Help With Overheating Please
Thread Starter
Instructor
Joined: Jan 2008
Posts: 149
Likes: 8
From: Scarborough Qld
Help With Overheating Please
To make a long story short.
Went for a drive yesterday & noticed the temp got up over where it usually sits.
Stopped the car & checked under the bonnet & found the coolant dripping out of the expansion tank (very slowly).
I waited for the engine to cool down a bit then headed home at very slow revs. The temp crept up even higher & just before I was about to panic, it plummeted down to normal.
HERE IS THE QUESTION
Could it be possible that there was an air lock under the thermostat that prevented hot water opening the thermostat??
If this was the case, did the trapped air finally get hot enough to cause he thermostat to open???
I have heard of people drilling a small hole in the thermostat to prevent trapped air. Is this the right path to take?
Any help would be greatly appreciated.
Thanks in advance.
BTW. Normal temp is about 93, the guage went up to 120.
& I should mention its in celsius here Downunder.
Went for a drive yesterday & noticed the temp got up over where it usually sits.
Stopped the car & checked under the bonnet & found the coolant dripping out of the expansion tank (very slowly).
I waited for the engine to cool down a bit then headed home at very slow revs. The temp crept up even higher & just before I was about to panic, it plummeted down to normal.
HERE IS THE QUESTION
Could it be possible that there was an air lock under the thermostat that prevented hot water opening the thermostat??
If this was the case, did the trapped air finally get hot enough to cause he thermostat to open???
I have heard of people drilling a small hole in the thermostat to prevent trapped air. Is this the right path to take?
Any help would be greatly appreciated.
Thanks in advance.
BTW. Normal temp is about 93, the guage went up to 120.
& I should mention its in celsius here Downunder.
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
The answer to all your questions is 'yes'. If the engine has now cooled back to ambient temps, remove the radiator cap and see if the coolant level has dropped from it's previous level. Top it up to no more than half way up the expansion tank.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
This is both a common problem and one that is usually overlooked. By the time the engine bay is being inspected the hose looks normal again. Only when hot and under fluid suction does the hose collapse causing restricted fluid movement.The easiest way to check is to start the engine, and move the throttle up raising the RPMs and watching the lower hose. You'll usually see is sucking in and sometimes you can hear the gushing of fluid as it tried to sneak past the inner walls.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You might also have a 'sticky' thermostat...maybe binds-up and won't open until it gets too hot. You can check it by throwing it in a pan of water on the stove and heating until it opens. It should open smoothly. If not, replace it [and its gasket].
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
From your description, do this first. But I would just replace it anyway.
Thread Starter
Instructor
Joined: Jan 2008
Posts: 149
Likes: 8
From: Scarborough Qld
Update
I topped up the radiator ( I have a cap on the hose between the radiator & the thermostat), went for a drive, & the temp came up to 93 & stayed there.
Looks like there must have been an airlock because the fluid was low.
The lower hose did not collapse at higher revs when hot.
Thanks for all the help & I will replace the thermostat when I get the time. I will also drill a small whole in it to allow the air to escape should this happen again.
Looks like there must have been an airlock because the fluid was low.
The lower hose did not collapse at higher revs when hot.
Thanks for all the help & I will replace the thermostat when I get the time. I will also drill a small whole in it to allow the air to escape should this happen again.
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Burning Brakes
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Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I topped up the radiator ( I have a cap on the hose between the radiator & the thermostat), went for a drive, & the temp came up to 93 & stayed there.
Looks like there must have been an airlock because the fluid was low.
The lower hose did not collapse at higher revs when hot.
Thanks for all the help & I will replace the thermostat when I get the time. I will also drill a small whole in it to allow the air to escape should this happen again.
Looks like there must have been an airlock because the fluid was low.
The lower hose did not collapse at higher revs when hot.
Thanks for all the help & I will replace the thermostat when I get the time. I will also drill a small whole in it to allow the air to escape should this happen again.
Where? The fill cap? The nipple where a cracked hose might be connected? I do know that sometimes small pinholes can develop in those tanks and they weep fluid when under pressure.Narrow down the leak because the fix depends greatly on the specific problem.
Thread Starter
Instructor
Joined: Jan 2008
Posts: 149
Likes: 8
From: Scarborough Qld
The dripping colant was not a leak so much as overflow from the cap under high pressure. Should I put an overflow tank for the times that there is too much coolant in the expansion tank?
Thread Starter
Instructor
Joined: Jan 2008
Posts: 149
Likes: 8
From: Scarborough Qld
I tested the thermostat today. Its only 2 years old, & opened smoothly. I drilled a small hole in the thermostat to let the air escape, & then fitted it with a new gasket, flushed the radiator & changed the coolant (its been about 2 yrs since last change).
I have an upper hose with a filler cap on it & today was the first time that I have seen coolant there when I started the engine. It filled very slowly, indicating that the hole in the thermostat was doing its job without allowing too much coolant through.
I went for a small run to get the temp up, then let it idle for a while. Everything went to plan. Next I will go out for a longer run & post an update.
Hope Ive done the right thing with the thermostat.
I have an upper hose with a filler cap on it & today was the first time that I have seen coolant there when I started the engine. It filled very slowly, indicating that the hole in the thermostat was doing its job without allowing too much coolant through.
I went for a small run to get the temp up, then let it idle for a while. Everything went to plan. Next I will go out for a longer run & post an update.
Hope Ive done the right thing with the thermostat.