KA24DE overheating, can you figure it out?

[OverBoost]

First of all, yes I have searched, but I have a unique situation. I have a '91 KA24DE, completely stock except for a Mishimoto aluminum radiator. The engine has just been rebuilt, every part of the cooling system is new: waterpump, 170 degree t-stat, temperature sensor, hoses, rad cap, circuit sports aluminum overflow tank. I am running Dual Altima fans at high speed on a temp controlled relay.

Problem: the engine keeps overheating after the car warms up and drives around for about 10 minutes. The outside temperature doesn't matter, even though I live in South Carolina. When it overheats, the temp needle gets almost all the way to the top and the coolant overflow bubbles over. The upper hose will get VERY hot (as in burning to the touch) and the hose visually expands (due to the pressure), but the lower hose remains cool to the touch, including the t-stat housing.

I have bled the system numerous times, jacked up the front, there are no air bubbles in the system.

My theory: the aluminum radiator is doing such a good job at cooling, that the t-stat wont open because the incoming water is below 170 degrees.

Can anyone add their thoughts or theories as to why my car keeps overheating? I want some of your input before I go out and spend $70 on a Nismo 144 degree t-stat.

Thanks guys!

[fail wagon]

headgasket?

[M11's]

obviously if it is overheating and burns to the touch it is hotter than 170. If the lower rad. hose is remaining cold you may have put thermostat in wrong and its not opening to circulate coolant, so its putting pressure on upper hose and pouring out.

[Forge_55b]

Run no thermostat and see what happens.

[negrosx13]

^^dont run the t-stat but that doesnt really fix your problem

[Forge_55b]

taking it off lets you know if that was the problem or not

[mxexux]

test the t-stat in a pot full of water and a thermometer over the stove. I do this when replacing the t-stat because its easy and you would be surprised how many new t-stats get stuck closed.

[nismo91blk240sx]

Originally Posted by M11's

obviously if it is overheating and burns to the touch it is hotter than 170. If the lower rad. hose is remaining cold you may have put thermostat in wrong and its not opening to circulate coolant, so its putting pressure on upper hose and pouring out.

im having the same exact problem with the overheating

is there a certain way to position it in the t-stat housing?

pics?

[Fam0uZ]

take the t-stat off and see what happens....

[jholman05]

I would take bets the system is still not blead correctly. Also the t-stat does have a certain way of going in, there is a little "breather" that needs to be on the top, I'm guessing this allows air bubbles to go through it. I always park mine on a hill, open the bleeder on the intake manifold, take the rad cap off and let it idle for like 30 minutes, keeping an eye on the bleeder to make sure nothing is coming out. Also I turn the heat on, IIRC there is a valve on the heater core that lets warm coolant in when the hvac switch is on heat. You could have some air in the heater core... I used to have the problem with overheating like you did the first couple times I drained the system.

[Phlip]

When this happened to me a couple years ago, it was the head gasket.
Fully bleed the system, try again and if the problem persists, pressure test the system.

[stunnaben]

I'd say running it while it over heats is gonna cause you to blow a head gasket, I know i did.... once you do that, shit gets super hot super fast. I'd check that out and I'd look into bleeding the system. KA's are notorious for wanting to over heat. I have a mishimoto as well. Great radiator but you gotta bleed it correctly.

[CrimsonRockett]

My buddy's car was overheating after installing a Mishimoto radiator.

Bled the system several times with no luck.

The radiator cap was actually to blame. Mishimoto radiator caps are notorious for this.

Swapped it out for an OEM one and problem went away.

Might not be the solution to your problem, but it's worth a try.

[DALAZ_68]

Originally Posted by CrimsonRockett

My buddy's car was overheating after installing a Mishimoto radiator.

Bled the system several times with no luck.

The radiator cap was actually to blame. Mishimoto radiator caps are notorious for this.

Swapped it out for an OEM one and problem went away.

Might not be the solution to your problem, but it's worth a try.

agree...it would also be a perfect time to upgrade to a pressure release valve radiator cap...

[OverBoost]

Thanks guys for all the input.

I have tested the t-stat in boiling water and it does open at 170 just as it should. I know the t-stat is in the correct way (spring-side in), it will only go in one way, otherwise it falls off when you try to put on the t-stat housing.

I have bled it numerous times, before and after taking the t-stat out to test. I raised the front end, ran the car for 15-20 minutes, heat on full blast, funnel in the radiator neck with fluid in it for bubbles to come up in. All bubbles did seem to evacuate, but I did not do it with the intake manifold bleeder off. When I was bleeding it the latest time, the car did stay at normal temp, but when I took it out on the road the temp did go up, but not all the way.

While it could be the radiator cap, I have tried the stock Mishimoto one and a Stant rad cap, both seem to be holding on pretty tight and are new units.

