Compression problem?

There are a lot of causes of poor compression, but there are only two general areas for them.

The rings can be worn or otherwise inadequate, or the cylinder walls can be damaged. This is primarily a condition of high mileage; if you have had regular oil changes and the engine is under 200K miles you are not a candidate for that. It is also possible the top compression rings have been broken by detonation ("pinging"), but that's what knock sensors are designed to prevent.

That brings us to the second cause of poor compression - the valves. There are really only two causes of valve trouble of that magnitude also: sticking/burned valves and valves bent by timing belt trouble. Some engines are subject to the valves sticking if the rpms are not run up once in a while; I'll let the Ford experts weigh in if they have heard of such a thing in your engine. Sticking can lead to burnt valves and can cause an engine to fail to start. The other (and more common cause) of valve trouble is timing belt failure. The valves no longer are out of the way when the piston comes up and they get bent. It can do an amazing amount of damage. However, if the tensioner allowed the belt to jump it is also possible the valve timing (and ignition timing) is so far off the engine is not working right. The Gates website indicates the Zetec is not an interference engine, so the scary part may not apply to you. A non-interference engine is not damaged when the timing belt fails or jumps.

If the shop is saying all the cylinders are very low in compression, I'd expect to find the timing belt has jumped badly and may have teeth missing. If some were decent compression and others were very low, I'd look at the other causes.

I'm not familiar with prices for this engine in the Focus, but typically you can expect to pay in the neighborhood of $500 US for a timing belt replacement... call around because prices vary widely. Check your owner's manual - I bet a belt change is overdue if you haven't had it done yet.

Mike

Aside from a near total lack of information, we are left wondering why anyone would focus on the timing belt tensioner and not the timing belt itself.

Rule of thumb with Ford products.... interference engines get chains - non-interference engines get belts. This is not to say that some really talented people can't get bad things to happen any which way.

First step is to check cam timing... this is a relatively simple process if your shop of choice has the documentation (read that as manuals - factory, Mitchel on Demand or AllData). Without these basics (and a healthy dose of experience) your shop is one to avoid.

From the sound of it, this should not be a difficult concern to diagnose...

Michael Pardee wrote: The Gates

The Zetec isn't "supposed to be " an interference engine, but it is. If the belt just snaps, you are usually OK. If the belt becomes loose for a time before it fails due to worn tensioner or idler pulleys, then valve damage almost always results, usually before the belt actually breaks. (The valves hitting the pistons due to retarded valve timing causes stress on the old belt, causing it to break) This scenario happens within in a few seconds. There are usually warning signs, like a slapping or rattling sound at the front of the engine timing cover as the belt gets loose.

Thanks for the clarification. I don't have a lot of confidence in the Gates site, which shows the venerable Volvo "red block" engines as interference although all versions (including the performance K cam version) are definitely not.

I fear your scenario is the most likely. Is a crashed Zetec engine worth repairing or is a replacement the better bet?

Mike

Although I've seen piston or head casting damage on these motors, it's rare. The problem is usually just a couple of tweaked valves. If it were mine I would pull the head and inspect it, then have refurbished or swap in another head. It's not fun, but it's easier than doing the whole engine.

Well, i was told my S10's 2.2 was not an interference motor either. Then my timing chain slipped. Changed the chain. No compression. Pulled the head, 8 bent valves. Go figure.

Bob

Same thing with early GM FWD 3800s. "Not an interference engine" but a failed timing chain usually took out 3-4 valves.

IMO- If the valves are capable of hitting the pistons in any position with the timing belt/chain removed, it should be classified as an interference design. Why are some manufacturers apparently playing word games with this subject?