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Car Care & Repair Tips - August 15, 2003

What Your Mechanic Doesn't Want You to Know


Comment: The scenario detailed below is an interesting incident from our TrustMyMechanic.com forum. Hopefully, this problem will never happen to you... but if it does, here's what to do...
Austin

Reader Question:

I was driving 35mph in a neighborhood area when smoke started coming out from under the hood of my car. It was caused by coolant squirting from a crack in the radiator expansion tank. Of course, I stopped immediately. The dealer says oil in the coolant and coolant in the oil. They removed the head and saw no visible crack, but pressure testing revealed a crack. They say the engine got up to 300 degrees! I can only think the engine got hot before the crack developed. I asked if there is an audible warning and they say no, the only warning would be the gauge. Can you please advise me on questions to ask the dealer?
Thank you David

Forum Host Response:

Are you still under the factory warranty? If you are, then they should cover this. Don't let them tell you the car over-heated just because the head is cracked. It could have been an existing defect which finally failed. If you do not remember the car over-heating, then most likely the cylinder head failed on its own. If you are not under a warranty, then ask for a firm price, and then shop around for other prices from other experienced mechanics. When they replace the head, have them change the timing belt and water pump while they have everything apart (cheap insurance).
Kevin

Reader Response:

Unfortunately, the car is 6000 miles past warranty. Is there a test or inspection to determine if it was a cylinder head failure? Would there be other symptoms? Are you thinking the cylinder head caused the over-heating, which caused the expansion tank to crack?
Thanks, David

Forum Host Response:

The expansion tank most likely cracked due to the crack in the cylinder head, not over-heating. When the head cracked, the pressure from the combustion chamber pressurized the coolant system and most likely cracked the tank. If the dealer pressurized the head and found the leak, then no more testing is needed. With all the symptoms you described, I would say it was the cylinder head, even if a pressure test was not done on the head.

I am not sure if you can prove the head was defective from the start... you would need a qualified metallurgist to check it out. I own an aluminum foundry so I know how cracks can develop in the casting process. When they replace the cylinder head, they may find a bad water pump, which would blow the theory of a defective head! It's a bit of a guessing game, but no matter what, you need a new head. If you get the water pump changed anyway, you should be safe. Also have the thermostat changed-never hurts, and they are only a few bucks. Good Luck and sorry your wallet will be a little lighter in a few days,
Kevin

Austin's Commentary:

A good machine shop might be able to repair this head, or exchange it for a rebuilt head. I would probably pick up the head from the dealership (if they have removed it already) and take it to a machine shop for "magnaflux and dye checking" to determine if there really is a crack or not. I would imagine replacing this head with a new one at the dealership would be a high-dollar transaction. If the dealership has already torn this engine down, you're pretty much stuck with their services. You don't want to have another shop try to reinstall it...that is a nightmare!

Since this car is only 6000 miles out of warranty and now there is a catastrophic breakdown, I would have the district manager for BMW get involved and investigate getting most of this covered under extended warranty some how. Maybe offer to pay for the labor if they will warranty the parts involved. Cracked head problems are usually seen in cars that were driven until they just flat out quit running or started to run bad because of the excess heat.

I would not expect a car with this low mileage to have a problem that would lead to a cracked cylinder head-unless the driver drove this car until it just stopped due to excessive heat. When this type of driver neglect occurs, there is usually an obvious "BBQ"-type odor under the hood from burnt coolant. Most seasoned mechanics that I know of will tell you there is a certain smell to an engine that "got hot." I would make a visit to the dealership and talk with the mechanic making the repair/diagnosis and ask them if they can tell if this engine really "got hot" or are they scratching their heads as to what really happened. If they have any doubt in their minds I would scream warranty!

Sincerely,

Austin C Davis

Austin C Davis


Interested in an e-book about everything your mechanic doesn't want you to know? Sound advice from Austin Davis. Click Here!


The above article is provided for the interest and entertainment of our visitors. The views expressed in this article are only those of the author, who is solely responsible for the content. AutoGuide.net does not endorse any of these views, and is not to be held responsible for any of the content provided in the above article.


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