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Mazda Losing It's Head

Q. Our 1993 Mazda MPV 4WD (110,000 kms) overheated and was driven for about 3 kms - inspection revealed oil mixed in the coolant, so gasket was suspected. The dealer (where we bought the car 3 months ago) now says we have 2 cracked heads, which he will replace with reconditioned heads. Total cost about $3,000 (cdn), of which he will pay $1,000 as a goodwill gesture.

1. Is this good money after bad? Can the dealer easily tell if there is further damage to the bottom end?
2. should I be suspicious of 2 heads going at the same time?

This car, according to the dealer, was serviced religiously but driven very slowly by its previous owner - trans was replaced at 95,000 kms.


A. They make it sound like this vehicle was owned by a little old lady who only used it to drive to church on Sundays. Hmmm... where have I heard that before?

This is an interesting question. Now I'm going to assume he has pulled the heads off and sent them to a machine shop to have them inspected. There is no way to tell if a cylinder head is cracked just by looking at it. Steel heads can be magnafluxed and aluminum heads have to be pressure tested. I have never seen a dealer that has the equipment to do either test.

If the heads are still on the vehicle, then I would tow the vehicle out of there and find another shop. If he's telling you you have two cracked heads without taking them off and sending them out for testing, he's someone you don't want working on your car. Personally, I would tend to look at the head gaskets. To me that's a far more likely possibility.

The red alert went off when he said both heads are cracked. Now it is possible, but not very likely. He may be looking to make the job easier for himself by doing a quick turnaround job. Standard practice is to send the heads out for testing, and if they pass, they are rebuilt as required. This may or may not include cutting the valves and valve seats, otherwise known as a valve job. All of this takes time, time your car is sitting in the shop waiting for the heads to come back. If he can send your heads out and get two right back, he has you in and out.

Is this good money after bad? That's a difficult question to answer. Can you replace this vehicle with a comparable one for the same money. If the answer is yes, I would consider it. If you like the car and you're comfortable with it, then have it repaired. After all, the devil you know is better than the devil you don't. I have found over the years that Japanese cars don't mind having the heads replaced, even with high milage. American cars on the other hand, aren't crazy about it. Sometimes when you replace the heads on an American engine, they usually start sucking oil up past the rings. This rarely happens with Japanese engines.

Short of taking the oil pan off and looking at the bottom end, and in the absence of noises, there is no way to really tell what kind of shape it's in. It takes a lot to hurt the lower end. Personally I would do the job and not worry too much about it. Damage will occur if bearings are run dry, not with an oil/antifreeze mix.

If you decide to go with this shop, get everything in writing. Let him see you are watching him closely. He's less likely to try and pull a fast one when he knows he's being scrutinized.

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