I've got a 1983 240DL that runs for a week and then breaks the timing belt. It's done this twice now.

Generally reliable vehicle with 170K on it. Ran fine and then one morning it wouldn't start. Short diagnosis and...It was the timing belt.

Replaced it and the tensioner and the car just started right up. No loss of power, no ticking, runs as good as new. (made me think I had done it right!) and then, a week later, exact same thing. Car ran fine, drove it all week, drove it that day, parked it in the evening (car was warm but not "hot"), came out the next morning and it wouldn't start and the timing belt is broken.

Now I'm thinking that maybe I *DON'T* know what I'm doing or I've missed some crucial detail.

Notes:

• Replaced the tensioner the first time only. Old tensioner looked fine but I have no idea when it was last replaced (if ever) and while in there decided it was prudent.
  
• Belt *breaks*, no teeth missing, just a big tear and break in the belt.
  
• Car is driven between 100 - 120 miles between breaks.
  
• When I'm done replacing the belt, I always tighten down the tensioner adjustment nut. (this step seems incorrect to me but I've seen it mentioned in a number of guides) Seems to me the belt would stretch a bit when it is new and then slip / break if the tensioner didn't take up the slack.(??) Maybe I'm just paranoid here. I know it says to loosen the nut and then adjust and re tighten after 500 miles but I'm never getting that many miles on it.

Could it be a warm/cold cycle with the cam locking up? Should I be buying timing belts in bulk?

Thanks for any assistance!

 

try doing that loosen and retention after a dozen miles, then again at 500.

 

How does the water pump feel? Is that in the belt path on that motor?

 

The water pump is not in the path of the timing belt so that can be ruled out. The best way to determine the cause of these failures is to do a post mortem on the belt. Is it frayed all the way around the belt or has it just torn in one spot. Fraying all along would indicate rubbing against something. Perhaps posting a pic might help.

The timing belt tensioner is supposed to be loosened and re-tightened to account for the initial stretching as Pierce has mentioned. There is a little plastic plug on the timing belt cover to allow access to the nut without full disassembly of the cover.

 

If I recall there are 3 sprockets . One on the cam , one on the crank and the third is the oil pump/ distributor drive. If the tensioner is new and OK then I would look at the oil pump sprocket and see if it is the problem. Also after you replace the belt did you start it up without the belt cover on so you could see if it is tracking correctly.

 

I didn't loosen and re-tension my t-belt on my 740. Have never done it on any customers car. Never seen a t-belt break not from age.


Possible causes:
worn sprockets
crank walk
siezed or partically siezed oil pump cam
string of crap t-belt's. The t-belts your buying aren't directional?

oil or coolant leak
wrong size belt

 

Take a look at this thread:

https://volvoforums.com/forum/volvo-...-engine-24079/

There are a couple of things in here that may be causing your issue. For one it mentions two types of belts. Check to make sure you have the right one. Also it ends up being an issue with the tensioner.

 

First off, WOW! Thanks for all the awesome responses.

When I posted this I hadn't pulled the timing cover off after the most recent breakage and didn't get a chance to until last night. I figured I would go in with all the new information that had been posted here.

I should explain, it's not my car but my 17 year old sons.

What I found this time was that the belt was intact still but not moving when trying to turn the engine over. It had sheared off all the teeth around the crank shaft (which was spinning) and was just slowly melting through the belt.

Upon further questioning my son, he *may* (his words) have spent much longer than he had mentioned before sitting there and cranking the starter with the engine not turning over and including having a buddy jump the car because he thought it was the battery (ugh!). That explains the lack of shrapnel and the apparent clean break on the belt during the last two breaks. I think the just melted through the old belt and disintegrated the teeth from that broken area into dust.

In previous changes of the timing belt I had always noticed that the very first time I put a 17mm socket on the end of the cam to turn it to line it up with the notch in the top, it was always very stuff. I assumed it was compression in the motor somewhere (??). Looking back on this now, it should have concerned me more than it did.

