924Board.org

[The Fife]

After cleaning up the car and pushing it (uphill!) into the garage this evening I poked around some under the hood to piece together everything I've been reading now with what it looks like in real life. So pretty quickly I notice the timing and balance belts since the cover is already off and the accessory belt isn't there. I had a feel of the balance belt - looks like it's in good shape. Then the timing belt which to my surprise was actually there. I thought it was just a piece of it still left but that didn't make much sense because it was tight like a belt should feel next to the water pump and again where it comes down after it goes by the head. My conclusion: unless somehow it's broken underneath the engine the car I bought with a broken timing belt doesn't actually have a broken timing belt!

So now what to do... maybe turn the engine by hand a little and watch what happens? Pull all the spark plugs, turn it carefully by hand a revolution or two, and feel for resistance (valves contacting pistons)? What size bolt is on the front of the engine? I'm used to turning engines literally by hand but I have a feeling this one will require a socket.

[gohim]

If the belt timing belt is off as little as only two teeth, the valves could be bent.

If the original problem that caused the belt to break before was mechanical, and was not repaired, it is possible that teeth were ripped from the belt, and while the belt has not broken, it does not rotate either (meanign bent valves).

Or, may be the head was not repaired properly when the timing belt damaged occurred before.

Or, may be another problem caused the engine to sieze (or otherwise stop running.

Since the damage has always been done (probably), what I would do is use a socket to rotate the crankshaft to the timing marks to see if they line up.

If the timing marks are off, then the the head has bent valves, and you need to remove the head, and take it in to have the bent valves and damaged valve guides replaced. You can not tell from rotating the engine whether there are any bent valves, and wront timing MEANS BENT VALVES.

Make sure that you take the nead to a shop experienced in 944 engine head repairs. Not a 911, 914, 924 shop. Has to be a 944 shop. Expalin what happened, and make sure that they will check all the valve guides, and not just those where they can see the obviously bent valves (gotta make sure that the damaged guides from previous problem were properly replaced).

If the engine will not rotate, it could be that elther the flywheel sensors were not properly installed, and are now contacting the flywheel, stopping the engine from turning. In this case you will need to remove the damaged flywheels sensors, buy new sensors, install the new sensors, and set the clearance.

If could also be that the crankshaft bolt was not properly torqued, and as a consequence, the oil pump drive gear (which is depends on friction from the crankshaft pulley) was slipping, and the engine was oil starved, and the block is ruined.

Another possibility if the engine is locked up happened to another poster. When his belt broke, and the pistons hit the valves, a valve head separated from the valve stem. When the loose valve head fell into the cylinder, and the piston pushed it up, it wedged against the piston, the head, and the cylinder wall. The cylinder wall cracked, and the engine block was totaled. This person's problem showed up are zero compression, when a compression check was done after the head was repaired, and reinstalled, and the engine was overheating.

[The Fife]

I'm heading out to give the engine a little turn by hand. The belt originally blew because a roller froze up. He replaced the rollers, the belt, and water pump. The head was sent out to a shop where they fixed the valves and installed new guides. I don't know exactly where, though. Everything was put back together and that's where the new belt was supposed to have snapped - while cranking the engine.

Edit: well, the timing and balance belts when I turn the engine... so I know the belt has teeth where I can see them and where it is on the crankshaft. Still know nothing about:
1) the allignment of timing marks
2) whether the belt is stipped somewhere else and it hasn't come back around/into view yet.

More answers coming as I get them.

[Sleykin]

It is a tough call to second guess what the PO did to make hime decide it was a belt. Pull the plugs and check the timing then check compression and go from there. You might just get lucky and he put the rotor on wrong and it slid out and mangled itself. Would be cool if all it needed is a new cap and rotor The water pump should be really hard to turn by hand if the belt is tensioned correctly (if you can turn it at all).
http://www.cannell.co.uk/944%20Reference.htm Has some good info on the whole car ... though it is aimed at the 944 most of it applies to the 924S.
Also http://www.clarks-garage.com/ has an excellent shop manual online with lots of good troubleshooting stuff. The BBS there is quite good too for the 944/924S.
Good Luck!
Now I get to go out and change my A/C compressor so I can be cool again
_________________
Glenn Neff
Medford, OR
87' 924S

[The Fife]

Got it at TDC - the two marks line up exactly... what the PO told me really isn't making a lot of sense anymore! Guess I'll break out the compression gauge and see what the readings tell me. The engine hasn't been run in a good year and a half or so and I'll be turning it by hand. Maybe the backfire was caused by a spark problem. The spark plugs did have a good coating of carbon on them.

