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Old 12-17-2003, 03:24 AM
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Join Date: Feb 2003
Location: Buena Park, CA
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How to know if you have a blown Head gasket

Well my car overheated today and I was worried that it might have blown a head gasket. How is this determined? Thanks in advance.
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Old 12-17-2003, 04:23 AM
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Join Date: Dec 2002
Location: Between Oakland and Vallejo, CA
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oil has "milky" or mayo-like apperance
white smoke that doesn't do away with the smell of burnign glycol
rapid overheating
1984 380SL-driving and service privileges.
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Old 12-17-2003, 06:06 AM
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or oil in the radiator.
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Old 12-17-2003, 07:17 AM
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Join Date: Nov 2001
Location: North Central Kentucky
Posts: 1,061
Another common symptom is presure and coolant releasing thru the radiator cap. Most caps are rated for around 15 psi. Presure in cylinders escaping into cooling system will be a lot higher than that.
Most fun (?) symptom is when it gets really bad and you go into hydraulic lock. This happens when the cooling system has been presurized and you shut off the engine. If the leak is bad enough, coolant will be pushed back into the cylinder where the leak is. Then you try to start the car and of course you can't compress a liquid. Engine turns then stops. Only way to get it to turn is to remove spark plugs and let coolant gush out. Had exact thing happen on buddy's BMW 320 (The Ultimate Repair Machine). Lemme tell you, a half litre of antifreeze can get you awfull wet! Don't be a dumb*** like me and stand in front of the open spark plug hole.
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Old 12-17-2003, 10:41 AM
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Join Date: Sep 2002
Location: Los Angeles
Posts: 963
Don't know the exact relationship between overheating and blown head gaskets, but here is what I experienced.

My car overheated 7/29/03, 122,500k, (broken thermostat) and the first hint of oil in the overflow tank appeared in mid October, 124,750k.

The gasket may have been on its way and the overheating may have been the last straw, who knows.

Monitor your oil and coolant comsumption and check your overflow tank and oil often.

1991 300CE
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Old 12-17-2003, 01:12 PM
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Join Date: Jul 2001
Location: SoCal
Posts: 1,303
What I would worry about most is a warped head. Resulting poor contact at the gasket would eventually cause erosion and failure. When the gasket is replaced, the head would need to be planed flat again, at least.

'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7
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Old 12-17-2003, 01:51 PM
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Join Date: May 2002
Location: Mass
Posts: 1,127
Depending upon failure mode, you may get exhaust gasses in the coolant. Sometimes you can see tiny bubbles. Shops can use their exhaust sniffer to diagnose.

Other potential symptoms have been covered well.

Sometimes gaskets holds, but head cracks. Or gasket fails AND head cracks as well. Symptoms are pretty much the same. If you do need a head job, be certain to have the head checked for cracks. Learned this lesson the 'hard' way in my youth...

Of course already you know the short answer is; "don't do that".
Trying to limp those few extra miles is a high stakes gamble.
Tow and rescue cost is cheap insurance.
1986 300E 5-Speed 240k mi.
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Old 12-17-2003, 02:37 PM
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Location: Buena Park, CA
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Thanks guys no sign of anything like that so far. Thank goodness. But I'll be sure to watch for that stuff.
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Old 12-17-2003, 03:49 PM
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Join Date: Apr 2001
Location: Dallas/Fort-Worth
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How long did you continue driving after the overheat incident?

Although overheating may exascerbate the gasket issue, it's "prolonged" overheating that will disable the head, gasket or both.

The engine can sustain the excessive heat for a short duration (or MB wouldn't bother having the gauge register the anomaly). It would be foolish to design an engine where the failure of a mundane $30 component would instantaneously require a thousand-dollar remedy!

I had a heater hose rupture on mine a few months ago, and it took a very hot day and eventual depletion of coolant before the gauge (and smoke coming from the hood) announced the problem.

As stupid as it may seem, I was less than a block from home, so I limped it into the garage.

I replaced the hose a week later, and so far, six months to the day, all is normal with the cooling system...and the head gasket.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car
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