Mechanic says it’s not the head gasket.

[87 Supra]

Hi, I’m new here but not new to old Toyotas. This is the first Supra I have ever owned and I must say it’s driving me a little nuts. It was dumping coolant out the radiator overflow and over heating so I took it in to be looked at. My mechanic ran all the proper tests looking for a head gasket issue but could find no signs of it. He replaced the thermostat and it stopped overheating. Problem is it still is dumping coolant out the overflow. I saw some leaking out the cap as well so I bought a new one and took it back to my mechanic. He said to drive it and then let it sit over night. If the overflow tank went from full to half full over night then it was another sign that the head gasket was ok. Sure enough it went down overnight and the radiator appears to be full. I drove it to work this morning and the tank was only about half full but there was some coolant on the radiator support near by. I can’t tell for sure where it’s coming from but it looked like the overflow or the very top bar or two of the radiator. My question is can a bad radiator cause this kind of problem? My mechanic seems fairly confident it’s not the head. Sorry for the long read.

-Kevin

[Bman86.5]

hey i knw this might sound crazy but cars are different like person to person. they act up and are finiky. some like to run hot and others run cool, some like to run with extra coolent and some like to run right on the low line, i don't knw why i just notice this with my cars and others that i help with there cars, i hope u find the real cause but sometimes a car will act up for no reason at all just remember that in the back of ur head

[Syris]

Well is there a big coolant puddle on the ground?
What color is the exhaust?

Do you hear any waterfall noises from behind the dash?
Have you burped the system?

[87 Supra]

Originally Posted by Syris

Well is there a big coolant puddle on the ground?
What color is the exhaust?

Do you hear any waterfall noises from behind the dash?
Have you burped the system?

Well like I mentioned earlier it is pushing coolant out the overflow so yes, there is a puddle on the ground. No the car does not smoke; there is no oil in the water or water in the oil. There are no combustion gases present in the radiator and no odd noises in the firewall either. This car is either breaking all the rules or it does not have a head gasket leak. As for burping the system, no I have not done that and really don’t know what that means. I’m guessing getting all the air out. I have ran it with the cap off and its not bubbling out.

[igosaur]

I had the same problem as you for months and yes, it was driving me nuts as well.

Everything suggested that it wasn't the head gasket, exhaust looked fine, no water in the oil and vice verse.

The first thing I did was change the thermostat and this seemed to work for a while but sure enough, not long after my problems were back. Each time it overheated it would dump loads of coolant in the expansion tank and sure enough, the next morning it was back in the radiator.

Eventually I have come to the conclusion that it was a succession of dodgy hoses. Each time I had an overheating problem I would listen carefully under the bonnet, with the engine off of course, and more often than not I could hear a hissing sound.

I have now repaired or replaced at least 4 hoses and changed the clips on countless others and, touch wood, no more problems.

It just takes a small split in a hose or a badly fitted hose to stop the whole system becoming pressurised properly and so it boils and either pops a hose or dumps coolant into the tank.

I also did an oil change and added some oil additive to keep the engine as cool as possible.

[mizuboi]

by burping the system we mean raising the front end as far as it will go and run the engine for about 20 minutes and then fill the coolant as necessary that should help otherwise you might want to check the connectors onthe thermostat. check the dual vaulve on it too you know the blue one with two ports comming out of it...well thats all i can think of off the top of my head

and yes a bad bent old radiator can cause this also clogs in the places where the coolant goes

my girlfriends na did that for a while it lost coolant in teh system somewhere and then an hour or two later it threw it all up out the overflow tank so burping solved that well hope everything works out for ya

[87 Supra]

Originally Posted by igosaur

I had the same problem as you for months and yes, it was driving me nuts as well.

Everything suggested that it wasn't the head gasket, exhaust looked fine, no water in the oil and vice verse.

The first thing I did was change the thermostat and this seemed to work for a while but sure enough, not long after my problems were back. Each time it overheated it would dump loads of coolant in the expansion tank and sure enough, the next morning it was back in the radiator.

Eventually I have come to the conclusion that it was a succession of dodgy hoses. Each time I had an overheating problem I would listen carefully under the bonnet, with the engine off of course, and more often than not I could hear a hissing sound.

I have now repaired or replaced at least 4 hoses and changed the clips on countless others and, touch wood, no more problems.

It just takes a small split in a hose or a badly fitted hose to stop the whole system becoming pressurised properly and so it boils and either pops a hose or dumps coolant into the tank.

I also did an oil change and added some oil additive to keep the engine as cool as possible.

Yea, that sounds just like what I have going on here. After the thermostat replacement the car has not overheated but sometimes it still dumps it out the overflow. I’m leaning toward a small radiator leak. Maybe near or around the overflow bottle.

[87 Supra]

Originally Posted by igosaur

I had the same problem as you for months and yes, it was driving me nuts as well.

Everything suggested that it wasn't the head gasket, exhaust looked fine, no water in the oil and vice verse.

The first thing I did was change the thermostat and this seemed to work for a while but sure enough, not long after my problems were back. Each time it overheated it would dump loads of coolant in the expansion tank and sure enough, the next morning it was back in the radiator.

Eventually I have come to the conclusion that it was a succession of dodgy hoses. Each time I had an overheating problem I would listen carefully under the bonnet, with the engine off of course, and more often than not I could hear a hissing sound.

I have now repaired or replaced at least 4 hoses and changed the clips on countless others and, touch wood, no more problems.

It just takes a small split in a hose or a badly fitted hose to stop the whole system becoming pressurised properly and so it boils and either pops a hose or dumps coolant into the tank.

I also did an oil change and added some oil additive to keep the engine as cool as possible.

Thanks! I will try that this weekend and see what happens.

[ddmcse]

watch the over flow bottle and keep fluid in it

if you have to keep filling it on a regular basis ,,, guess what
you have a bhg and you can continue to drive for thousands of mile this way before you finally have to throw in the towel ...

[ethan12510]

Originally Posted by ddmcse

watch the over flow bottle and keep fluid in it

if you have to keep filling it on a regular basis ,,, guess what
you have a bhg and you can continue to drive for thousands of mile this way before you finally have to throw in the towel ...

its safe to drive with a bhg?