Volvo 960 - Broken Timing Belt

You have a Long list of basic checking and elimination to do and without knowing what you have already checked you are bound to receive too many stupid suggestions. But on the other hand your problem may be a combination of basic errors.

Is the head warped in any way?

Fire-ring order correct?

All cylinders moving, intact correctly ringed?

Compression ok?

gaskets ok?

lifters ok?

valve seating ok?

Cam shaft ok?

and much much more.

PS do you have a manual or specs?

First thing to check would be the lifters and the rest of the valve train, since that is what was broken.

My first guess would be to check spark plugs and wires but if its getting spark, perhaps its a fuel delivery problem.

Check the compression first.

Sorry Planet of the Apes; my following comments will be small consolation to you but may be helpful to others:

Don't try to fix it. Any vehicle with an engine so poorly designed that the failure of a timing belt can destroy most of the valve train (referred to as an "interference" engine) is not worth owning (IMHO).

Here's a list of pre 1998 interference engines by make:

http://www.aa1car.com/library/timing_belts_interference_engines.htm

Here's another list that mentions engine types but not much model year info:

http://www.bigbendautocenter.com/timing_belt.htm

Another way of finding if your car has an interference engine is to go on the NAPA website Home page:

http://www.napaonline.com/default.aspx

Near the top of the left column click "select a vehicle" and fill in the info. for year, make, model and click "submit". Up comes a "Shop NAPAONLINE" page and then click "engine parts..." in the "Parts" column. The next page will offer a selection something like "camshafts and timing components". Click that and the next page will ask you for "engine type". Click on that and the page you are looking for will come up with a list of available parts. An entry under any part description in that list saying "interference engine" is your tipoff. I believe NAPA gets their timing belts from Gates and those folks probably have the best knowledge of the interference engine subject across all the common car and truck brands so the NAPA info likely comes from that source.

Ed Weldon

Name one 4 stroke diesel without rotary valves that is not an interference engine.

I bet there are very few diesel engines that do not make valve to piston contact when the timing belt breaks.......I personally do not know of one......but I expect there are some somewhere!!!

A broken timing belt is usually due to a lack of proper maintenance.......if it broke sonner than it should, there might be a case for a claim against the manufacturer.....

if it broke sonner than it should, there might be a case for a claim against the manufacturer.....

Although I like the people at Volvo, I'd have to say that the recommended 20,000 mile change intervals are pretty awful. If I bought one of these, I would press hard to have Volvo cover 3 out of 4 timing belt replacements (given that 80,000 miles is a reasonable expectation), unless it was made crystal clear at the time of sale that the intervals are so short.

Certainly in Europe, Volvos have much longer intervals between replacements.....I can find out exact details if you wish, I'll phone the dealersip and simply ask. Nobody here would accept that short distance!!!

Its also a "heads up" for anyone else, check about such intervals before purchase!!!

Were we discussing diesel engines?

It would seem to suggest the cylinder pressures are far below the 600 PSI expected??

See Bwire's post #23 for details. I think both euro spec 960s and US spec ones were affected.

You will find this article very interesting:

The '92 timing belt should have been changed at 20k miles and again at 40k miles. At that time a modification should have been done under warranty. This extends belt life another 10k miles, so the next belt change should be done at 70k miles then every 30k after that.

The 92's had an interval of 20K. Volvo developed a damper assembly that fits onto exhaust cam that was retrofitted to 92's (if it was being taken to a dealer AND the technical service bulletin was performed) and was factory-fitted to 93's that allowed the 21mm wide belt to last 30K due to less cyclic loading on belt. You can see the damper if is installed by looking through the holes in the cam gear on exhaust cam. The damper will make seeing the aluminum head through these holes difficult, especially if you compare to the intake cam pulley which is the same part but will have no damper fitted. The 94's have a revised damper and some belt driven pulleys revised and a 23mm wide belt is used (belt is different length than 21mm belt) to give a 50K interval. The 95-98 engines got a complete re-do of the belt drive and use a 28mm belt to give a 70K interval.

