Overheating RB26 saga, more info, help!

[underground]

Fixed....

[meggala]

oil in coolant tells me head gasket

[sweetr33]

black oil in coolant is lookin scary(headgasket), But overheating would occur if the water was being sucked into the cylinders and being drained so to speak so no water is left in the cooling system. To me it sounds like the thermostat. If it overheats whilst ur cruising along(over 40kph) then u can rule out the fan/s. Does it overheat whilst idling and the fan going? Did u retain some sort of air conditioning system?

Sometimes running a car without a thermostat at all can cause it to overheat aswell as the water/coolant is flowing to quickly for heat tranfer to occur. But in other cases it works fine. I would be replacing the thermostat as ur first bet. Check water pump belt tension also, sometimes if the belt is not gripping the pulley then obviously the waterpump cannot circulate the water fast enough.

A number of other not so thought about things can cause overheating

*dragging brakes

*timing problem

*fuel mixture to lean

*and other things

Are u still running stock ecu or aftermarket?

Ample air flow to radiator(only an issue if it doesnt overheat whilst idling with the fan/s on)

[RBsileighty]

What's the temp/humidity been like around your area? AZ isn't exactly a cold state... sure it's not helping what could be a small problem. As far as what's in your overflow... has it done that since the coolant flush? I would imagine whatever solvent was run through pulled out what could be in the lines. If it's not doing that anymore then start looking at the small things first.

If you run the fan (HVAC) pulling air from the outside... when overheating do you smell the coolant burning? I had a leak from a water feed line to the turbo with a bad crush washer... no more overheating after that was fixed. A line leak is a lot easier/cheaper to fix than a headgasket. Might as well run a coolant system pressure test to see if you have any leaks. I don't know how old your motor is, but did you replace all of your hoses? Mine's a 93, so I went through and replaced all of the rubber coolant lines since over half were dry-rotted. Granted... I'm sure if this was your problem you would have noticed a puddle under the car. Wouldn't hurt to do a coolant system pressure test anyway...

Some background... what did you replace and what has been left alone?

Also... what gauge are you using to monitor your temp? I think I've seen that you are using an autometer unit correct? What thermocouple are you using? If the motor itself seems fine... it might just be your gauge/sending unit...

Good luck, and I hope this helps!

[Sydneykid]

The first thing I would do is get a pressure test done on the coolant system including the radiator cap. Any good workshop will have the necessary equipment.

[underground]

Update:

First, I found a water leak today that I believe has been part of the overheating problem.. Right where the lower radiator hose connects to the spicket, I had a nice flow of water when the motor was running...

I simply tightened down that clamp, (which was very loose) and that leak appears to be fixed.

I think the little bit of oil that was in the coolant was probably from the motor simply sitting... I don't think I have a headgasket issue...

I drained my engine oil and there was by no means any signs of coolant in the oil. None...No smell of coolant, etc..

Tonight we backflushed the motor, and got out quite abit of crud...

This should have been done three weeks ago when the motor swap was done, but the shop that did the work never did it..

I pulled out the Nismo thermostat (still out, drove the car tonight without it to test the temps) before I flushed the motor to ensure nothing would be left behind...

I drove the car without the thermostat tonight for almost two hours.. Temp stayed at 99 degrees celsius and didn't fluctuate.. this is an improvement.

Once I pulled off the interstate and was iding in traffic, the temps jumped to about 105 celsius...

While this is still not what I was hoping for, we are doing better than the 115 degrees celsius it was going to yesterday... and would continue to go past if I didn't turn off the car.

Im going to do the pressure test you guys mentioned..

Any other ideas?

Also, I have this one air leak that is driving me nuts. It's loud and noticeable, but I can't figure out where its coming from...

What should my vacuum be at idle? It's reading like 15 PSI of vacuum at idle.. which is about 850 RPM...

Chris

[underground]

To answer a few of your questions above, the motor is stock... Stock ECU, stock turbo's, etc..

No A/C, that has been pulled for weight reduction...

If anything the motor is running extremely rich... Kills my nose just to smell it...

The shop that did the work changed all hoses (as far as I'm aware).

[underground]

I'm using an Autometer Electric Temp Gauge... I have it tapped into the neck that the upper radiator hose bolts too...

