Timing Belt - I am either Really Lucky Or SOL

I have been diagnosing a low vacuum situation that occurred the other day.

Short of it it.

Car would not start Friday morning as it was really cold. Got it to fire but died and I could smell Fuel so I assumed flooded motor and took the wife's car.

Saturday I did a compression test and all cylinders were at about 80.

Added oil to the cylinders and the compression came back up to about 150150.

Car starts but was really "soggy" Like it had a vacuum leak or the timing was retarded.

Today I try disconnecting all the vacuum lines and plugging all the lines holes so I have nothing connected except the AFM to the J boot to the intake. Started it and it was still running the same.

So I decided to check the timing belt. I removed the #1 plug and put a dowel in the cylinder as I turned the motor over by hand (socket on the crank)

As I was bringing the cylinder up to TDC all of a sudden the timing belt stopped moving while I was turning it over.

I looked at the timing belt by the crank and there were 5 or so teeth missing.

SO my real question is do you all think I got the valves? I guess I will have to remove the cam and then do a leak down test on the it? Anyone got any good ideas? I have a freshly rebuilt head in the shelf that I can use I just hate to have to do it as it is dam cold out and I don't have a garage at the moment.

The attached are the results from my compression test from earlier today (you can see tht they are down from the 150 I got yesterday)as you can see all cylinders are evenly down. What do you all think?

Guestimating a bit here, but I think you're just luck on this one, as you do not hear a banging from pistons hitting valves. HOWEVER, if those 5 missing teeth on the belt are the result of a valve or two hitting a piston, and stripping off the teeth--really odd--and those valve(s) are now no longer hitting the pistons, then you're SOL. You've probably thought the same.

The only real way, is, well, hope for warmer weather.

But that timing belt is really, really odd....teeth ripped off but not a broken belt.

Leak down test should tell you if a valve(s) are munched. Start there first before breaking out the mucklucks

Shot in the dark here, but did you happen to spill some kind of solvent or something on the belt that could have hardened it? Add some cold weather to a corrupted belt, and maybe it got brittle enough to shear off teeth.

Very long odds on that, I bet.

I've seen TBs with teeth yanked out of them before, and yes it usually happens at startup.

Since they are all down evenly, I'm going to say you got lucky. BTW, you don't have to remove the cam do leakdown tests etc, if you turn the engine over and check the valve clearances if they are all real close to spec you are in good shape. If you suddenly find one with, say, .050 rather than the .010 spec, uh oh. Of course you need to install a new TB and make sure the engine is properly timed before doing this.

Not unusual in the old days of square tooth timing belts to strip teeth. Newer round tooth designs do it way less- I can't recall seeing one, actually.

As to the valves, it was running soggy because it was out of time. Unless you jumped on the ratchet to crank the engine over after you noticed the stripped belt, you are fine. Look down the oil filler hole to make sure you have lube to the top end (eg:red block Volvos will stick the cam and strip the belt if you don't keep up with the oil changes), retime and put a belt on it.

I'd remove the cam and check all the journals are good and visually see if there are any valves sitting lower than the others indicating they're bent. If that all checks out I'd put it back together and try it with a new belt. The only time I've seen a timing belt strip it's teeth was a cam snapping while the engine was running, jamming and suddenly stopping the cam gear so the crank gear stripped the teeth off the belt. Makes me think there might be something trying to prevent your cam from turning.

The compression results are weird. If the valves were not sealing you shouldn't see that jump with the wet test. Maybe fuel washed the cylinders out the previous day when it was flooded causing the low compression readings?

In crease in the wet test indicates ring/cylinder problems. Leak down will tell you.

You gotta put a belt on to check it properly. Just do it- it'll be fine.

I forgot to mention that this is on my 924s.

I just got back from driving my daughter to Uconn so I had some time to think.

Plan is to put all the pistons in the middle of the boars (I just have to back up the crank about 1/4 turn) Then remove the inspection plugs on the cam tower. I can then rotate the cam with out the valves hitting the pistons. This will let me test each cylinder one at a time by rotating the cam to close each set of valves.

It all can be done with out purchasing any parts. This should tell me what is going on.

The lower compression (120 ish) I think is due to the cam having jumped a tooth and the valve train being out of time with the crank. The intake valve was closing later thus the lower compression.