Here are a few hints if you are inclined to do this yourself.
Start by removing the electric fan. Take out the two screws and then pull the wiring loom connectors from the shroud. Then you can just put the fan on top of the overflow reservoir/ac dryer and you don't have to take the battery out etc.
Remove the acc belt (I use a 3/4 in adapter on my 1/2 drive breaker bar). Take off front cover. I changed the plugs at the same time so I left the plugs out so it is easier to turn the crankshaft pulley to align the timing marks on the cam pulleys. I used either an 1 and 1/4 socket to turn the crank. The notch on the crankshaft pulley is hard to find. You have to look straight down; its on the back side hub of the pulley. The matching mark is on the back of the plastic timing belt cover (which is not removed). Get them all lined up, then remove the top bolt from the belt tensioner. Then back out the bottom bolt about 1/4 to 1/2 inch. Then you can twist the tensioner which will pop the plunger from its position. Then you can take it off and remove the belt (there is a metal guard held on by two bolt behind the crankshaft pulley that must be removed from under the car).

Did you replace the valve springs or do a spring height check prior to assembly?

Did you have the cam magna-fluxed?

Was the cylinder head checked for cracks and was the head milled?

What marks were the cam set to? And what was the status of piston #1 when the cam was aligned to marks?

Did you replace anything besides the valves? If the timing belt went, it probably took more than just the valves with it. I would check for:

Busted pistons and Bent rods. And most likely the Crank needs burnishing.

It may be better to replace the engine or rebuild it.

Typically on a zero interference engine when the timing belt breaks you might do more then damage valves. I would do a compression check. You possibly could have a cracked piston. With a zero clearance engine if the timing belt breaks the engine is then out of sequence, the result is valves open when the piston strokes up during the compression stroke. The resulting crash will bend a valve and can crack the piston. I have repaired many Honda engines that have had the timing belt break and in all but one case one or more pistons had to be replaced. Good Luck!

I just did a timing belt on a Mazda engine (maintenance not broken).

The book showed marks on the front and back of the camshaft sprockets.

Before removing the original belt I lined up the timing marks to spec.

Only one set of marks on the cam side of the sprockets were valid.

You may have a similar situation. I found 4 sets of invalid marks on this particular Mazda engine and was scratching my head for a while before finding the correct set. I have found extra marks on other engines, just not this many.

The valve timing could be off although the timing marks were aligned.

Does the crank shaft make two revolutions for each one revolution of the cam?

If so, your timing could be off 180 degrees.

The new valves are now bent in such a case.

Assuming you did the repairs properly, the first thing I would do is check the igntion timing. When your timing belt broke, it may have affected your timing. Second thing to check is to make sure your spark plug wires are hooked up properly. If those two things are okay, the next thing would be a comression test.

GA - logical and makes good priority sense. Too bad some of the excellent advise in the prior thread were not followed! This project could wind up costing more than it had to ;-[

Hi POTA,

To make this beneficial for you, you will probably need to respond and interact a bit more quickly than you have in the other two threads on this subject.

To run correctly, your engine will need good, even compression. That is simple to check. Unless the cylinders and/or pistons and/or rings are in bad shape, an 80,000 mile engine with new, properly seated and installed valves and a head that has been thoroughly checked for flatness, cracks etc. should have roughly 150 psi on each cylinder (see the manual or talk to a Volvo mechanic for precise figure), and the compression should not vary from cylinder to cylinder by more than 10 psi from lowest to highest.

That is check number one. Obviously you have spark, and it would be unlikely that the fuel injectors on three cylinders suddenly stopped working, so first you need to check compression. If you don't have good even compression, then it is time to find out why not -- and there are checks you can make before tearing it down again.

Did you follow the factory-advised procedure in installing the head, using sealant in addition to the usual gaskets?

An error in cam timing will not cause only three cylinders fail to run. Likewise, an error in ignition timing will not cause three cylinders fail.

So what's the compression?

Also, I am assuming that you have fresh properly gapped spark plugs, and that when you say that you have spark, you've checked at each plug gap. Are you sure the wires to the ignition coils are in the right places?

I did one of these for a friend. The wires to the coils are very easy to get mixed up. You need a wiring diagram as each coil has different color wires.

The plugs for the coils are probably defective with the wires coming apart. I had to go to a scrap yard and purchase a used set in good condition. This is for the wiring harness.

http://www.alldata.com/ has good wiring diagrams.