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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oil has "milky" or mayo-like apperance
white smoke that doesn't do away with the smell of burnign glycol
rapid overheating

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1984 380SL-driving and service privileges.

or oil in the radiator.

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.

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.

glenmore
1991 300CE

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.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

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.

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1986 300E 5-Speed 240k mi.

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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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.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

I have white smoke coming out of exhaust pipe. All smoke and no indication of water dripping. The engine does not heat up rapidly and I've not seen oil in overflow tank. The engine runs normal, cranking to run condition is quick, idle seems normal. Very confusing. 1985 380SE with 103,000 miles.

oil floats on water,check oil,if smoke is sweet smelling,either head gasket,or crack block.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

Saying a car has a bad head gasket is a default description that is frequently miss applied to various ills.

For engines in general, a head gasket can fail in these modes, listed most frequent to least.

Cylinder to coolant ( Possibly what your issue is )

Cylinder to cylinder

Coolant to outside the engine

Coolant to oil / oil to coolant

The _only_ way to test for cylinder issues is to do a leak down test. This is accomplished my removing spark plugs, turning a piston to top / both valves closed then pumping in about 100 PSI of air. You then look in the rad cap to see if the level rises or bubbles form. If is does, there is a breach between the cylinder and coolant. This can be a bad head gasket , cracked head. Cracking a block ( cylinder ) on a regular engine is exceedingly rare.

Any other method will be inconclusive and non productive.

Pressurizing the cooling system will uncover coolant to outside of engine. Coolant / oil issues will be apparent by looking at each fluid.

Also be sure to pull the hose from the automatic transmission vacuum modulator, it can fail and allow transmission fluid to be burnt causing smoke.

I had a head gasket starting leaking very slowly. The 12 months or so before I realized it, I noticed a white residue on many of the coolant hoses. The only thing I can think of is exhaust gases in the coolant somehow permeated the rubber hoses and evaporated on the exterior, leaving a white, dusty-looking residue that wiped right off. The residue ended exactly where the radiator necks began, so there's no question that it was directly related to the coolant inside the hose.

Strangest thing...

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Suppose you were an idiot, and suppose you were a member of Congress; but I repeat myself. - Twain

What you describe is common, I've seen it on cars with perfect engines.

Coolant slowly wicks between the hose and neck then evaporates. Generally, the white stuff is the additives in coolant that don't evaporate.

Sometimes there's no oil contamination of the coolant. Sometime, like in my present 1990 300SEL, the head gasket leaks oil externally down the side of the engine. I'm told that it's actually very common in 175K mile engines that don't have the "milk shake" condition in their coolant.

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03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio