1991 GT-R overheating

[Jjtxaz24]

42 minutes ago, TXSquirrel said:

Hmmm sounds like you have all the basic maintenance covered.  I am sure you have checked them, but your fan, fan blades, and fan shrouds are all in good shape?  And you already replaced your water pump right?  

I notice your oil pressure is looking a bit low, but that could be because your oil was running so hot and viscosity decreased.  Mine sits at ~4 during idle.  Hopefully other can chime in on this, and hopefully that's not a sign for a bad oil pump.  (However, oil pressure sender is known to go bad, could be as simple as that.)

As for the radiator hoses, the lower hose is supposed to be cooler than upper hose.  (I have a laser thermometer that I can measure the delta next time I take my car out.)  But are you talking about a big temperature difference between the upper and lower or the lower not warm at all?  If so then I am drawing a blank since you already flush your radiator...

Like you said, maybe try another thermostat.  It's been around 85°F here and a healthy factory radiator should be able to cope with that.

Yeah the fan, fan blades and shroud are good. Very fee small cracks on the fan but nothing to affect performance or cause it to overheat. I did NOT replace the water pump. I was told that usually when those fail you'll know they either get broken inside, physically or leak from the gaskets because they are belt driven. 

I hope its not the oil pump, that means I'd have to pull the engine to do that. The oil pressure is sitting there after (in reference to the pictures) I drove it back and it over heated. Ill check later this week where it sits at idle, I'm sure its at the ~4 as well. 

Edit: checked my youtube link i posted in the thread earlier and it was sitting just a hair below 4 on my pressure gauge as it idled. 

Radiator hoses- I was talking about just during the flush. It advises to touch the lower hose and it should be running warm water as the "thermostat" should have opened. Then it instructs to race the engine at 2500 RPMS. I dont get that, so I just race the engine then it warms the coolant up on the lower hose and its good. 

I'm gonna try another thermostat. I really didnt want to take that housing off again and rebleed the system ha ha. 

Side note: is there oil filter relocation kits that AREN'T GREDDY and upwards of $200+

Edited April 23, 2019 by Jjtxaz24

[TXSquirrel]

2 hours ago, Jjtxaz24 said:

Side note: is there oil filter relocation kits that AREN'T GREDDY and upwards of $200+

I image a relocation kit for Z32 should work because oil filter is the same size.  Most kits out there offer only the oil filter adapters, and you will have to run your own oil lines.  I think you can even find oil filter adapters at local parts store and make your own kit, as long as the thread size is correct.

https://www.kseriesparts.com/BLO-BXGA-00115-PO.html

https://conceptzperformance.com/bde-remote-oil-filter-block-adapter-relocation-kit-nissan-300zx-z32-bde-rofr_p_34184.php

 

[Jjtxaz24]

Well its been a little while since i last posted and unfortunately I'm still overheating. 

Whats been done since my last post is:

Ordered a new radiator, mishimoto. It wasnt till i got it that i realized that i have a 50mm one and that doesnt allow me to leave the fan shroud on it like the smaller ones do (after i looked up why the fan shroud didnt fit with the radiator bolted into place)

Checked the thermostat again and it was opening. I have a mishimoto thermostat coming in thats supposed to open at 62° c rather than the stock 72°. I havent decided if i wanna change it or not.

My AC condensor was so old and brittle it was useless and well I currently didnt have AC so i pulled it for the time being to remove the clutter and allow more air flow.

Bought a radiator bleeding funnel looking thing. Worked good. Really felt like i got all the air out the system that way with it. 

Took the car on a test drive and oil pressure stayed under half and the coolant temp stayed normal. 

Drove it to work, around work all day and from work. Not a sign of overheating. I did notice i was leaking a bit of coolant, tightened my lower hose it looked like it was slipping off. Cross my fingers that it didn't get air in the system. Drove fine.

Got close to home and decided to rip it around the block till I can get the oil temp up over half, sure enough I did. Up went my temp again. Parked it to let it cool down and i noticed my radiator cap was barely on. Idk if I didn't put on all the way when I closed it or the pressure pushed it up. 

Im gonna try to rebleed it one more time but I honestly dont think thats my issue. Gonna order a test kit to see if im getting gases mixed into my coolant and possibly a blow headgasket.  Ot sure what else would cause it to overheat. 

In short: changed thermostat, bled system as manual instructs, still overheated.

Changed fan clutch, rebled system as manual states still overheated.

