I've had a bunch of problems with my truck (2000 Ford Ranger) and I've been hoping to sell it. Most recently, I was driving it and the heater control valve snapped. I drove it home and replaced the heater control valve and the first time I took it out, the heat wasn't working and it eventually started to overheat. I pulled it over and had it towed to the mechanic, then said I wanted it fixed so I could drive it again, but also that I'd like to have him look it over to see what kind of stuff I would need to fix before selling it (so that I didn't end up pawning off some death machine on someone).

The next day, the mechanic told me that the compression in all the cylinders is way low, and that it would be very expensive to fix because the engine would need to be replaced or rebuilt. They said that the overheating problem is also being caused by the bad compression because the coolant isn't being routed the right way.

Normally I would not be surprised if it were a problem like bad compression, since the truck has consistently had a number of issues, and is always incredibly slow to start until it gets warmed up, but the one thing that is giving me pause is that the guy who runs the mechanic shop and one of his mechanics are both eager to buy the truck. I think the price they've offered is fair considering the expense of the repairs, but I'm a bit worried that they have an incentive to tell me the problem is worse than it is.

Personally, I'd love to be rid of the thing and not have to deal with this anymore (given the problems it has given me), so I'm happy to accept their offer if the compression is the problem. Can anyone tell me if these sound like problems that could be caused by bad compression?

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    It doesn't sound right to me, though I'm not thinking well enough right now to give this a glorified answer. My best advice to you right now is to get a second opinion. Don't tell whomever you take it to you are thinking of selling it or what the first mechanic said. You obviously have some issues. I'm not mating the low coolant flow with low compression, it just does not compute ... but, maybe it's a Ford thing. Commented Dec 4, 2014 at 1:33

2 Answers 2


If you don't get heat into your cabin, it's usually because of a blocked radiator. That would explain your overheating too. Unfortunately, that ALSO means that you could have damaged your head gasket, which would explain the low compression and difficulty starting.

They don't sound particularly shady to me. Given your history and your current problem with the truck, there is a very good chance that they're telling you the truth.

Keep in mind that rebuilding an engine will cost YOU a lot of money in labour and parts but if the mechanic buys the truck from you and keeps it for himself, he can work on it on his own time without spending anything on labour and he probably has at least half the parts needed for a rebuild lying around the workshop.

I would guess that it would cost you $4000 for an engine overhaul, whereas it would cost a guy who owns a workshop $1000 in parts and nothing in labour.


The circulation of the coolant through the engine is by the engines water pump. Low compression would effect the performance of the engine, but not the circulation of the coolant. You proberbly have an engine that is not timed up correctly if all the compressions are all low, cams out for instance.

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