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How to check for a blown headgasket

13K views 22 replies 12 participants last post by  kotetu  
#1 · (Edited)
oil check:
Look at the engine oil dipstick, or look at the under side of the engine oil filler cap. If the oil is contaminated with antifreeze, it will have the appearance of a chocolate milkshake. Do not start the engine if the oil is contaminated with antifreeze, as serious internal engine damage can result.

air compressor check:
Remove one of the rear sparkplugs and the radiator cap. Fill the radiator and then push some air into the sparkplug hole (get a good seal in case a valve is open). Repeat with all the cylinders and watch for air bubbles coming up into the radiator. If bubbles come up or fluid is pumped out, the head gasket is blown and must be replaced.

The only problem with checking the oil cap is that they placed the cap in the engine's highest location (besides the intake manifold, which doesn't have oil in it), so any condensation from the engine (somewhat normal) will rise and collect on the oil cap. A little bit is ok, too much is bad.

The best way I found to check? Buy a spill proof funnel, connect it to the radiator, then fill it up with coolant. Start the car and let it run. If an endless amount of bubble reach the top, or the coolant level is constantly going down, then you either have a leak or a blown head gasket. After that, pressure test the cooling system and if there are no external leaks, it's a blown head gasket.

Another way to tell is to drive the car and keep constantly bleeding the coolant. If you still get air bubbles and you're losing coolant after a week or so, then you have a blown head gasket.
 
#2 ·
I needed this a couple months ago. Never had a clue how to do it. Got a tool loan from Auto Zone and it had no instructions. People at the counter were tools themselves and knew nothing so I just returned it. I think it had something missing out of the case though.

Thanks
Rochelle
 
#3 · (Edited)
The only problem with checking the oil cap is that they placed the cap in the engine's highest location (besides the intake manifold, which doesn't have oil in it), so any condensation from the engine (somewhat normal) will rise and collect on the oil cap. A little bit is ok, too much is bad.

The best way I found to check? Buy a spill proof funnel, connect it to the radiator, then fill it up with coolant. Start the car and let it run. If an endless amount of bubble reach the top, or the coolant level is constantly going down, then you either have a leak or a blown head gasket. After that, pressure test the cooling system and if there are no external leaks, it's a blown head gasket.

Another way to tell is to drive the car and keep constantly bleeding the coolant. If you still get air bubbles and you're losing coolant after a week or so, then you have a blown head gasket.
 
#6 ·
Yes but a newbie might not.

Even a quality mechanic can miss it if it is in the early stages and they are doing a short inspection. My advice if you are buying a Legend is to look at it when the engine is bone cold before test drive. Open the radiator cap and see if the coolant level is all the way up. If it isn't completely filled, even if it is only a teacup's worth low then walk away, unless of course you don't mind replacing the headgasket or engine. BTW don't let any mechanic sucker you in to thinking it is an easy or cheap fix because it isn't. Anybody who says so is full of crap. Not to mention that if the engine got hot enough the steel lining of the cylinder may have delamited and you may have cylinder walk that will destroy the gasket in another 50k.

I wish I had known. My mechanic missed the BHG when the car was prepurchase inspected because the leak was so small it wasn't even showing up on the hydrocarbon test. The only evidence I got was when the car overheated after 2 or 3 days because the thermostat got caught in an airbubble. Even when I took it back to two different mechanics after that happened Hydrocarbon test still showed nothing. Oh and the guy who checked my car knows his sh#t. He swapped the ZC in to my Honda and did an outstanding job not to mention all of the other major maintenance on that car for the last 100,000k miles. So he didn't miss it because he didn't know what to look for.

As long as I kept coolant in the car it ran well for 8000 miles after that but the leak has finally gotten bad enough that overpressure in the coolant system is a danger to the radiator and everything else in the cooling system.

None of the other signs have been there though. The Heater works fine, there's no coolant in the oil, no major idle issues, no oil in the antifreeze, nothing at all except the constant loss of coolant and overflow being pushed out of the reserve tank.

Now every time I see another Legend I look for that white smoke and I would bet you that at least 3 out of 10 have it. My second piece of advice on buying the car is don't buy it if you can't afford to maintain it. Like my mechanic said you might have only paid $5k for it but you are paying for service on a $30k car.

Regards
 
#7 ·
Another method is to pressure check each cylinder. The cylinders at top dead center should be, IIRC 180PSI each. If you are reading significantly below that then chances are you have a blown headgasket OR you're rings aren't sealing properly. However, the later problem is very, very uncommon in the 3.2L Legend engine.
 
#18 ·
johnnie34;1038481 Now every time I see another Legend I look for that white smoke and I would bet you that at least 3 out of 10 have it. Regards[/QUOTE said:
Chit, down here, its like 8 out of 10. I even c the baddest ones with twinkies,tv's..... but they must forgot how to open their hood and put some money in that too. Its crazy cuz i been there, so when i c one, i just look like i bet u it smoke.Its gooten so bad , my girl will come home and say chit like, this dude try alk to me wit a Legend today, and he shit was smoking bad. She said she wanted to tell him keep straight till u get to the dealership cuz u got a bhg.
 
#21 ·
What's the standard way to check the compression level of each cylinder? A family member has one of those Craftsman compression kits. do you remove each sparkplug, and put it into where the sparkplug would go one at a time and crank?

Also, wouldn't a BHG be found if one cylinder's PSI is a drastically different reading than the others vs the all lower or higher theory?