S13 Overheating only when I use the heater????

[theman4444]

1990 s13 with a rebuilt DE swap about 4000 miles ago. It runs extremely well. When we rebuilt it we changed out the thermostat and waterpump, and had the whole block acid dipped to take out any deposits. I haven't had a problem overheating until just a couple weeks ago.

So I've bled the dang car's coolant system about 5 times now. Every time it still over heats... It really sucks cuz I have to do it in the SNOW now...

It seemed to work totally fine after I bleed it IF I don't use the heater... I know what your thinking and YES I have bled the system while the heater was on full blast. Until all the air was out of it. So I don't THINK this is the prob.

Anybody guess what the problem is??? Maybe a bad thermostat? I don't think the water pump is bad. Maybe a clogged heater core? I really don't think it's a problem with air flow because I checked the fan clutch and it hardly spins before stopping so I think that's good. I think it's a prob with coolant flow somewhere......
Modified by theman4444 at 6:19 PM 12/1/2006

[180fan]

yeah it's possible that your heater core has clog or it could be yet more air trapped in the system.

reason for my thoughts on the matter to be the above case, if your heater were closed, it's pretty much out of the loop anyway, and if your car has overheated without the heater, then I'd point to other parts of the cooling system, but from what you make it sound like, as long as the heater core is in the loop then you overheat. I'd start snooping around there.

[theman4444]

So, last night it over heated again... after turning it on and it working fine for 3 miles of normal operating temperatures. I didn't use the heater the entire time, so I guess it will still over heat without using the heater....

But here's the wierd thing, I bled the system while on the side of the road (as best I could) with the extra coolant I had and a wrench. Then less than a mile down the road it started overheating again...

So my friend said he was having the same trouble said that turning the car off and then on while coasting will fix it temporarily. I did it and LOW AND BEHOLD the car went back down to normal temps for the rest of the 3 miles home....

I don't know what to do now, but I'm going to change out the thermostat and bleed the system one last time.

[theman4444]

Alrighty then, So I replaced the thermostat with a known working one and guess what? It still overheats.

I then checked the "old" thermostat and it works fine. So that couldn't have been the problem.

I really don't know what could be letting the air into the system.

It can only be two things right? Either a leak or I have a warped head. But my oil looks great so I don't think the head is warped.

I DON'T KNOW WHAT TO DO ANYMORE...

Someone Please help me.

[Defiant]

You don't have the thermostat in backward, do you?

[sliders]

could be bad coolant temp sensor ,could be faulty gauge,is it boiling over when you say its overheating or is the gauge just going up, did you put the thermostat in the right way. Check the temp with a infared gun when it is overheating and see what the temp is at the thermostat housing and around the head were the coolant passages are. Let us know.

[sliders]

do a block test to make sure you didnt blow a head gasket

[IDriveFords]

radiator could be clogged? This is probably a really stupid question but are you filling it from the radiator cap? You'll never get it right if you try and fill it from the overflow tank. Not trying to insult your mechanical intelligence or anything becuz I made this mistake on my first car years ago and could never get it to cool right until I reflushed it from the radiator cap. You also gotta burp the system by letting it idle with the heat on full blast and the radiator cap off to get out all the air pockets. Air pockets cause heat spots and overheating. The only other thing I can think of is if you had a clog somewhere, alot of times your radiator will clog and when your tstat opens you don't get a fresh flow. Also check your mixture unless your buying the premixed stuff. You could try to dump some redline water wetter in and see if this doesn't help cool it off. Is the temp just shooting up from normal to extremely hot instantaneously? Because usually when a car overheats the temps will gradually climb but if your getting an instant heat wave I'd question whether or not the gauge is reading correctly as well as if the coolant temp sensor is working right (they commonly go bad). Usually cranking up the heat will cause the overheating to settle at least a little.

[theman4444]

no I don't have the thermostat in backwards. I had a friend help me do it too.

I know for a fact that it is actually overheating as evidence by the boiling-over overflow tank, dumping my coolant on the ground. And the gauge is totally correct because it will slowly go up after about a mile not instantaneously. After bleeding it the temp gauge goes down again.

I am refilling it from the radiator cap when I bleed the system, and I loosen the bleeder cap on the engine to let any air escape. I do this either for 20 min after it is warmed up AND/OR I bleed it several times while turning off the car to let it cool again to let the bubbles move through the system before I turn it on again. Every time I always turn on the heat to full blast, which is 3 because the blower doesn't work on 4. I've tried doing it on an incline and on jack stands. I really don't think my technique is the problem.

do a block test to make sure you didnt blow a head gasket

Are you talking about a compression test of the cylinders or is this something completely different? But, no I haven't tried any pressure tests yet of the block or cylinders, or cooling system. I don't have a lot of money and I want to rule out other things before I bring it to the shop. If I have to, I will though.

I don't know if my radiator or heater core is clogged as I've not had time to really test these.

thanks guys, I still think it's a clog somewhere other than the block, like in the heater or possibly the radiator. How would you check to see if they are clogged? It's definitely not leaking on the ground. I really hope that it's not a head gasket. How do you test the head gasket??

[ricebike]

how's the cap? u can get a tester from autozone to check if it's still holding 13psi...

[theman4444]

how's the cap? u can get a tester from autozone to check if it's still holding 13psi...

Ok, so I bought a brand NEW radiator cap, and I totally flushed the system.

Water was easily flowing through the block and heater core. I also took off the radiator cap and took out the radiator drain-plug and water was easily flowing through both sides of the radiator.

I took it for a drive today to go to work and i does like it always does. It works fine and heats up to normal temps and even works fine in normal temps for like another 2 miles. Then the temp gauge starts to edge up and coolant starts to boil out of the overflow.

I really don't know what to do...

I've already ruled out thermostat and radiator cap. I don't think it could be the waterpump because it's new and it works fine for a long time down the road. I don't think there's a clog because it seems to flow water out of the system fine. It doesn't leak on the ground...

What else could it be but a warped head??? I'm running out of solutions. Can anyone help?

[ricebike]

do a block test to make sure you didnt blow a head gasket

[theman4444]

ok, so I talked to some shops around and they said that they could do a Combustion and Leak Test for $40, which is totally different from a Compression Test, but they said that this test isn't always accurate.

They said the only real way to see if the head was warped was to pull the head... not helping me.

So I tried bleeding it once more with a certain technique. I ran the car with the bleeder screw off and let it run until no bubbles came out... an hour later... IT STILL HAS BUBBLES COMING OUT!!!!!! But at least it didn't overheat for the hour of running at idle.

So doesn't this prove that it has to have a warped head?

I need professional help.
Modified by theman4444 at 8:22 PM 1/1/2007