One Overheated Owner?

Sunday, March 15, 2009

Dear Tom and Ray:

I have a 2001 BMW 325xi, which I have serviced regularly at a local independent BMW mechanic. The shop came highly recommended, and I've never had reason to question that. But last week, the coolant light came on. I took it in to get it topped off. They told me my water pump needed to be replaced, so I did it -- $450. Two days later, while idling in a parking lot, the car went boom! The shop now tells me that the coolant expansion tank blew, and that it's not related to the work they just did. That was $600. No problems with the cooling system for seven years, then two in two days? -- Laura

RAY: I don't think this is necessarily a crisis of car or mechanic. The most common reason a coolant expansion bottle explodes is because the car overheats.

TOM: And it's possible that the overheating was your mechanic's fault.

RAY: If they didn't bleed the cooling system correctly after replacing the water pump, they could have left air in it. Air doesn't do nearly as good a job of cooling the engine as coolant does. That could have led the engine to overheat and blow up the expansion tank.

TOM: But that's not necessarily what happened. Your thermostat could have gotten stuck after the water pump was replaced -- just a coincidence. Or the thermostat may have been the reason the coolant light came on in the first place, and they just happened to notice that your water pump was leaking and assumed that was the issue.

RAY: The worst-case scenario is that all of this overheating is due to something like a blown head gasket.

TOM: Keep an eye on the temperature gauge for the next few weeks. If it's normal, I think you're all set.

RAY: But if you notice that the engine is running hotter than usual, take it back and ask your guy to investigate a little further.

Dear Tom and Ray:

My husband's 1997 Nissan pickup's horn honks every time the steering wheel is turned. The problem started with a clunking in the steering wheel and progressed to the honk, which sometimes will not quit until you bang on the steering wheel. We are at our wits' end as to what to do. -- Jackie

TOM: And in all this time that you've been ticking off your entire community, it never occurred to you to take it somewhere and have a mechanic look at it?

RAY: Well, that's what we're going to recommend now. There are three likely possibilities. One is that the horn contact -- the horn button itself -- has come loose and is floating around in your horn pad.

TOM: We don't recommend that you remove the horn pad yourself, since that also houses the air bag.

RAY: It can be done safely if you disconnect the battery and allow the air bag to power down for a while before disturbing it.

TOM: If the problem is not right there under the horn pad, then someone will have to pull off the steering wheel and figure out if the problem is in the multi-function switch or the steering column wiring.

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Copyright 2007 by Tom and Ray Magliozzi and Doug Berman

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