I should also mention I have a oil leak with one of my turbos'.. The shop that did the swap told me that its coming from one of the lines.. He said I just need to reseal it....Maybe this is another issue, which might explain where the oil was coming from, if there really is an oil in coolant issue..

[sweetr33]

sheesh thats still running hot. seems strange, what heat range is that nismo thermostat? It runs hotter with the thermostat in? Does the engine stutter for a moment when u first start it after its been sitting for awhile? almost like its missing but then comes good seconds later? check all hoses for kinks or harsh bends.

[Cubes]

Is it spitting water out of the overflow?

[underground]

Is it spitting water out of the overflow?

It was originally. But now, that I have pulled out the thermostat and fixed that hose leak, it just sucks up water from the overflow if needed. No more spitting that I can tell....

[sweetr33]

maybe the cap cant hold enough pressure in the system and the waterpump is cavitating?

[underground]

sheesh thats still running hot. seems strange, what heat range is that nismo thermostat? It runs hotter with the thermostat in? Does the engine stutter for a moment when u first start it after its been sitting for awhile? almost like its missing but then comes good seconds later? check all hoses for kinks or harsh bends.

I believe the Nismo thermostat opens at 72-75 degrees celsius..

With the thermostat in, it would have boiled til the motor blew if I would have let it..

But, at the same time, I had that leak that I talked about.. After I tightened that hose down, my temps dropped and held consistent at around 99 degrees celsius..so, it could have been that hose that was causing the problems and not the thermostat...

Hot, but no longer rising endlessly..

As far as the stutter when trying to start, I don't notice anything like that...

However, there have been two different occasions in the past week, where it felt like my fuel pump had gone out for a second, and it kind of kicked the car forward when driving... Like it had a loss of power, but then it was find.. Only lasted for a few seconds..

I checked my sparkplugs they are the PFR 7A11s, and they are gapped to 0.40 I believe... I guess that's stock gap...

[underground]

maybe the cap cant hold enough pressure in the system and the waterpump is cavitating?

It currently has a 16 lb cap.... I will go and buy another cap today, and try that...

Also, I want to stick another thermostat in the motor...

We don't have Skylines here in the states.. I have been told that the GTR uses the same thermostat as a 91-96 Nissan 300ZX (Fairlady Z) TT....

Could anybody cross reference this part and tell me what other Nissan makes share this thermostat?

[Cubes]

Its not the cap.. I can drive around with mine clicked off so it doesn't hold pressure on a 40degree C day(I blew a hose and had to get home). Just have to make sure it doesn't suck in any air as to create an airlock which in turn boils the water turns it to steam creates more hotspots boils more and eventually blowing out the rest of the water and overheating the motor

Check your clutch fan and make damn sure the system has had all the air removed.

I use a 2ltr coke bottle. Chop the bottom off and use a rubber hose around the end which fits perfectly in to the top of the radiator.. Raise the water level above the highest point of the motor and keep it there. Run the motor with the heater on.

Crack the bleed nipples on both the top of the plenum (not sure where it is on the GTR's) and heater hose bleed nipples.

I have a FMIC and when my clutch fan wasn't working properly It was still getting hot even at 80-100km/h on a hot day.

[underground]

Clutch fan?

You mean factory fans?

If so, mine has electric aftermarket fans... No room for original fans...as I have a motor swap into my 200SX (Silvia, 240SX (US))

[Cubes]

Have you set the aftermarket fans up with a shroud and not bolted them directly to the radiator?

I had 2 x 12" crag davis thermo's bolted directly to my radiator.. They didn't cool enough. it was overheating slowly on a day over 35degree's C.

I put a new clutch fan on (the old one was stuffed hence the reason for going elec thermos) and the car can idle and be thrashed in 45degree heat forever and a day without the needle moving anymore than half a needle width.

The clutch fan is the stock fan yes.. its two parts.. the fan then the clutch.

[underground]

Yes, the fans have a shroud...

[sweetr33]

hmm interesting, i dont know about gtr plug gaps but i wouldnt imagin they would be as small as .4 standard. i was thinking more like .8-1.0 standard.

[R31 POWER]

Clutch fan?

You mean factory fans?

If so, mine has electric aftermarket fans... No room for original fans

That has to be it ay?I've heard nothing but bad from electric fans in place of the clutch ones!!