I may try it without the t-stat to see if that makes a difference, but it will take a lot longer for the engine to get up to operating temperature.

Anything else I should try?

[mxexux]

Check if your fans are spinning the right way. If they are spinning backwards the car will overheat only while driving. Maybe the polarity was reversed when they were wired in.

[Azrial]

Originally Posted by OverBoost

Thanks guys for all the input.

I have tested the t-stat in boiling water and it does open at 170 just as it should. I know the t-stat is in the correct way (spring-side in), it will only go in one way, otherwise it falls off when you try to put on the t-stat housing.

You can have it in the right way but have upside down. Make sure the nub is at the top. Also are you sure you wired your dual fans the right way. They could be blowing instead of pulling air.

[OverBoost]

I'm not 100% sure about the t-stat being installed with the "nub" on top, I will have to pull that off and check. The FSM says nothing about that, thus why I thought it wasnt a big deal.

The fan are absolutely blowing the right way. You can feel the suction on the front AC condensor before the radiator, ie: put a piece of paper/leaf in the bumper inlet and it will suck it towards the engine. They cool the engine down properly when the engine is off and key in ACC position.

[s142jzkillav10]

Sounds like you have a HeadGasket issue. This happend to a friends old KaDE with 190K

[ZCrazy93]

To be honest it sound like vapor lock due to air in the system. However, I say try the no T-Stat approach first and bleed again. This will tell you If it is locking up due to air in the system. If it cools and doesn't heat up you know you were locking up the T-Stat with air (provided it works properly). If it still overheats there is something wrong internally, eg. water pump, block/head. Also is it burning coolant out the exhaust, thats a sign of a head gasket issue? Does the temp react to different throttle positions/rpms, that could be a sign of pump issues? The fact that it is not circulating coolant leads me to believe it is something with the T-Stat or air in the system. If it builds pressure in to the radiator, the pump is pumping and the cap is more than likely working ok so that only leaves the T-Stat, radiator and block to be a problem. A sign of air in the system is cold air out of the heater system when the temps are normal/high. To test that the radiator didn't break or get restricted disconnect the upper and lower hoses from the engine and blow water through it with a hose, if you find restriction you'll know. (Becareful with pure water through the system for any length of time because pure water can rust a system if left in there long enough.)

Check some of these things and report if you haven't found the problem yet.

[Dream240]

Originally Posted by OverBoost

I'm not 100% sure about the t-stat being installed with the "nub" on top, I will have to pull that off and check. The FSM says nothing about that, thus why I thought it wasnt a big deal.

Unfortunately the 91-94 FSM didn't have the extra note that the 95-98 FSM did regarding the thermo valve. See attachement.

So yes it is relevant. Check that and then re-bleed the system. Basically, if you're lower hose is not getting hot then your thermo is not opening properly, plain and simple.

[Fred Allen Burge]

I've had overheating issues on almost every KA I've ever had to drain and refill. It's ALWAYSSSSSSSSSSSSSSSSSS been air in the system. ALWAYS!

I didn't see where you said anything about bleeding the heater core.....you must bleed the heater core.

There's a thread around here on how to do it, it involves taking off the upper heater core hose at the firewall while filling up the rad. That forces the air out of the core. Seriously, the KA core design is a biotch, I read somewhere it has to do with the fact that the car was designed to be RHD originally, not sure.

If that works for you and you feel grateful, feel free to say thanks using the button below:

[wow-thats-a-cool-car]

Originally Posted by Fred Allen Burge

I've had overheating issues on almost every KA I've ever had to drain and refill. It's ALWAYSSSSSSSSSSSSSSSSSS been air in the system. ALWAYS!

I didn't see where you said anything about bleeding the heater core.....you must bleed the heater core.

There's a thread around here on how to do it, it involves taking off the upper heater core hose at the firewall while filling up the rad. That forces the air out of the core. Seriously, the KA core design is a biotch, I read somewhere it has to do with the fact that the car was designed to be RHD originally, not sure.

If that works for you and you feel grateful, feel free to say thanks using the button below:

Are you fucking serous? you want someone to pay you for giving them you 2 cents? Your an idiot! GTFO

And this thread has been super useful...i'm having the same problem

[Dream240]

Originally Posted by Fred Allen Burge

I've had overheating issues on almost every KA I've ever had to drain and refill. It's ALWAYSSSSSSSSSSSSSSSSSS been air in the system. ALWAYS!

I didn't see where you said anything about bleeding the heater core.....you must bleed the heater core.

There's a thread around here on how to do it, it involves taking off the upper heater core hose at the firewall while filling up the rad. That forces the air out of the core. Seriously, the KA core design is a biotch, I read somewhere it has to do with the fact that the car was designed to be RHD originally, not sure.