I believe I mentioned before that it never broke a belt while running, just apparently after it sat over night which I thought was odd. I always think of "timing belts breaking" as a stranded by the roadside and call a tow truck kind of thing.

Now what I'm thinking is he drove the car (hot), parked it and let it cool down over night, the bearings seized up just enough to not easily turn and then the next morning he ground the living daylights out of the starter until the belt broke.

The result is now the cam won't turn at all. I pulled the valve cover and everything looks well oiled and nothing broken, no large metal chunks lying around or anything. I've never replaced the cam on one of these before and I'm wondering...

Two questions:

1) Is it worth it? Is a new motor cheaper? Can they be found? 176K on the existing engine.

2) If it is worth it, would it make more sense to pull the head and have the head serviced, valves reground / replaced, cam replaced ? I kind of feel that this might alleviate having to tear back into this part in the near future. Is this something that can reasonably done at home or is having the head serviced require a shop to do it? I've always taken the entire head off to someone else and said (in my best neanderthal voice), "You fix for me please!"

Thanks again.

 

you pretty much have to take the head to a machine shop.

I do believe I'd take the valve cover off, and try and ascertain whats fubar, why its not turning easily. maybe there's a broken valve spring or something.

if anything is actually broken, find a new head at a pick-n-pull. you can use the head off ANY B230F engine from a 240, 740, 940 from about 1985 forwards. the turbo engines have a different cam (and better cooled valves). the 740/940 have the distributor on the back end of the camshaft, but you can take it off and replace it with the cap/plug from your 240, and its otherwise identical.

send that 'new' head to the machine shop to be checked, surfaced, then install with a new head gasket. I'd suggest replacing all the coolant and heater hoses while you're at it, if they aren't already nearly new.

 

Today I visited my daughter whose 91 240 would not start. Sure enough when I checked to see if the cam turned when cranking, it did not. Knowing that I replaced the timing belt just 12k miles ago, I knew there was something else wrong. Sure enough, the cam was stiff as could be. I was able to loosen it up and get it running but found that it had a blown head gasket as well.

From information from my daughter (and her boyfriend), I found that the car had been overheated twice. So I agree with your assessment that the root cause is overheating causing the bearings to seize after cooling off. I checked her oil and there is no water in the oil so I am betting that the bottom end of the engine is ok. Not sure how the pistons are as the engine sounded a little "rattley" when it started. May have some piston slap. I have another head that I am going to send to the machinist to get cleaned up. THen I'll swap them and see where I get.

Thought this may be of interest to you as the symptoms match up with what you have experienced as well. It will take some time but I'll let you know how it comes out.

 

if the head gasket is fried, they are going to be rattley.

blown headgasket on a 1991 940SE turbo.



head was cracked (not evident in this picture, but #3 there was cracked between the valves and to the plug).


exhaust header was cracked too.

I scored a new head off someone on this forum, he had it in his shop ready for a project he'd changed and done different. bottom end was just fine. couple italian tuneups to burn the carbon off those pistons and that wagon was bombing down the road again. this was my kid's car. Took him and his friends on many adventures.

 

If the rattling is due to the head gasket failure, it makes me feel a little better. I was debating whether it was worth it to try to fix all the time worrying there may be further damage.

Since I have the spare head, I think I'll give it a shot at prepping it and giving the car another shot.

 

Thanks act1292. I have the valve cover removed but haven't yet had a chance to pull the cam. I'm hoping to get around to it this weekend.

I can't seem to find too much information on how the cam goes together. It looks like there are no bearings, just aluminum guides (??). I've heard that they can score and cause the cam to be tight but potentially can be polished out and made to work again. (again with the ???)

I'll post more when I know more after this weekend.

 

i'd be willing to bet either you put the harmonic balance washers on facing in instead of out, and they are being eaten. Othewise