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-   -   Do I need to drop engine? (https://rennlist.com/forums/911-forum/1124535-do-i-need-to-drop-engine.html)

No_snivelling 01-17-2019 10:12 AM

Do I need to drop engine?
 
I have recently purchased a 1992 C4 with 25,000 miles which was in storage for 15 years.

While setting the valves I did a cold leakdown test with dismal results. Although the leakdown tester indicated all cylinders to be “acceptable” (within the green zone on the gage), I do not accept these results based mainly upon the fact that I can hear leakage at the exhaust flange where the cat converter connects. Cat was removed for valve adjustment. I understand that a leakdown should be performed on a hot engine, but would a hot engine really stop a leak that can be heard in the exhaust? I figured the only way it could be leaking into the exhaust would be from a bent exhaust valve or perhaps a badly burned exhaust valve. I did the testing after I set the valves so I know the rockers were not holding a valve partly open.

Cold leakdown values ranged from 15% to 26% and cold compression values ranged from 120 to 205 psi. So before I drop this low mileage engine and dive in, is there anything I am missing that might mean I don’t need to drop the engine? This is my first Porsche and an engine drop is somewhat intimidating but I will tackle it if necessary. Thanks in advance for any help that anyone can provide. Oh and one more thing. The engine runs and to me it sounds good but with the cat removed and all the tin and blower removed I did not want to run it for long for fear of overheating.

Auto_Werks 3.6 01-17-2019 10:24 AM

Tom, if it sat for 15 years, I would definitely want to run and drive the car for a while before I made the leap to a rebuild. Engines can get gunked up from sitting and skew the results. I would want to put a few thousand miles on the car before I made that decision. Probably the first few hundred miles kind of easy, and then progressively more like an "Italian tune up". You can then recheck the leak / compression numbers and see where you stand. Obviously in the interim miles, you'll want to keep eyes open for any signs that things are going wrong, and immediate attention would be needed; IE severe oil leaks, knocking or other nefarious noises. You may also have to redo the valve adjustment depending on what the carbon deposit situation is at the moment. In all likeliness after sitting for 15 years it will have some leaks that you'll eventually want to clean up. Spending a couple thousand miles getting a feel for the condition can help you understand how comprehensive the rebuild will need to be.

Spyerx 01-17-2019 01:28 PM

Totally agree. Change oil, change plugs, ensure you don't have any dangerous oil leaks. Adjust valves. Patch it up, and go drive it. Check oil level every couple hundred miles. After 1000 or so, check the plugs. Track consumption. Adjust valves again and do another leak/compression. Give that thing an Italian tune up and let it run in a bit. This will also ensure that any real leaks are found, etc.

No_snivelling 01-18-2019 09:39 AM

Thanks Auto_Werks and Spyrex. It sounds like good advice and I will take it. This has the added benefit of allowing me to figure out what else might be wrong with the car.
For instance, I had nightmares about dropping the engine, completing a top end job and then on my first test drive discovering that the transmission needed work and then out comes the engine again.

Mark Salvetti 01-18-2019 10:54 PM

You guys with the 964's, after sitting so long, should Tom also replace the distributor drive belt?

Mark

Super90 01-18-2019 11:57 PM


Originally Posted by Mark Salvetti (Post 15576859)
You guys with the 964's, after sitting so long, should Tom also replace the distributor drive belt?

Mark

Not a bad idea.

Spyerx 01-19-2019 12:39 AM

If no record of being done it needs to be looked at. Power steering drive belt too.

No_snivelling 01-19-2019 09:16 AM

Thanks guys. I have already replaced the distributor belt and installed the vent kit. It's a good thing I did as the belt was starting to fray and there was a fair amount of rubber dust in the housings.

How do I inspect the power steering belt? Does this require major disassembly? I assume if it fails, the car can still make it home?

theiceman 01-19-2019 12:07 PM

Keep in mind this is not a 964 forum so we don't have PS.
964 has their own forum with tech advice specific to that model

Cheers

No_snivelling 01-19-2019 02:36 PM


Originally Posted by theiceman (Post 15577689)
Keep in mind this is not a 964 forum so we don't have PS.
964 has their own forum with tech advice specific to that model

Cheers

Being a Porsche newbie I had no idea other 911's don't have PS. My apologies.

aaron.finch 01-20-2019 10:24 AM

I have a 1989 carrera 4 i need to remove engine to replace starter motor is there much more i need to do other than what you have listed in you article how to remove an engine of a 911?

theiceman 01-20-2019 02:36 PM

I would go to air cooled sub forum 964 and ask this is for 911 ( up to 89)


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