If that works for you and you feel grateful, feel free to say thanks using the button below:

That's strange, since I've NEVER had to bleed to cooling system from anywhere but the radiator. I'm on my 6th 240, and never had this problem or had to bleed the heater core that way. That's just crazy talk.

As far as my experiences go, you should allow the car to warm up with the heater on full blast. This will allow any air trapped in there to travel towards the lower hose and wait to be expelled. I think this is even mentioned in the FSM. If your car isn't doing this, then you might have some more serious problems with your car like clogged/rusted cooling ducts, a bad heater core, or failing water pump.

[Fred Allen Burge]

Originally Posted by Dream240

That's strange, since I've NEVER had to bleed to cooling system from anywhere but the radiator. I'm on my 6th 240, and never had this problem or had to bleed the heater core that way. That's just crazy talk.

As far as my experiences go, you should allow the car to warm up with the heater on full blast. This will allow any air trapped in there to travel towards the lower hose and wait to be expelled. I think this is even mentioned in the FSM. If your car isn't doing this, then you might have some more serious problems with your car like clogged/rusted cooling ducts, a bad heater core, or failing water pump.

Well, he's already bled it at the radiator, I don't think he screwed that process up so...

Instead of doing what I said you feel that he should:

1. Go and screw around cleaning water ducts
2. Diagnose for a bad heater core
3. And/or replace his water pump


Wow.

(@OP - just try what I said first)

[Fred Allen Burge]

Originally Posted by wow-thats-a-cool-car

Are you fucking serous? you want someone to pay you for giving them you 2 cents? Your an idiot! GTFO

No, I'm not #$%^&* serious, we're YOU???

[Dream240]

Originally Posted by Fred Allen Burge

Well, he's already bled it at the radiator, I don't think he screwed that process up so...

Instead of doing what I said you feel that he should:

1. Go and screw around cleaning water ducts
2. Diagnose for a bad heater core
3. And/or replace his water pump


Wow.

(@OP - just try what I said first)

Yeah, wow.

Okay so you want him to disconnect his heater at the firewall and do what exactly, try and fill the core up with fluid and assume that there won't be any air stuck in there because he fills it until it pours out of the hose? Yeah great plan. Because there's no way air get's trapped inside something that is sitting in a static position...... sure. Maybe if he fills it up, holds the hose so that the fluid doesn't just pour back out, and then have someone jump up and down on the front bumper to jiggle any air bubbles out of there.

Well I don't know about you but I would stick with the FSM and tried and true methods for bleeding air out of the system.

Also, as far as my suggestions, they are the next typical things to consider when you have the bled the system properly and it's still overheating.

1. Poor coolant circulation due to corrosion and blockage.
2. Heater core is worn out, corroded, etc. and not able to properly evacuate the trapped air.
3. Water pump is not operating within acceptable parameters. Most likely needing replacement.

These things are not uncommon factors on a 15+ year old car that has had numerous owners with varying levels of maintenance. Some common sense will lead to alternative diagnosing procedures if it's obvious the bleeding process is not working the way it should. Hate to tell you but sometimes you have to actually use your brain when working on old cars, not just a set of wrenches and screwdrivers.

On a positive note, your posts sure are snarky.

[Big_Balls_JC_S13]

Well ive noticed this on my S13 my heater core was bypassed before I bought so i decided to hook the hoses back up. Ran in to the same issue of overheating so I say HEATER CORE FTW!!!

[jmac636]

Fact #1 -Heater cores are usually bypassed because they start leaking.
Fact#2 - Ka's are bitch to bleed the coolant system.
I just rebuilt my Ka-t and also installed an aftermarket radiator on another Ka and yes bleeding air is most likely the problem. Just run the car and keep filling the radiator with coolant with the upper intake bleeder open and squeeze the upper hose to blurp the air out. You can also feel the bottom hose to feel the temperture difference. Close the system add coolant to the resorvoir. Run it till it gets a little warm then let it cool and add more water. Also under the exhaust manifold is another bleeder for the block but I have never had to use it to fully bleed the system. Good luck!

[yukon]

Originally Posted by jmac636

Fact #1 -Heater cores are usually bypassed because they start leaking.
Fact#2 - Ka's are bitch to bleed the coolant system.
I just rebuilt my Ka-t and also installed an aftermarket radiator on another Ka and yes bleeding air is most likely the problem. Just run the car and keep filling the radiator with coolant with the upper intake bleeder open and squeeze the upper hose to blurp the air out. You can also feel the bottom hose to feel the temperture difference. Close the system add coolant to the resorvoir. Run it till it gets a little warm then let it cool and add more water. Also under the exhaust manifold is another bleeder for the block but I have never had to use it to fully bleed the system. Good luck!

The so called bleeder under exhaust manifold is the drain plug. Pour the coolant in slowly to allow air to escape. Most people dont have problems with air on 240sx's. Feeling bottom hose doesnt really tell you anything.