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Monday, September 20, 2010

Automobile Repair Dilemma

The car-car (2001 Chrysler Sebring) blew up. I had it towed to Eric's shop. He thinks a head gasket has blown. Only way he will fix it is to replace the motor with a rebuilt one. It's an aluminum V6 and it's had some cooling problems. I thought these problems were minor, but evidently aluminum engines are more sensitive to this stuff.

Head gaskets blow when the head warps, usually from overheating. Problem with aluminum engines is that oftentimes the block will warp as well, so to do a proper repair, the block needs to be resurfaced (machined flat) as well as the head. To do that, you really need to completely disassemble the engine. If you are going to do that, you might as well just buy a remanufactured motor, and that runs between $2500 and $4500, depending on whether you buy it locally, or buy it over the internet from an East Coast engine rebuilder and have it shipped across the continent.

On the other hand, I could haul the car home, pull the engine out in my garage, pull the heads off and send them to the machine shop, and apply a file to top of the block. Of course, this is a bit risky. It depends on:
  • the blown head gasket being the only problem,
  • the block not being excessively warped and
  • being able to pull the studs out of the block. (Better presume there are studs, not head bolts. That would be too easy.)
All kinds of things could go wrong here. A file is good for knocking off high spots, but if there is a low spot, that means the whole surface would need to be taken down, and that is a job for a milling machine, not a file. Then there's the debris problem. Filing creates little bits of metal, most of which will be captured by rags, cleaned up with a vacuum or blown away by compressed air. However, by the nature of machinery some of the smallest specks will fall unnoticed into places where they will lie, waiting for their opportunity to wreak havoc on some sensitive part, like a piston ring.

What to do? Do I invest a bunch of time and energy on a possible cheap fix? Or do I bite the bullet and spring for the new motor? The car is worth just enough to make replacing the motor worthwhile.
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4 comments:

  1. Rocky HumbertSeptember 21, 2010 at 6:13:00 AM PDT

    I will wager you a bottle of fine champagne that if you rebuild the engine yourself, it will not last one year or 5,000 miles ... which ever comes first. However, to engage in my wager, you will have to provide documentation that you actually rebuilt the engine yourself. A video tape is acceptable proof.

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  2. Chuck PergielSeptember 21, 2010 at 10:40:00 AM PDT

    Cool! A challenge! But I would want different terms. If my repair lasts 80,000 miles (which is how many the car has on it now), I'll be ecstatic and want to celebrate & I will buy you a bottle of fine, well, decent, champagne. If my repair fails within a year, I'll be devastated and need some consoling, so you'll buy me a six pack of Bud.

    Actually, if I complete the repair and the thing actually starts and runs I'll be ecstatic. That would be the time to celebrate. Let's see if I get that far.

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  3. CGHillSeptember 22, 2010 at 7:58:00 PM PDT

    I used to have an '84 Mercury with Ford's 232 V-6. Iron block, aluminum heads, different coefficient of expansion, inadequate gaskets. After the third cracked head, I sent it away and bought a Mazda. It, too, had an iron block and aluminum heads, but it never came close to blowing a gasket.

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  4. Chuck PergielSeptember 22, 2010 at 8:21:00 PM PDT

    Yeah, I don't know how they make that aluminum head / iron block thing work. Like you say, different coefficient of expansion. I think our old Ford Windstar was like that. I sent it in to the dealer for service one time and they volunteered to replace the head gaskets. It never gave me any trouble in that department.

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