Zero compression 1,2,3,4

Richard Foy · 09-21-2001, 07:23 PM

Don't ever shift from 3rd gear @6K rpm into 2nd...ouch...
Anyhow, no compression any cylinder, but no holes in block, oil pan, or any oil leaks either.
During compression test, engine cranks over at normal speed, with and extra click click noise. The Timing marks are all lined up properly, camshaft and balance belts are all still good, and aligned from camshaft to crank, to flywheel. (I had put new belts on 3 months before and had paint marked everything, plus left off the belt cover so easier to see whats going on)

Big holes in pistons? Pull head? Pan?

T86951 · 09-21-2001, 07:44 PM

I would think you only have bent valves and your pistons are OK. I broke a cam belt once in my NA 944 and bent some valves and no piston damage at all. I would guess your valves floated and tapped the pistons enough to bend the valve. You will have to pull the head to find out for sure but the pistons are hard to break with the tip of a valve but could happen.
GOOD LUCK

[This message has been edited by T86951 (edited 09-21-2001).]

Richard Foy · 09-21-2001, 07:54 PM

Oh...if it only were so I'll be a happy camper...I'll pull the head tomorrow...thanks

Lawrence Coppari · 09-22-2001, 11:29 AM

Good luck. Sounds like valves to me.

TheStig · 09-22-2001, 03:02 PM

I knew a guy with a 1991 Carrera 2 that missed a shift and sucked some valves in...Richard you definitely have a bent valve somewhere in there. be luck you don't have a 911, its a ***** to get those heads off of 911s when compared to the 944.

------------------
Porsche. Es gibt keinen Ersatz.

T86951 · 09-22-2001, 05:21 PM

Hey Richard you may have ripped the timing belt apart or shreaded teeth off of it, it has to come off anyway but I would put a new belt on it even if it looks OK, If you are going to reuse the balance shaft belt mark the direction so you can put it back that way.

Dave951 · Dave951's Garage

The add to the last post, you won't even need to take the balance shaft belt off if you are just pulling the head. However, if I knew the balance shaft belt had gone through a massive acceleration (like from 6000 to 8 or 9K very quickly), I would replace it anyways. Having the balance shaft belt break isn't so bad by itself, as these cars can run pretty smoothly without it. However, chances that the broken balance belt will get caught and destroy your timing belt are pretty high. Replace both to be safe.

Good luck,
Dave

Richard Foy · 09-23-2001, 05:44 PM

I pulled the expected things:
The air filter assembly, throttle cable, speed control cable, injectors, injector connectors, distrib. cover, marked camshaft pully, cameshaft belt (looks ok, it bardly had 4,000 miles on it..will replace), fuel lines, fuel manifold, plug wires, plugs, camshaft cover, and intake manifold. Now ready for the head on Monday.

Questions:
I found a nearly torn off support bracket on the fuel injector manifold. The bracket is one that holds the main fuel into the fuel pressure regulator. I think the last person to remove the fuel line, did it pulling only on the fuel line 'b-nut' and nearly tore off the bracket in the process...
Can this bracket be welded?
Is it brass, or brass covered steel?
I looked into the intake holes, and the vales are not obviously broken, but hard to tell.
When I get the head off, I would it will be obvious as to which valve(s) are bad.
What is the best way to check all of them?
I'm pretty sure my idle control value has been bad, and now can I pull it apart and check/fix it?

All, Thanks for help!

T86951 · 09-23-2001, 05:52 PM

What year is your car? If it is an 85.5 or newer I can tell you how to check your idle control valve.

Richard Foy · 09-24-2001, 04:47 AM

85.5na ...I'm not sure if the name is idle control valve,,or bypass valve..it's the one under the intake manifold

T86951 · 09-24-2001, 06:41 AM

Idle control valve is what its called.
The idle control valve on my car ('86 na same as a 85.5) has 3 posts. On a cold start voltage is suppost to be supplied to the center and top posts which opens the valve to let extra air in to help it idle when cold. As the car warms up power is suppost to be shifted from the top post to the center and bottom posts which closes the valve.
To test the valve unplug the connector and run 2 wires from my battery and touch the positive to the center and negitive to the top post and the valve opens. keeping the positive on the center post touch the negitive to the bottom post and the valve should close. Do it back and forth a couple times to make sure it is opening and closing. This is just an electric motor that opens the valve and closes the valve. Filtered air is all that goes thru the valve so it should not be gummed up. My NA 944 has 203,000 miles on it and its clean inside.

Richard Foy · 09-24-2001, 12:10 PM

I Pulled the head today, and it appears that only the exaust valves 4,3,2 are bent. They are 'clean' from the impact, on 1/2 of the each valve, and you can see a shinny cresent in the top of each pistion on the the ehaust side, but not the intake side. Each exhaust valve is not retracted into the valve seat and I can see daylight between.
The pistons seem ok, so now I guess I start trying to put it all back together.....

I was surprized at how loose the exhaust header-to-head nuts were. 20ft lbs? I guess the heat there must be more than enought to tighten things up.

I'm much more in aw (sp) at all of you out there that have done this, and got it to run afterwards. Anyone who has should have a tee-shirt or a Super-bowl kind of ring telling about it.

I expect it will take 2,3 times as long to fix it an put it all back toghter again, without having more problems than I started out with.

Mrmerlin · 09-24-2001, 06:17 PM

Stan Kolen[QUOTE]Originally posted by
Hi I was wondering if you found out what the cause of the failure was?
It seems that if all was in good condition then you would not have done any engine damage, i am wondering if maybe the timing belt was a tooth off to begin with, or was it loose? this might explain the piston contact, just some food for thought.....Stan

T86951 · 09-24-2001, 08:13 PM

what about # 1, you said no compression on 1234 . Check 1 again cause u must have a bent valve there also if you had no compression there.

Going from 6000 in 3rd gear to 2nd gear would mechanically increase the revs to about 8000 and float the valves hitting the pistons.

Richard Foy · 09-25-2001, 12:28 PM

Yes, it was all four exhause valves were bent...my guess it's because the exhaust valves are about 1/4 inch longer then the intake valves.
I checked my idle control valve, and I think its messed up...seems like with no voltage applied, the valve should be closed. But I can easily move stuff around inside it with a screwdriver, an blow thru (yuckk) it.
The resistance and between the outisde two posts reads about 65 ohms, with no other resistance readings from center to outside. That doesn't seem right..will research it a bit more. And will try the test on it that T86951 suggested.
BTW it is coal black inside the airway.

T86951 · 09-25-2001, 12:36 PM

If voltage is applied the the ICV in the direction to open it it will stay open til voltage is applied the other direction to close it or visa versa. it isn't spring loaded to stay closed if it has no volage to it. Alternate the voltage back and forth , if it opens and then closes and opens back as you change the voltage to the posts it should be ok.
Sorry about your valves, I broke a cam belt once and bent valves, bummer!

[This message has been edited by T86951 (edited 09-25-2001).]