Is it possible to bend just one valve?

timing-belts
geo
belts
tracker

#1

I took an eight vale 1994 Geo Tracker to the shop for a water pump replacement. They correctly suggested that the timing belt should be replaced too as most of the labor would have to be done anyway. They did the job, but now say the car won’t start and has no compression on #1. The other three cylinders have 150 to 160 PSI. It started easily and ran fine when I took it in.



IF they installed the belt wrong, is it possible to bend just a valve on #1 and not any of the others? According to the Gates timing belt guide online, it is NOT an interference engine. They say it has spark and fuel. What are the other possibilities?


#2

That’s eight valVe. I left out a “V” on vale above.


#3

Since it’s not an interference engine, even an incorrectly installed timing belt should not have caused a bent valve.

It really doesn’t matter. It ran fine when you took it in, and it should run fine when you get it back. Anything in between is the mnechanic’s responsibility to fix.


#4

I say “yes” but add that it is manufacture dependant.One tech some years ago improperly timed (valve timing) a multi-cammed BMW V-8 and only one valve got nicked (and ever so slightly also). This “nick” caused a mis-fire that was very hard to diagnoise.

One dead cylinder will not cause a no-start condition. The engine will start but run poorly. Have them oil up that dead cylinder (long shot but I am thinking cylinder is washed out) and keep looking for the cause of the no start.

I saw a "wash out cause a no start condition but the wash out product was bead blast medium not fuel. The DIYer (a friend of mine) really liked his engine paint job so when he had the heads on his small block off for overhaul he took them to another friends shop that had a bead blaster to get the old paint oof. Well he did not wash out the blast medium. That engine lasted about 2000miles before every bearing was taken out, even the cam bearings. The friend was a tree surgeon, and should have stayed in the tree.


#5

This a tough one to figure because a zero compression reading almost always points to a problem with a valve on that particular cylinder; bent, hanging open, etc.

You state the other cylinders have 150-160 PSI but those are not very good readings either. They’re not horrible yet but are heading that way and those readings could possibly be an indicator of something related to that water pump replacement.

So was this vehicle seriously overheated?
You stated that you “took” the vehicle to the shop. “Took” means you drove it and it was running fine, it was towed in or what?


#6

You remember the air cooled VW? well this is the engine type I took compression readings off the most (mandantory first step for a tune-up was a compression check). 120psi was just dandy and 90psi was where we drew the line and buttoned things up. (meaning you do not adjust valves on a customers car when the reading is 90 or below without first having a conference with the customer as when the car sucks a valve after you just adjusted the valves the customer thinks your adjustment is the cause).


#7

I agree with you about the air cooled VWs that 120 PSI is fine but once away from the air cools a 150 is not that good. The general rule of thumb is 20 X the compression ratio at sea level and shave a small amount off for altitude and barometric pressure.

Also familiar with exhaust valve stem stretch on the air cools. An overly tight exhaust valve during a lash inspection could often mean there was a catastrophic engine explosion in the future. And some people used to strongly question why the valves on an air-cooled were replaced instead of grinding them.

In the OP’s case they state it was running fine before this belt change. What I’m curious about was how it was running when it first hit the parking lot at the shop or if the engine was operated with the temp gauge in the red due to this water pump problem.

I’ve never run a compression test on one of my antique Harleys, a '44 U-Model flathead with 5:1 compression ratio and I wonder if it would even move the needle. It might be best to not even know. :slight_smile:


#8

I had a hard time believing what the mechanic told me this morning, but it was true. There were TWO notches in the cam sproket. He lined up the wrong one. He left the cover off so I could see it. The correct one had a notch as well as a raised round tit. Now it runs. I suspect it almost amounted to being about 170 degrees off on the valve timing. now why would they put two notches on that sproket?


#9

I conclude since you say “belt” and from other info. this is either the 1.3 or 1.6 engine (as opposed to the 1.8 double cam chain driven engine). I went and looked at the manual and it is hard to see how this got messed up. The manual shows one notch on the plate behind the cam sprocket and one notch on the cam AND a place to put a pin to lock the cam in place. One thing I did notice that made the view worth it was that the belt is directional (with and arrow on it) and you are instructed to maintain the original direction of travel when reinstalling the belt.Engine is listed being made by Suzuki.

I am glad all is well for you. This is just another example of the underated degree of difficulty in replacing timing belts. Based on my experience and the posts we get here these jobs are going wrong all to often, but I do realize we only hear about the jobs that went wrong.

If our readers get anything out of this post I hope it motivates them to pick the shop for this job carefully. I wonder what it feels like when you want to be picky but there is only one or two shops in town or your car is dead and you are trapped at one paticular shop.


#10

Apparently additonal info is not forthcoming but I wonder about some of this compression business. A cam out of time a tooth or two can affect the compression but I fail to see how it would cause only 1 of the 4 cylinders to be on 0.

It would still be interesting to know if this thing was overheated, towed, or whatever.


#11

Hyundais and Mitsubishis are notorious for bending valves and I have seen several of each with the valve or valves on one cylinder bent and the others OK. There is always a faint, bright indentation on the pistons of the other cylinders though. The collision is not always a bend and break catastrophe. Often the bend is too minor to see and can only be verified when liquid is poured on the inverted head and it leaks out the ports.


#12

What I don’t get is why the OP says the car now runs, although the word “runs” is not defined. I assume it runs as before.

One would think this 4 banger would run on 3 cylinders, although not very well.