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flyerfolife 01-02-2016 01:18 PM

Coolant not flowing back from expansion tank
Searched all the threads I could, mostly everyone says its a blown headgasket.

Hey all and a Happy New Year! :tongue:
I have a 2000 SH with 183k.
Early november, my car started to overheat. I checked my coolant level and had to add almost 3/4th gallon of coolant. I did notice my expansion tank was overflowing. I assumed that it was a t-stat problem or radiator cap or something. Since then I always kept an eye on my temp gauge and coolant level, and everytime I added coolant my expansion tank was always full and I would drain it out to between the MIN MAX marks. Recently last week I finally got the time to check things out. I could not find any coolant leaks anywhere. My spark plugs were whitish gray (I am asuming from the few times it started to overheat, my compression numbers read 180 180 150 150, I did not have any oil in the coolant or coolant in oil, and I found one of the rubber rings on my rad cap was torn. Replaced it with one of those caps with a pressure release lever. Still have the same problem.
Is there anything else I can try to narrow down a possible blown headgasket?
Could my radiator cap still be the culprit? I have never had one of the ones with the pressure release switch, to me it just sounds like another place for pressure to escape so the coolant is not being drawn back in.
The car runs like the day I bought it 2 years ago, no white smoke, no noticable loss of power. thanks in advance

flyerfolife 01-04-2016 03:02 AM

Re: Coolant not flowing back from expansion tank
bump, anyone?

Amazon 01-05-2016 06:51 PM

Re: Coolant not flowing back from expansion tank
You fluid is going somewhere, so you'd have to assume you have a leak, whether it be a cracked radiator, leaky cap, or blown head gasket. How often are you adding coolant to the reservoir, weekly? Have you tried to bleed the line after adding fluid?

If it was a leaky radiator cap, I'm fairly certain you would have noticed white specs and spatters from dried fluid on the radiator hoses and surrounding area, you'd also probably notice the sweet smell of antifreeze present, especially after running the engine. A small crack in the radiator could be possible, fill up with fluid, crank it up, and hang out in front of the car looking for drips.

Other possibility is a blown head gasket. I didn't even know mine had blown until I started getting a fluctuating idle, even then, there was no apparent evidence of oil in the fluid or fluid in the oil. only after a month or two did the signs of a blown head gasket start to appear.

Noober 01-06-2016 12:56 AM

Re: Coolant not flowing back from expansion tank
When my head gasket went at 245k miles, only symptom I noticed was the reservoir kept boiling over after 20 min or so of driving. Even then performance never dropped and if I ran the heater the boil over was very minimal.

skyhigh 01-12-2016 07:28 AM

Re: Coolant not flowing back from expansion tank
Check your Overflow hose for leaks.

Scout1 01-18-2016 10:52 AM

Re: Coolant not flowing back from expansion tank

Don't know if you got your answer or not. I just went through this on one of my son's Honda civic. If you have a compressor you can pull all your spark plugs. Get each cylinder one at a time to TDC on it's compression stroke and then put about 100 psi to each cylinder. Have your radiator cap off and your radiator full. Watch the water level at the radiator filler neck. If you have a bad head gasket or a crack somewhere then the water will flow out or start bubbling. There are some chemical testers you can rent at some parts stores but I have tried those and I didn't get good results.


bykfixer 01-18-2016 10:00 PM

Re: Coolant not flowing back from expansion tank
^^ good tip Scout

Those plastic radiator housings can crack around the cap. So small you do not see it at times.

And the lack of pressure build up can cause flow issues.

Sometimes those factory pinch style clamps allow coolant past at high pressure when they were re-used more than once. They should be replaced when the hoses are.

If your exhaust still steams after like 20-30 minutes of running that could be a sign of a small leak.

If I'm not mistaken the white soot on your plugs is a sign it's running too has a pre-burn issue from mis adjusted intake closing too soon.

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