Overheating

f00g00 · 06-30-2007, 12:57 PM

Check the seal on the radiator cap, if thats good then you might have a BHG. Mine did the same thing when the headgasket went. One of the pistons was pressurizing the coolant system and would send the coolant out the cap when the pressure overcame the cap pressure.
Fill her up and start the car with the cap off and see if water shoots out of the rad, if it does then more than likely a bhg.

IHateHacks · 06-30-2007, 01:14 PM

The only reason the overflow "overflows" is from a combustion to coolant passage leak, better known as a blown head gasket. Your symptoms are dead accurate.

igosaur · 06-30-2007, 01:57 PM

Many thanks for that.

I did what you said and nothing came out of the top but I suppose that doesn't mean it isn't a bhg!

Looking through the rest of this forum it does seem that this is the most likely cause of overheating and if the only reason for the overflow filling up is this than that's that!

Do you think I could manage this myself or is it a garage job?

Drag0na5h · 06-30-2007, 04:23 PM

I would drive my car home from work everyday and my overflow would take a massive leak all over the ground as soon as I would turn off my car and get out to see it. Well turns out the problem was my radiator cap. The seal was messed up and wouldn't hold the pressure thus sending fluid back into the overflow reservoir. This happened however, after replacing the water pump and thermostat which I believe both had gone bad.

igosaur · 06-30-2007, 04:33 PM

Great, I'll try this first as it's the cheapest and easiest to do

Also, thinking about it the radiator cap does look a bit dodgy..

Thanks.

Quote:

Originally Posted by Drag0na5h

I would drive my car home from work everyday and my overflow would take a massive leak all over the ground as soon as I would turn off my car and get out to see it. Well turns out the problem was my radiator cap. The seal was messed up and wouldn't hold the pressure thus sending fluid back into the overflow reservoir. This happened however, after replacing the water pump and thermostat which I believe both had gone bad.

cre · 06-30-2007, 06:40 PM

Yeah, a bad radiator cap will have your coolant system purging all day long (or until it reaches the point where there's more steam than anything in the coolant system.

The radiator cap is a relief valve. The one our cars come with are largely dependent upon a preset amount of elasticity in the spring. As the spring ages and anneals from the constant heat cycling if begins to open at lower and lower pressures.

BTW - The temperature representation provided by the temp gauge is logarithmic. The temp can go pretty high with little to no movement, even up to arguably hazardous temps. If your temp gauge jumps into the red stop the car ASAP.

1988gte · 06-30-2007, 10:33 PM

Quote:

Originally Posted by IHateHacks

The only reason the overflow "overflows" is from a combustion to coolant passage leak, better known as a blown head gasket. Your symptoms are dead accurate.

Just did a head gasket repair and mine dosent do it anymore, The water jakets on the head were eaten up small leaks in the gasket!! replaced everything that could have caused the problem, but it was a head gasket

cre · 07-01-2007, 04:40 AM

Yup it happens. I just wanted it made clear that there are other things that can cause this problem besides a BHG.

Let's not forget that a faulty rad cap can cause a BHG.

For the benefit of those interested: The radiator is a pressure valve. The higher the pressure in the cooling system the lower the boiling point. Reduce the pressure the boiling point rises. So when a bad radiator cap starts venting coolant too soon it can release enough pressure that your coolant actually starts to boil. Water vapor takes up a lot more room than condensed liquid and the excess volume has to go somewhere. Once this happens both the coolant mixture and water vapor begin purging out of the system through the overflow.... they've got to go somewhere. As this continues the coolant mixture begins boiling more and more rapidly, and as such the purging gains momentum. You can actually end up running on less than half of your coolant in a couple minutes. If you're not paying attention you can overheat big time and then... you guessed it: BHG.

igosaur · 07-01-2007, 09:10 AM

So, here's the plan then.

Get a new radiator cap. If that doesn't work.

Change the gaskets. If that doesn't work.

