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Jjtxaz24

1991 GT-R overheating

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What's going on guys? I have a 1991 GTR and just got it. Its currently overheating and when it does the oil temps get up there too.

I tried to search but didn't see the issue i was having. I have a theory on what it might be but I'm going to wait and chime in when you gurus reply.

Hint: thinking its the water pump because oil temp and coolant temp go up at the same time, meaning its not circulating as it should. Gets so hot it starts to boil.

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Well firstly, congrats on picking up the new car! 91 is an unusual year, was it Australian delivered?

As for the overheating, unfortunately there are a lot of potential reasons and not enough info to really guess.

If it overheats when stationary (unusual on these) it suggests some problem with the viscous coupling on the fan, these wear out but generally seize to be on all the time

If it overheats based on time or load when driving there are a lot of things to check and you may want a mechanic to do them

-air lock somewhere from coolant not being bled properly. rebleed the system including having the heater on full and opening the bleed on the intake manifold near the injectors, and using some sort of bleeding funnel. If the car had been serviced by someone who wasn't careful this is the most likely issue.

-thermostat not opening, this will make it overheat pretty quickly but is an easy fix

-leak in the system. run a pressure test and make sure there is no issue. another symptom here will be coolant loss. Leak could be in the radiator, hoses, heater core, radiator cap not holding pressure. Potentially and expensively but unlikely, it could also be a head gasket or block crack.

The water pump itself can't fail to pump as it is belt driven from the fan/water pump/alternator belt. That should be obvious if missing....when water pumps fail they leak from the seals

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Oil temp goes up because water cooling system isn't working properly. First I'd flush the system (take out radiator, flush that, then flush the block). Also check your clutch fan, it should spin with resistance (engine off), and you should hear it turn off after a bit when you first start the car cold, and engage (go loud) when it gets hot.

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Appreciate the help guys. 

Pulled out the thermostat and tested it. It appeared to be working, found a replacement at a parts store off a 95 300zx so minus well change that out since I was already in there. 

Next up is the clutch fan. I remember spinning it but it didn't seem to put up much resistance, trying to find one locally (I'm located in Texas) I looked around and read a 1991 Pathfinder clutch fan works. Do we know if this is accurate?

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Ahh that will make it a bit trickier.

Not sure about the pathfinder option, here we generally use rb30 skyline or patrol as the cheap but compatible replacement.  The good news is it only has to fit physically so if you take yours off you should be able to compare.

Did you flush it out thoroughly, rebleed everything properly and do a leak test? Chasing and changing parts is doing the hard things first.

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Good news guys, I was able to locate a 1995 300zx thermostat. Although it is a bit shorter from the top the rest of it is identical to the stock nissan one. Ill attach a picture just for a reference. 20190413_202729.thumb.jpg.f0b3b21148abe935035513a7219bf585.jpg

20190413_202656.thumb.jpg.b1700cd9a8e0e63a14c4bc248c6de124.jpg

When I pulled the old one out, it read Nissan on the top. So it may have never been changed, either way I needed a new one. 

Cleaned up the clutch fan as well with some WD-40 on the little coil part and a wire brush. That gave it back some resistance when I spin it. Used this video as a reference: 

 

Anywho, used the manual and refilled the coolant, and topped it off. Drove around for about 40 minutes with some spirited driving, freeway, and put myself in some stop and go. Temp stayed at halfway and my oil temp was good too. Im pretty sure its fixed.

Thank you guys for the help.

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1 hour ago, niZmO_Man said:

Probably just needed a good flush and bleed.

Yeah I think so too. Replaced the thermostat since i had already gone through the BS of taking the old one out. 

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If you are in Texas, may consider getting a new radiator if you are still running on factory one.  Both Koyo and Mishimoto offer reasonably priced replacements.

As for the fan clutch, if I recall Infiniti Q45's can work but not exact.  There was an discussion about interchangeability on Rivsu's old forum before they went out of business.  From what I can remember, almost all the late 80s and early 90s Nissan clutch fans share the same bolt pattern but vary a few mm in height, and unfortunately there is not one with the exact height as R32.

Edit:

Here is an old picture I found, not exactly sure which car this came from, could be a Z32.  So the unknown new fan clutch is the exact same height as R32, but somehow the base is 2mm thicker and so the nuts could not be tightened through all the threads.  

p0I5cOe.jpg 

Edited by TXSquirrel

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Did some driving around and its been a couple of days with no overheating. Drove it to work today and noticed this happening. 

I was parked here but I usually notice it at lights on stop n go traffic, etc...

What were looking at is when I press the brake in the needle in both gauges will rise, when i let it go they will drop. Do you guys know why that is?

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Looks like she's l running a bit hot (noting it may well have been a hot day there...)

That movement in the gauges must be a minor electrical issue.....either a bad (common) earth, or gauge power circuit, or even battery terminals. I haven't seen it before but I wouldn't be worried.  Does the volt gauge work (and, does it move when you put your foot on the brake?)

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2 hours ago, Duncan said:

Looks like she's l running a bit hot (noting it may well have been a hot day there...)

That movement in the gauges must be a minor electrical issue.....either a bad (common) earth, or gauge power circuit, or even battery terminals. I haven't seen it before but I wouldn't be worried.  Does the volt gauge work (and, does it move when you put your foot on the brake?)

Yeah its a little hotter today here than it has been. My volt meter does work and it reads just above 12 volts. It doesn't move when I press the break. 

I believe it when you say it might be a bad ground or wiring issue. Noticed it flinches very little with the blinkers on as well. Car needs a good scrubbing down in that engine bay and grounds redone. 

I have the ground (negative cable) from the engine to the negative battery terminal and about halfway to the battery is another grounding point (not grounded) Do you know where that goes too on the chassis?

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That is very likely to be the issue if the main battery earth is only connected to the engine.  It should go to the chassis first just near the battery (above hicas pump if you still have it), just an m6 thread that you put a bolt in. Let me know if you can't find it, I'll try and get a pic although my setup is a little non standard.

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BTW healthy alternator should be charging the battery at something around 13.8v so 12 is not right. Noting the standard gauge is hard to read properly.

If you have a multimeter check the voltage across the battery when the car is running.

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4 minutes ago, Duncan said:

BTW healthy alternator should be charging the battery at something around 13.8v so 12 is not right. Noting the standard gauge is hard to read properly.

If you have a multimeter check the voltage across the battery when the car is running.

Ill check the voltage when its running. Ill do that. Let me go look and see if i can see where the negative gets hooked up too. 

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