Thinking about it it was running like it had a retarted cam. Because I have an EDIS ignition system on the car that is triggered from a 72-2 wheel in the cam this is also what caused my timing to be retarded as well as my vacuum to be so low. (It was pushing air back up the intake before the intake valve closed causing much lower vacuum)

Another note. Looking at the compression graphs it never goes negitive this indicates that the rings are good.

Put a new belt on it and rerun the compression test - easy as pie. Well, hard-to-make pie.

tuna55 wrote: Put a new belt on it and rerun the compression test - easy as pie. Well, hard-to-make pie.

+1 I've had the belt strip on a non-interference VW FWIW.

This is an interference motor. This is a Porsche, If you look at the valves wrong they bend.

dean1484 wrote: This is an interference motor. This is a Porsche, If you look at the valves wrong they bend.

I realize that. My point was:

A. Stripped belts of that vintage aren't THAT uncommon.

B. The fact that you have any compression at all is a good sign. As Tuna said, replace the belt and try it. You don't have much to lose at this point IMHO.

Yep, what they said. You got lucky. Just change the timing belt and go. If you had valve damage, you would have ZERO compression in at least one cylinder. Even if they BARELY make contact, it will have less than 30psi in that cylinder.

yes.. I agree... now go buy a lottery ticket

What brand timing belt? Did you see this thread about a Conti belt on Rennlist? http://forums.rennlist.com/rennforums/924-931-944-951-968-forum/616915-contitech-timing-belt-failure.html

Yiks I did not see that. I think mine is a conti. I have not taken it off yet.

If you bent any valves, they wouldn't close completely and you'd expect to see 0 or really low compression on the corresponding cylinder(s).

Well took it apart yesterday and it was a conti belt. I removed the cam tower and put a strait edge across the top of the valves and all is good. I could have probably not done this but it seemed to be the easiest and quickest way to verify the valves. I also had a small leek from the cam tower gasket as well as the cam shaft gasket at the back of the cam tower so this was a good excuse to fix those issues

Inspection of the belt found a single isolated missing tooth and further down (about 2/3 the way around the belt) it was missing two groups of 6 +/- separated by a couple teeth.

So my theory of what happened seems to hold up.

It appears that it must have lost / jumped a tooth and then when I went to crank the motor over by hand counterclockwise (opposite of how the motor runs I think) It stripped off the two groups of teeth. Thus I did not damage the motor. I will not know for sure until I get it back together but the compression tests I did and all the valves lining up seems to indicate I was very lucky.

So today continue the tear-down.

I have to get the lower cover off the front of the motor, the alternator belt off and the balance shaft belt off. Then is is just clean things up inspect the rollers (I have a complete set on the shelf if I have to replace any)

If all goes well I may be running by tonight. The biggest problem is the cold. The cold seems to make the "good enough threshold" much lower. I have learned that if I am thinking good enough I have to go inside and have a cup of coffee and see if it is good enough when I come out.

I can / will post pix if anyone want to see my pain. .. . I mean porsche. ..

tuna55 wrote: Put a new belt on it and rerun the compression test - easy as pie. Well, hard-to-make pie.

Is there such a thing as an easy timing belt replacement? Seriously. I have done many and I can not think of a particular one that is easier than another. The late 80's escort's was fun not only do you remove the motor mount but you have to drill a hole in the frame. Then grind down a socket to get it between the frame and the pulley on the crank.

dean1484 wrote:

tuna55 wrote: Put a new belt on it and rerun the compression test - easy as pie. Well, hard-to-make pie.

Is there such a thing as an easy timing belt replacement? Seriously. I have done many and I can not think of a particular one that is easier than another. The late 80's escort's was fun not only do you remove the motor mount but you have to drill a hole in the frame. Then grind down a socket to get it between the frame and the pulley on the crank.

That's why it is hard-to-make pie!

I thought the Civic was really bad until I did the PT Cruiser.

dean1484 wrote: Is there such a thing as an easy timing belt replacement? Seriously. I have done many and I can not think of a particular one that is easier than another. The late 80's escort's was fun not only do you remove the motor mount but you have to drill a hole in the frame. Then grind down a socket to get it between the frame and the pulley on the crank.

Volvo whiteblock is pretty easy, don't even have to screw with the engine accesories other than removing the serpentine belt. To make up for this though it's almost impossible to see the timing mark on the crank.

Fiat 124 1800 can be done in about half an hour.. the hardest part is opening up the cooling systel and refilling

The ZX2 Zetec is not too bad, you have to pay attention to the VCT though.