Put in a new pump. And if that doesn't work.

Sell the car on eBay to someone who wants a challenge and buy another one, preferrebly one with a detachable roof

cre · 07-01-2007, 09:25 AM

Personally I'd start with: Replace rad cap, replace thermostat and pressure test coolant system, before replacing gaskets and the water pump.

06-30-2007, 04:23 PM	#4
Drag0na5h 3" Exhaust Join Date: Jul 2005 Posts: 67	I would drive my car home from work everyday and my overflow would take a massive leak all over the ground as soon as I would turn off my car and get out to see it. Well turns out the problem was my radiator cap. The seal was messed up and wouldn't hold the pressure thus sending fluid back into the overflow reservoir. This happened however, after replacing the water pump and thermostat which I believe both had gone bad. __________________

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06-30-2007, 12:57 PM	#1
f00g00 12psi boost Join Date: Aug 2005 Location: Kuwait Posts: 292	Check the seal on the radiator cap, if thats good then you might have a BHG. Mine did the same thing when the headgasket went. One of the pistons was pressurizing the coolant system and would send the coolant out the cap when the pressure overcame the cap pressure. Fill her up and start the car with the cap off and see if water shoots out of the rad, if it does then more than likely a bhg.

06-30-2007, 01:14 PM	#2
IHateHacks 20psi boost Join Date: May 2006 Location: New Haven/Hamden Posts: 793	The only reason the overflow "overflows" is from a combustion to coolant passage leak, better known as a blown head gasket. Your symptoms are dead accurate.

06-30-2007, 01:57 PM	#3
igosaur 3" Exhaust Join Date: Dec 2006 Location: Gosport Posts: 59	Many thanks for that. I did what you said and nothing came out of the top but I suppose that doesn't mean it isn't a bhg! Looking through the rest of this forum it does seem that this is the most likely cause of overheating and if the only reason for the overflow filling up is this than that's that! Do you think I could manage this myself or is it a garage job?

06-30-2007, 06:40 PM	#6
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	Yeah, a bad radiator cap will have your coolant system purging all day long (or until it reaches the point where there's more steam than anything in the coolant system. The radiator cap is a relief valve. The one our cars come with are largely dependent upon a preset amount of elasticity in the spring. As the spring ages and anneals from the constant heat cycling if begins to open at lower and lower pressures. BTW - The temperature representation provided by the temp gauge is logarithmic. The temp can go pretty high with little to no movement, even up to arguably hazardous temps. If your temp gauge jumps into the red stop the car ASAP.

07-01-2007, 04:40 AM	#8
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	Yup it happens. I just wanted it made clear that there are other things that can cause this problem besides a BHG. Let's not forget that a faulty rad cap can cause a BHG. For the benefit of those interested: The radiator is a pressure valve. The higher the pressure in the cooling system the lower the boiling point. Reduce the pressure the boiling point rises. So when a bad radiator cap starts venting coolant too soon it can release enough pressure that your coolant actually starts to boil. Water vapor takes up a lot more room than condensed liquid and the excess volume has to go somewhere. Once this happens both the coolant mixture and water vapor begin purging out of the system through the overflow.... they've got to go somewhere. As this continues the coolant mixture begins boiling more and more rapidly, and as such the purging gains momentum. You can actually end up running on less than half of your coolant in a couple minutes. If you're not paying attention you can overheat big time and then... you guessed it: BHG.

07-01-2007, 09:10 AM	#9
igosaur 3" Exhaust Join Date: Dec 2006 Location: Gosport Posts: 59	So, here's the plan then. Get a new radiator cap. If that doesn't work. Change the gaskets. If that doesn't work. Put in a new pump. And if that doesn't work. Sell the car on eBay to someone who wants a challenge and buy another one, preferrebly one with a detachable roof

07-01-2007, 09:25 AM	#10
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	Personally I'd start with: Replace rad cap, replace thermostat and pressure test coolant system, before replacing gaskets and the water pump.