I'm continuing trying to find the exact cause of my overheating problem without tossing more money into the problem and getting no results. I've had the S13 for over 2 months with no problems, until last weekend. Please keep in mind I've searched, checked FAQ, and have a slight grasp on where I need to look into, but that I'm looking into getting a better prospective on what I need to do to solve the problem without more unecessary money being spent.

So last Sunday night I was sitting in the Starbucks drive through on my way home. I notice no problems, as I'm always keeping my eye on things (a DSM will teach you to do that on a regular basis ). A few minutes after I leave the drive through, I notice my temp guage is up there.......quite up there........as in the second to last dot before the "H" on the temp gauge. Ofcourse I pull over immediately and let her cool down so I can observe the problem. First thing I notice is that the coolant is not bubbling over and no steam is present from loss of coolant, so there is a good sign. Second thing I check is under the oil cap for presence of water, none. Third, I check under the radiator cap. Oil in coolant, none. Coolant level still up in the radiator, check. Get under the car and check for leaks, none. After she cooled down a bit, I started it up with the radiator cap off to see if the coolant was circulating, and it was not. So at this point I think it's the thermostat or waterpump, even though I see no sign that coolant has came out of the holes on the pump.

Next day, I purchase a brand new Duralast waterpump and thermostat from Autozone and toss them in. I also removed the clutch fan and rewired the electric fan to run constantly (man, what a difference in power and RPM rise). I fill up with coolant, as well as burped and bled the system. I also kept the radiator cap open to see if I could see the coolant circulating, which I failed to see (even at normal operating temp). take her for a 5 minute spin.

She stayed cool for those 5 minutes, but shortly after, the temp once again gradually began to rise (I mean slowly, not skyrocketing in any sense). I get her back to the house before she reached a significantly high temp, parked her, and let her cool down. Started it back up with the cap off to see if I saw circulating, and I did not. I grabbed the radiator hoses to see if there was a significant temperature difference between the two. The upper was quite hot, while the lower was quite cooler (maybe luke warm at best). I also checked the pump and water neck areas to see if they were completely sealed, which they are.

So at this point, I'm thinking maybe it's a clogged radiator. Appearantly the problem is that coolant is not circulating through the system. My questions are:

- Is this a reasonable assumption given all the checks I have done and found to do?

- Would a radiator flush and system refill be the ideal thing to try next, or should I simply look into investing into a new radiator?

- Does the thermostat need to be completely flush and seated on where it needs to go to work properly? I found it somewhat tricky to get it to seat correctly without using a tad of RTV sealant to hold it to the waterneck.

- Should I ditch the Duralast thermostat for an OEM or other brand?

Any imput is appreciated.

 

the thermostat might be an issue... i would use a nissan one to be safe... but a simple test to check for flow would be to remove the thermostat and start the car... there should be plenty of flow now... if that is the case then the thermostat is at issue... if there is still limited flow then a radiator is needed...

 

I know on the pre-catalyst cars, I removed the thermostat. With these newer cars, I don't think you would want to or could remove it. I often felt, after owning a newer 240sx (1991) with the newer front end and my 1989 Hog Nose 240, which I now have, that, especially with air conditioning I feel that these cars have poor circulation through the front. However, mine never moves off of the 190 degree mark! So the front ends are not an issue. I have also notice that the on the early models that radiator corrosion on the front cooling fins have been a problem, especially if the car has a lot of miles on it, been where there is a lot of humidity, rain, salt, etc. I had this problem on my 1990 Mitsubishi GSX (2 of them) They have copper radiators and are old. After replacing it with a newer aluminum type, problems went away. I have had other guys on Columbus DSM which had the same problem you are describing. I would say that yours may be bad as well. May be!!! Don't bank on that. It sounds like you have done all of the checks I would have done and replaced the cheaper things first. Keep us informed and good luck.

 

I know it's a stupid question, but did you put the thermostat in backwards, perhaps?

 

As long as the top hat faces up, and the spring faces into the block, then no.

 

Spring down,you are correct. Just off the note, I have used aftermarket thermos before and have not had any problems. Maybe the head is cracked? If the cooling system has been maintained over the years, then rust should not be a problem. Try checking the spark plugs for a uniform color, just to rule out the possibility of coolant or oil being burnt inside of the combustion chamber due to a crack. I just don't know what else to tell you. Timing, maybe

 

temp sensor could be bad.

 

Would any of these, or a bad temp sensor cause the coolant not to circulate? Would a crack yield any hinder in performance or be noticable?

 

No. The temp sensor, I believe, tells the temp guage what to read. I forgot about that. The would be an easy fix. I don't know how much, though. Cheaper than a radiator. Just another note. Hard water, over time, can cause the radiator and head passages to gradually solidify and close shut (calcium) and other crap in water. I know a radiator shop can "Rod" them out, hot tank and clean like new. That's if you need a radiator. I don't know $$$. Look at the front of your radiator, especially at the bottom. Are there any of the fins missing or appear to be corroding? Brass will be greenish in color. I usually rub my hand across the fins. If the break or flake off, that's a good indicator of a failling radiator. The fins are vital in cooling an engine. But if you changed the engine and not the radiator, then I would check the radiator more closely. I lived in Japan for 10 years and know that the Japanese take care of their cars and their inspections are tough. But that doesen't mean that they don't baby them, especially the ones we are buying (performance type). They can beat on them pretty good. I assume that you didn't have this problem before the swap, did you?

 

No swap here. Stock '91 KADE.

 

I'm sorry. I thought your post said you had replaced the motor. I assumed it was an SR.

 

did you try removing the thermostat to find out if the radiator is plugged up yet??? there are only 3 things that can keep the system from flowing water... one is the pump... the other 2 are thermostat and the last one is a clog in either the radiator or the or somewhere in the cooling system...

easiest way to check is to remove the thermostat to see if you can get water flowing... if it flows then replace the thermostat again... if it dont then it is most likley the radiator since you put in a new pump...

 

Problem found. I will explain this for the next person with this problem.

What I did was remove the Duralast thermostat and flush the system with a bottle of Prestone flush solution without the thermostat in (which is the RIGHT way of going about it).

During the flush, and after the system is filled and burped and radiator cap is left off, you should notice a steady rush of coolant at any temp reading since the thermostat is not in (the current should be a strong current, especially with a newer waterpump). Well in my case, the flow was there, but VERY weak. If you barely turned your faucet on to a steady stream, that was the intensity the flow was (should be a strong, rushing current flowing through). Ontop of that, the classic sign of restricted flow is if you grab the radiator hoses for the heat disapation. They should both be pretty hot at normal operating temperature, with the lower hose being slightly cooler.

If the upper hose is hot, and the lower is cool or luke warm at best, you are looking at circulation problems. If the thermostat is out, the radiator is the problem.