Rechecked thermostat, its working, resealed it, changed radiator to a new mishimoto, removed ac condensor, rebled using a radiator funnel, drove fine in tx heat to and from work. Only went up in temp once oil temp went up past half. 

Edited May 7, 2019 by Jjtxaz24
Added picture of radiator cap after inspected.

[Jjtxaz24]

[admS15]

Air would have been sucked back in to the cooling system from the loose lower hose and loose rad cap. Bleed it thoroughly and repeat test drive again before chasing anything else.

[Jjtxaz24]

1 hour ago, admS15 said:

Air would have been sucked back in to the cooling system from the loose lower hose and loose rad cap. Bleed it thoroughly and repeat test drive again before chasing anything else.

I bled it again but didnt drive it to work. Ill check it tonight.

Bled it by turning it on with the funnel in place, heater on, and block air bleeder removed. Fluid came out through it. Plugged it, let it warm up to operating temp with heat still on, revved it to force coolant flow then turned off heat, and closed it. 

Hope that does it. 

[Duncan]

Just want to check because you didn't mention specifically. The most important coolant bleed on the gtr is above the plenum next to the fuel rail. With that open and a funnel in place you should get nothing but coolant out the bleed.

[KiwiRS4T]

For an overheating car my first port of call is always the radiator.  Take it to a radiator specialist who can take the top and bottom tanks off and clean the thing properly and report if the core is stuffed. If its ok a new top tank is often called for - especially if its plastic. For a new radiator unless you are track racing I like stock the best. Same for radiator cap and thermostat. If you must get an aftermarket radiator make sure you can fit the stock fan and shroud as otherwise you will lose a lot of cooling. '

FWIW I have heard bad things about Mishimoto radiators and  their caps.

If you are 100% sure of these basics including the block flush and proper bleeding (all of which need doing from time to time anyway on an old car) and you are still overheating then none of this effort is wasted and you can look elsewhere for problems. Also check your engine when it is at max temps with a laser thermometer to make sure it really is hot and its not your gauges that are at fault.

Have you checked the oil for water and vice versa? Observe the radiator with the cap off for evidence of bubbling when you give it a rev? Pulling the plugs will give you some clues and also a chance to do a compression test.

[Jjtxaz24]

6 hours ago, Duncan said:

Just want to check because you didn't mention specifically. The most important coolant bleed on the gtr is above the plenum next to the fuel rail. With that open and a funnel in place you should get nothing but coolant out the bleed.

Correct. Opened the bleeder by the valve cover. Funnel in radiator and turned it on. Pushed out fluid and I capped it to ensure no air got back in.

3 hours ago, KiwiRS4T said:

For an overheating car my first port of call is always the radiator.  Take it to a radiator specialist who can take the top and bottom tanks off and clean the thing properly and report if the core is stuffed. If its ok a new top tank is often called for - especially if its plastic. For a new radiator unless you are track racing I like stock the best. Same for radiator cap and thermostat. If you must get an aftermarket radiator make sure you can fit the stock fan and shroud as otherwise you will lose a lot of cooling. '

FWIW I have heard bad things about Mishimoto radiators and  their caps.

If you are 100% sure of these basics including the block flush and proper bleeding (all of which need doing from time to time anyway on an old car) and you are still overheating then none of this effort is wasted and you can look elsewhere for problems. Also check your engine when it is at max temps with a laser thermometer to make sure it really is hot and its not your gauges that are at fault.

Have you checked the oil for water and vice versa? Observe the radiator with the cap off for evidence of bubbling when you give it a rev? Pulling the plugs will give you some clues and also a chance to do a compression test.

Your saying the brand new aliminum radiator I just swapped in for the 28+ year old stock plastic one still needs to get pressure tested??? I've heard nothing but good things about Mishimoto. 

The stock fan shroud did not fit on the nee radiator. I did remove the ac condenser and bumper is still off. I dont believe its not an airflow issue due to the fact that it would overheat at lights and stop n go traffic it doesnt. It overheats when my oil temp gets over half way and ive been beating on it. 

Ill get a laser thermometer to check the temp when its hot. See what its really at. 

I have checked my oil and there is no signs of coolant in the oil, or it looking milky. 

[TXSquirrel]

Not having fan shroud on there with your new Mishimoto can be an issue, and that could be why it overheated at lights - the fan not pulling enough air through radiator.  I think the shrouds are the last piece of puzzle, you should get good cooling improvement if you can somehow fit them back on...  (I am surprised though because with my 48mm Koyo both upper and lower stock shrouds fit.)

