AJ AJ

Hi, I'm new to Rennlist - although I've read a lot of the forum posts over the last few months. I Live in New Zealand and recently bought a 92 968 coupe - totally standard. It had a lot of work done 6 thousand miles back (but 8 years ago) including belts, seals and 'rebuilt water pump' I picked up the car 4 weeks back and drove it 700 miles back to where I live - no issues. Yesterday there a a waff of smoke from the engine - I couldn't fine anything at all, and it was running fine - I figured that a drop of something touched the exhaust. I drove 4 more miles and the temperature shot up and I could smell burning plastic.


I immediately shut the engine down and called the tow truck. I could see the end of the water pump pulley had melted through the plastic cam belt cover. I took the cover off last night to have a look. The cam belt would have been in fine condition prior to this, now it has small nicks in it and is obviously going in the bin. There's no leaks or anything that I can see. all really clean. I think that if i'd done one more mile the belt would have definitely have snapped.


I can turn the water pump spindle freely by hand - I'd have thought that the bearings would have seized and caused the problem - but oddly they seem OK at this point.


I've ordered new belts and a pump and belt cover. The rollers are like new. I'm going to have a go at fixing this as i'd like to learn those skills on this car. (I've done a lot of meachanics in the past with other cars - this doesn't appear to be too complex a job).


Is there anything that I should be looking at doing when I doing this job - I've not heard of this problem before. I'm just hoping also that the belt didn't slip at all. I've no reason to think that it did as the engine would have stopped on it's own i'd imagine.


As you can imagine - the wife isn't happy. She got the dog and I got the car. To be fair the dog did sh*t on the new rug last week - so i'd say we're almost even.


Any help would be greatly appreciated.


Cheers.

thomasmryan

The hydrolic tensioner might ha saved the valves but that is an interesting failure mode.

AJ AJ

Is there any way to tell if there's any damage to the valves and pistons - besides pulling the head? It was running ok when i turned it off - I suppose i could see if the belt has slipped by seeing if the cam shaft is aligned when piston 1 is at TDC?

The belt is of course really loose now - is was tighter yesterday when i took the cover off. it's still tight where is goes over the water pump.

AJ AJ

Here's where the pulley is sitting when #1 cylinder is at TDC. Also there's a chunk of alloy missing on the third distributor bolt. It looks like helecoils on the other 2!

spanky

Welcome to RL.
You look to be off by 2 belt cogs fro being at true cam TDC.
You can do a leak down test on each cylinder and this may give you a indication if there are bent valves,

AJ AJ

Hmm - it gets more worrying - now i am 4 teeth off (clockwise from mark). it hasn't slipped again - maybe a lack of tension the first measurement. I've been turning it by hand with a socket - i can't hear anything untoward or feel anything strange.

I've got a compression gauge but not leak down tester. Worth doing before i replace the water pump and belts though. I'd have thought the valves would be bent out of shape if it actually is 4 notches off - but it was running right up until i turned it off - no misfiring or anything strange.

AJ AJ

Just thinking - the absence of the water pump pulley would allow the cam to rotate clockwise - that would throw it out quite a bit in relation to the crank. Now it's off by so much though, you'd have though that the valves would be touching the pistons?

Charlie

I would put a new pump and belt on. Set the timing and rotate the engine by hand. If that goes OK then I would do a compression test.

RajDatta

You should time tdc using the flywheel marks and see where you stand. I would try to avoid turning the engine too much. Lack of pulley is making your timing go out a bit, but still within range where you should be ok. Be extremely careful, remove the plugs to make it easier to turn engine.

I would remove all the cover. Since you will need to do a new waterpump, you need to remove the rear belt covers. Might be a good time to check for any leaks in the balance shaft section or the crank pulley section.

You should also consider freshening the cam chain and tensioner pads unless it was already addressed.

We are here to help. No need to panic. Good luck.

thomasmryan

I would say the impeller pooped out and a piece locked the pump momentarily.

A walk through by Jürgen.
I hate giving advise but...

Buy your wife something from Tiffany's before you start buying parts)))

Take a little Emory cloth to the rotor button. It looks a little green.

spanky

If you can borrow a flexible inspection scope equipped with a light on its tip from a friend and remove the plug, rotate the piston to its lowest position and look in on top of the piston, with the engine running if a valve made even light contact you will see a fresh impact mark on the crown of this piston.
Upon 2nd thought check all 4 pistons for marks, no reason not to just to be sure. 4 valves per cylinder, will leave a mark if your belt skipped

AJ AJ

Thanks guys - I think that you're right Thomasmryan - i'll find out when I've stripped the pump I guess. I put the pump pulley back on, but the timing is showing quite a way off. The engine turns by hand easily enough - I can't see much through the plug holes - just some carbon - but nothing like valve marks. I've ordered a cheap USB camera that plugs into a lap top - so I can have a look inside. I've also ordered a leak down test meter. I really don't want to be pulling the head.


Given that the car was running fine prior to turning is off i'm keeping optimistic. And you're right - I definitely need a new dizzy cap too - looks like it had been on the car since new! New plugs were put in though - it looks like someone cut corners somewhere.

AJ AJ

Quick newby question - what powers the hydraulic tensioner? and does that stop being under tension when the engine is off?

thomasmryan

The tensioner is unique to the 968 and keeps the belt under constant tension as the engine expands.

You need to protect the bottom when compressing it in a vise. Most use the crank washer. Subaru recommends keeping their tensioners upright when compressing.

AJ AJ

Thanks - I''ve not found too much online on the 968 belt replacement. I need to find out how to make sure the balance shaft, cranks and cam all align when i'm putting the belts back on - as they're all out now - as i'm sure that it has slipped. I was wondering if it's only shown as slipped now as the tensioner took up the slack with the engine running and it now it's out. What is curious to me is that if this was the case and now it's out by some margin, I shouldn't be able to turn the engine as the valves would touch the pistons and i'd be able to feel that using a wrench to turn the engine.