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Woe or miracle: did the pistons miss the valves?

Here’s a tale of either woe or miracle, depending …

I tried saving my college-student daughter some $$ by changing the timing belt and water pump in her '01 CRV. The job went fine (minimal tears and almost no blood) and it ran great (as before) for several weeks until the crankshaft bolt fell off at 55 mph (didn’t get it tight enough) and the key holding the timing sprocket fell out, which stopped the cams.

I thought I’d surely have to pull the head for a valve job. But when I got it all back together, the engine still runs great. It seems slightly noisier than before, but since I don’t normally drive it I can’t tell if it’s different.

So, did the pistons manage to miss the valves (a true modern-day miracle)? If the valves are just slightly bent, by driving it as-is, am I risking damage to the pistons, head, catalytic converter, and left rear turn signal bulb, as my mechanic suggests? A compression test will cost at least $45 - should I have one done?

It would be worth a few dollars to have a cranking compression test done, yes. Otherwise one or more damaged valves may become symptomatic in the near future prolonging your headache.

Why not take the $45 and buy a compression tester instead? That way you only spend that money once & use it whenever you want.

Possibly the engine is not an interference engine, meaning that when this happened the valves and pistons do not collide. If it is running OK, then the valves probably are OK. I would wait and see.

I borrowed a tester from Autozone and tried it but couldn’t figure out how to really use it. The gauge would jump to somewhere between 60 and 90 psi (book says ~140 psi) on each compression stroke and then fall right back down. Surely I used it wrong - the compression can’t be HALF what’s called for and still run well, can it?

Every source I’ve found (people and on-line) says it’s an interference engine.

Sounds like the gague was leaking, if you got 60-90 on one pump you may well have 140 if the gague didn’t leak, get another gague and try again.

Yep; that’s very possible. The plugs on the engine are sunk way (about 5 inches) down into the valve cover. I had to “tighten” the gauge by just twisting the hose.

There are varying degrees of interference. Some engines are only in real danger of damage if they are revving high when the cam connection breaks. Some only have minimal interference and will cause a little bend in a few valve stems, but not enough to make the car run poorly. Some will mutilate valves and piston faces.

It’s likely that you have some just slightly bent valves, that would explain the noise. Over time, landing off-center will probably deform the valves and seats slightly but there are two things to keep in mind here:

First, who knows how much longer it’ll last in its current condition. It may go another 30k before the valves stop sealing to the point where it’s got drivability problems.

Second, there are about a zillion of these motors out in the world, it shouldn’t be hard to find a complete rebuilt head when the time comes, bolt it on, and call it a day. Not a big job on the CRV (my girlfriend also has an '01 CRV, I’ve seen under that hood, head swap could take an amateur shade tree mechanic a weekend).

This is pretty reassuring. I had planned on a weekend to pull the head, so that sounds about right for my skill (or lack thereof) level. So, I take it you don’t see substantial risk of more damage by running the engine if the valves are slightly bent?

When I tighten the crankshaft bolt on an automatic, I use an air impact gun.

Go ahead and do a compression leakdown. If it’s losing compression, then you are in a little bit more of a dire a situation. If the compression is okay and you don’t have drivability issues, then just let her drive it until it starts burning oil and running badly.

But yeah, swapping the head on that thing should be a reasonably simple procedure if you have a manual, a good set of tools, and a weekend.

I don’t agree with the 140 PSI figure either. The general rule of thumb (varies by altitude, barometric pressure, etc, etc.) is approx. 18-20 X the compression ratio.
This means 18-20 X 9.6 or roughly 175-190ish PSI on a good engine.

Also keep in mind the CRV has mechanical lash adjusters and CRVs have had some problems with the valve lash recommendation. Honda recommends in excess of 100k before even inspecting them and in reality this should be done every 30k miles.
Not every factory recommendation is a good one and Honda is not the only guilty one here either.

You could get a vacuum gauge (cheap and easy), connect it to a manifold vacuum source, and see what you get for a reading.
If there’s a compression issue due to the valves it will show up immediately on the vacuum gauge and if so, then it’s back to a better check of the compression along with determining if some valves are slightly bent or misadjusted.

Here’s one of many blurbs about the lash problem.

Might want to add—some Loctite on the crank bolt (the kind you can still disassemble with normal tools) may be just the thing.

Yeah, I certainly thought about something along those lines. Don’t want it to come of AGAIN! I think I’m actually going to take it to the dealer and have them torque it down. With the engine cover off, it should take literally about 2 minutes. Surely they won’t charge too much.

You don’t say what engine the vehicle has. I have a listing of the Honda engines from ALLDATA and the only engine that are not interference engines are the 3.2 and the 3.0.

The Gates Timing Belt Site Agrees With Bill Compton … Can You Say, “Interference?”