[Paul]

The compression test will tell the story, hope you have normal compression!

It is not uncommon for inexperienced mechanics to try to install a new belt after a break in the faint hope that everything will be magically OK. Hope this is not the explaination in this case.

[The Fife]

It might be - I got out my compression tester and recorded 0 psi on all 4 cylinders. It can't be because the timing is off (marks line up) but maybe because it hasn't been run in a year and a half and it could use a little oil in the cylinder before testing? That's my last resort before printing out a few pages on Clark's Garage and going out to pull the head.

edit:
no compression after giving it a capful of oil down the spark plug hole. Looks like it's time to pull the head.

the silver lining: at least the accessory belts, distributer/rotor, and timing belt cover are already off.

[Joes924Racer]

On the ealr cars are so foretunate just about the worst tht
can happen is the belt is over adjusted causen a pulley failure.
though if you have no cp some-thins wrong , like could be only timing
though what the heck maybe its time for a new head-g. Valves are not
an issue sounds like ... maybe the rings have you checked the timing and adjusted or what?


_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

[Sleykin]

Are you turning it with the starter to test compression? You may not get any turning it by hand.
_________________
Glenn Neff
Medford, OR
87' 924S

[The Fife]

I turned by hand at first because the battery was dead. It wouldn't recharge so I went and got a new one, then tried testing again. No luck, still 0 psi. Then I added a capful of oil to cyl. #1 because maybe the fact that the engine was dry was affecting things. No change so I guess it's time to dive in and have a look at the head.

This evening I got the fuel rail, intake manifold, and distributer/rotor off so maybe tomorrow I'll be able to have a look at the valves. Actually I can already see the intake valves and they look alright - everything is at an angle, so I guess they could be slightly bent. Working on this car is different from what I'm used to (American cars from the '70s). It's more complicated, but then again that intake manifold that I pulled would've weighed 85lbs on my '70 F-100.

[gohim]

There is no way that you could end up with 0 compression on all cylinders.

As Sleykin wrote, are you using the starter to turn the engine? Turning by hand is not going to produce much, if any compression.

Are you sure that the timing belt is turning?

May be the key on the crankshaft pulley sheered off, and the timing belt is not turning? But it seems like you should still get compression in one or two cylinders.

Is the compression tester good?

[Sleykin]

I'm sure you at least did the thumb test first to verify the 0 pressure was for real When you pull the cam housing be aware the lifters are only held in by the oil on them. Good idea to slip a piece of cardboard or such under the cam housing before you lift it. You need a long 6mm allen wrench to get at the bolts inside the cam housing. Most 3/8" allen sockets won't fit and you stand the chance of dropping it into the cam housing. Most folk cut a long 6mm allen and put that in a socket. I just turned mine down on the lathe and taped it to the extension.
It is odd that you have no compression on all cylinders if the cam is actually turning and in proper time with the crank. Interesting to see what you find in there. Hope it is good news
_________________
Glenn Neff
Medford, OR
87' 924S

[Joes924Racer]

What ever you may be used to I dont want to try and turn
any 924 motor over by hand to get the cp up for sure I also
try to stay away from that sort of thing just hook up the cp checker and turn oiver the motr with the starter and battery you just want to check things out huh...

When I broke a water pump belt on my early na after replacing the head I had the motor lock up right after starting it stopped .. I hand turned it and got it free..it happend a couple more times ... Well the locking up smoked
the teeth off just teared em right off or at least 3/4s of the way which is almost off on the cam belt ...turned out to be a piece of the middle ring I guess from a piston..Do you believe that..that belt prob caused me a piston
turned out another 1 or 2 cyl. had broke rings that stayed in place...I just cant belive it got by the piston the cyl. were fine.. I just had the block honed about a year ago..Warpoed the cyl. head like you woudnt belive though still straightenable .. its a nice p&ped head I like its just gives more torque. Good luck and check the timing.
_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

[The Fife]

[Sleykin]

Was the distributer rotor turning? Only thing I can think of is a broken cam or a sheared/missing cam key. Please don't leave us in the dark
_________________
Glenn Neff
Medford, OR
87' 924S