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Jazzerpet · Joined: 07 Apr 2003 Posts: 186 Location: Omaha, NE.

What happens when the balance shaft belt breaks?

Just picked it up, Owner only had it a few days and did not know the history. It was partially taken apart but I found a busted balance shaft belt under the hood. I suspect it is the reason it was parked in 2000.

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1980 931
1985 ½ 944
Member of the “Omaha Crew”

Llamaguy · Joined: 02 Jul 2003 Posts: 711 Location: Indiana

the belt usually breaks and then causes the timing belt to break, resulting in the valves be smashed to pieces.

Where did they park it, under an advertisment bilboard?!?!
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1987 924S Guards Red
1997 Suzuki Tl1000 Supersport

Jazzerpet · Joined: 07 Apr 2003 Posts: 186 Location: Omaha, NE.

No the timing belt was ok and still in the car. The cam cover was removed. All the valves seem to be ok (the tops are all the same height across the head). If some of them were bent wouldn’t they sit lower on the top?
I bought the car only for the interior and the front valance, but it looks too nice to junk. I am just trying to find out if it is worth the time to try and make it run.
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1980 931
1985 ½ 944
Member of the “Omaha Crew”

jpab924 · Posted: Thu Sep 23, 2004 12:32 pm Post subject:

From what I`m used to working on, if the bal. shaft belt broke the oil pump would not run since it runs on the same belt. As I understand it, the shaft runs parallel to the crank and is counter-weighted to reduce the rocking motion that some engines produce...in other words, it smooths out the engine.

I`ve never seen just the bal. shaft belt break...its always the other way around. If the 2.5 b.s belt runs the oil pump, there are 2 scenarios that may have happened. The p.o. may have run it without any oil press. for a prolonged period of time, or they noticed the oil press. light came on and shut it off immediately. Hard to say. Drain the oil and look for foreign material.

My speculation depends on wether the bs belt and oil pump belt are the same.

Khal · Posted: Thu Sep 23, 2004 1:24 pm Post subject:

If you only want the interior, can I have the wheels!

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'80 924 Turbo

Paul · Posted: Thu Sep 23, 2004 1:42 pm Post subject:

The balance shaft belt only drives the balance shafts, so you may be OK.

Or the PO has already replaced the timing belt only to find the car had bent valves.

When the balance shaft belt breaks, the motor runs very rough, maybe that was enough for the PO to park it.

Paul · Posted: Thu Sep 23, 2004 1:53 pm Post subject:

Since the cam box is off, I would do a blow down check on each cylinder without any concern to what position each piston is in. Just pump in the air and let the piston go to bottom dead center, then check for air at the air filter, the radiator expansion tank, the oil fill pipe, and the tail pipe.

Just make sure the car is NOT in gear. You may want to squirt a very small amount of oil in each cylinder. Whatever you do, don't over do the oil, since it won't compress

Sleykin · Posted: Thu Sep 23, 2004 2:17 pm Post subject:

And be careful with the "valve cover" ... it has the cam and lifters in it and the lifters will fall out rather easily. The oil pump is driven by the crankshaft. The crank pully actually drives it with friction from the 150 lb/ft of torque on the crank bolt.
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Glenn Neff
Medford, OR
87' 924S

Lizard · Posted: Thu Sep 23, 2004 3:01 pm Post subject:

ok I did Rorals timing belt and when we opened it up his balance shaft belt was broken, it didnt cause any damage and upon putting it back together it runs fine.
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3 928s,

timstar92404 · Joined: 22 Sep 2004 Posts: 2075 Location: richmond BC

thats a nice 944, i think i'm going to get a 85.5+ 944 by next year i like the interior so much better. I am going to get my car repainted soon and other shit fixed (my 924) because i will drive it for a year or more and if i want to sell it i can't sell it with crappy paint or else i won't get much. After paint and fixing things i'm thinkign of selling it for 2500 don't know if someone will pay that much for a 78 924. i paid 2 grand with lots of problems on it but i don't think most people would.
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78 924 sold.
85.5 944

Jazzerpet · Joined: 07 Apr 2003 Posts: 186 Location: Omaha, NE.

It sounds like it is at least worth it to dig a little deeper. I will start with the blow down. It looks like the p.o. may have lost a few of the lifters I found most of them sitting around the engine bay. The rest may be there also. I done the belt and seal replacement on my 85.5 so that part doesn’t intimidate me any longer. I will have to get the 77 back together and out of the garage so I can get this one in.

Khal, You like those wheels? I don’t even know what type they are. I was going to put phone dials or the flat turbo wheels on it if I keep it.
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1980 931
1985 ½ 944
Member of the “Omaha Crew”

My924gtc · Joined: 14 Aug 2004 Posts: 1362 Location: 248

Those wheels are cookie cutters if I'm not mistaken. Tough to tell from the pics.
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MJ
'81 924 2.0L T
'82 924 2.3L SC/EFI <---online fall '06

Sponsor of the 944 Cup and Super Cup
Sponsor of the "2006 Battle in the Badlands"

Lizard · Posted: Fri Sep 24, 2004 6:42 am Post subject:

correct they are cookie cutters, one of the heaviest rims
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3 928s,

Jazzerpet · Joined: 07 Apr 2003 Posts: 186 Location: Omaha, NE.

Ok update, I put air to each cylinder. Air was escaping from cylinders #1,3,and 4 through the exhaust. Cylinder #2 air escaped from the intake. By popping the top of the valve with a rubber mallet the pressure that was escaping dropped. I was running air through it off my compressor. I set it at 65 lbs and the pressure would drop to 60 lbs wile it was connected. So what does this tell me?
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1980 931
1985 ½ 944
Member of the “Omaha Crew”

Paul · Posted: Mon Sep 27, 2004 11:20 am Post subject:

If the cam box is off, the valves have to be closed, so it sounds as if there are 3 bent exhaust valves and 1 bent intake valve.