How are your plugs looking?  Just want to know if it's running lean...  Also do you have a picture of your engine bay?  

[Jjtxaz24]

2 hours ago, TXSquirrel said:

Not having fan shroud on there with your new Mishimoto can be an issue, and that could be why it overheated at lights - the fan not pulling enough air through radiator.  I think the shrouds are the last piece of puzzle, you should get good cooling improvement if you can somehow fit them back on...  (I am surprised though because with my 48mm Koyo both upper and lower stock shrouds fit.)

How are your plugs looking?  Just want to know if it's running lean...  Also do you have a picture of your engine bay?  

I am NOT having issue with cooling at the lights. I do agree that i need to fix the shroud on there  I think this radiator may be a bit shorter than my stock so i need to find/make a way to raise it so it clears the fan with the shroud on. 

》》》My current issue with it is if i drive it hard, my oil temps will creep up to the midway point. Once they do and if I'm still driving hard itll spike my coolant temp. Once I see that and if I let it cool down and let my oil temp drop under mid way, coolant drops and I'm good to go. 《《《

After being properly bled. If I cruise and drive it normal from the get go, there is no issue with my oil temp, it stays below half and my engine coolant temp reads just below half as well. Ill be able to drive it all day and its been in the 90° F here in Texas.

Haven't checked the plugs yet currently at work and I dont have a current picture with the nee radiator in, ill get one today and post it up for you guys to see. 

Apologies for the confusion and thank you for your help. I appreciate it. 

[niZmO_Man]

Umm that's because your coolant/water heats up as the engine/oil heats up. On the track my car would hit 130degC before the normalised temp gauge shot up past half/mid.

If you're using your standard water temperature gauge, remember it's normalised (sits at mid even though there's change in temps).

[KiwiRS4T]

9 hours ago, Jjtxaz24 said:

 

Your saying the brand new aliminum radiator I just swapped in for the 28+ year old stock plastic one still needs to get pressure tested??? I've heard nothing but good things about Mishimoto. 

 

I didn't say that. I said if you pull your plugs out that will give you a clue as to what is going on and also the opportunity to do a compression test on the engine.

[Jjtxaz24]

Ok so yesterday i bled the system. The whole 9. Didnt get to drive it. Today i got around to driving it. 

Here's what it looked like after driving it hard for a bit. Once i saw it hit that temp in the oil i let off and cruised around. I did swap my broken mishimoto radiator cap for my old stock one. Its rated for a lower pressure than the mishimoto.  

 

Also heres a pic of the engine bay someone asked for. 

The mishimoto is about an inch and some shorter than the stock and that is why the shroud dont fit. Ill be making something to raise it up to stock height and put the shroud on when I do.

You can see i removed the ac condensor, was gonna wire up the condensor fan to a stand alone switch just havent gotten around to it. 

[KiwiRS4T]

Does the oil get any hotter? That's just over 100 which is not exactly panic stations. A good synthetic will stand 120 Deg C (which is too hot for comfort).

If it keeps on rising from there (as per your pic) you have got a problem. Can you get your AFRs checked to see if you are running lean for some reason? Or you might be able to discern that from the condition of the plugs.

[Jjtxaz24]

6 hours ago, KiwiRS4T said:

Does the oil get any hotter? That's just over 100 which is not exactly panic stations. A good synthetic will stand 120 Deg C (which is too hot for comfort).

If it keeps on rising from there (as per your pic) you have got a problem. Can you get your AFRs checked to see if you are running lean for some reason? Or you might be able to discern that from the condition of the plugs.

Yeah, before when the overheating issues were worse it would spike pretty high and cause my coolant temp to spike as well and I'd park it and let cool down. Coolant would be boiling and eventually it would overflow my coolant overflow tank and spill out. 

I checked the plugs when I first got the car and I havent since. I can pull em again and see if they're good. Might just change em since that's an easy fix. 

I don't have a way to measure the AFR. It's on my "to get list", along with a CV boot for my driver side outer side (any cross over cars that fit our CV Joint). 

[TXSquirrel]

You pick the wrong boot to break lol.  I believe inner boot is shared by a bunch of Nissan or Infiniti models, less so for outer boot.  But you can still find them everywhere:

https://www.ebay.com/itm/Nissan-C9BDA-05U8H-OEM-CV-Boot-Repair-Kit-Front-Outer-RB26DETT-R32-R33-Skyline/202543719660