from a 1.6mm metal head gasket. (Fmic, oil cooler etc) I have done 9000 miles with the car in this spec.

The problem:

Yesterday the water temperature started to climb, which also caused the oil temps to rise. General overheating occurred which resulted I'm a peak temp of 101 deg oil temp and 120 deg water temp before I shut it down. It will cruise on the motorway off boost for quite a while (70+ miles) and stay under 100deg water temp and about 85 deg oil. However, when you hit roundabouts or built up areas and speeds below 40mph she starts to overheat, heat soaks everything and it's all over. The top hose feels hard.

I pulled the thermostat and that's working properly. I pulled the water pump and that's perfect too. I have re-bled the cooling system and that's got no air in it either.

I think that the head has lifted and probably caused gasket failure between the water passage and cylinder or I have somehow cracked the head. But can anybody else give me any better ideas?

Cheers

Chris

[Dale FZ1]

when you hit roundabouts or built up areas and speeds below 40mph she starts to overheat, heat soaks everything

I think that the head has lifted and probably caused gasket failure between the water passage and cylinder

Is the radiator fan operating correctly? Assuming the OEM fan and shrouds are all in place.

Do you have evidence of coolant in the engine oil, or oil in the coolant?

[JonnoHR31]

get a local radiator shop to do a co2 test if you suspect the head.

otherwise check radiator, flush it out etc and see if it helps.

[KiwiRS4T]

Go to a radiator shop. A simple pressure test should show any leaks. If none get the radiator cleaned out or recored

[Guishnu]

Hi all,

Thanks for your reply.

No shroud, big alloy 75mm radiator that's been perfect up till now.

No evidence of oil/water contamination. No mayonnaise etc.

[GTSBoy]

Head/gasket failure does not automatically imply that the two liquids will mix. What your symptoms suggest is that combustion gases are getting into the coolant. Follow the recommendations above.

[pipster11]

probably the radiator

mine (50mm jjr one) got clogged (flushed the system with the cleaner stuff before i put the new rad on, but it just loosened it all up and eventually washed it into the new rad)

see if you can get it cleaned out

i ended up getting a new stock size rad off ebay (koyorad) for about AU$220 (the top tank split on my old stocker, hence the new alloy one)

[Moodles2]

Factory fan + no shroud, has been proven to be the source of overheating for most people who have problems with overheating (having no shroud)

[Guishnu]

Yep,

Pretty much what i thought. I'll do a sniffer test then if it comes up bad, tear it down.

Thanks very much for your help everybody.

Chris

[Guishnu]

Okay now I'm totally boggled.

I have done a block test and it's come up clean, I have done a compression test and it's come up at 140psi (give or take) right across the board.

Oil is good, water is clear...

Took it out for a drive and boosted it to 1.4 bar. No problems until it got hot. When its at good temperatures it boosts fine, when it gets hot!- its almost like it hits a boost cut or is blowing out the spark when it hits high boost and WOT.

Engine doesn't overheat when standing idle ticking over - warms up correctly. Doesn't increase in temperature when already hot/overheating when then left to idle.

Plugs looked a good colour, not black or sooty, not white or charred. A nice light brown colour.

Drives perfectly fine off boost. ECU doesn't throw any other fault codes.

Engine doesn't smoke or pop balls of smoke in any way.

Does anybody have ANY idea? I'm utterly stumped.

Could the turbo be on its way out and cooking the water? It's only 10k miles old and doesn't make any noise or smoke?

Somebody mentioned that when the bearings are really warn they cause excess heat? But wouldn't this happen when just driving normally off boost too?

I really just have no damn idea.

[Bsa]

Do a leak down test sounds like hg I recently bought a 26 with a busted head gasket was running fine just getting hot pulled the head off and the gasket was gone. Replaced it did a leakdown and cam back perfect results

[JonnoHR31]

try and do a compression and leak down test while its hot

[msports180]

My 34 did something similar, ended up being the radiator was heavily blocked.

[NISMOGTT]

My 34 did something similar, ended up being the radiator was heavily blocked.

Agreed... i had a similar issue in a previous car and found the whole bottom half of the radiator was blocked

[TTT]

In terms of cost and ease, you'd be better of trying to put a stock radiator in and retest (put the shroud back on too with the stocker radiator).

much quicker, cheaper and easier than pulling the head off.

Radiator cap in good condition?

New ones from Nissan are pretty cheap.

Edited April 2, 2012 by GTST

[gotRICE?]

Took it out for a drive and boosted it to 1.4 bar. No problems until it got hot. When its at good temperatures it boosts fine, when it gets hot!- its almost like it hits a boost cut or is blowing out the spark when it hits high boost and WOT.

This is because the Link will have a temperature MAP lockout. Once it goes over 100'C it should throw a CEL to tell you. And anything over 100'C the MAP limit will more than likely be alot lower.

[Guilt-Toy]

check the clutch on your engine fan.. it might not be spinning the fan fast enough.