13 replies to this topic

[HeroOfSpielburg]

Hey guys,

I've done my best at due diligence, checked car history, done a personal inspection, and taken the car for a PPI. However, I'm new to the PPI mechanic as well as Porsches, so if you could answer my few remaining doubts, I'd be much obliged. Car: '92 coupe with 60k miles.

1) A compression test indicated 14:14:14:12 on the four cylinders. The mechanic says the variation is within acceptable tolerance. Is this true? Is it indicative of work I'll need later?
2) If I hold my hand on it while driving, the stick shift tugs every so often, like a flick towards center then back to where it was before. The mechanic says this is probably a loose mount somewhere, but nothing to worry about.
3) Oil pressure when engine is hot and the car is in gear stays around 4. In neutral and idling it's between 2 and 3. Is this normal?
4) Mechanic says the rear brakes are rusty, most likely from not being driven much, and hopefully driving will wear off the rust, otherwise I'll need new pads. True?
5) Currently spark plugs are Beru and mechanic says if I buy the car I should replace with Bosch. Not sure if he's trying to generate business for himself but a quick Google search seems to agree. Not as concerned about this as the other things.

Apparently the front and rear body panels have been painted, due to rock chips or something else. No records I can find of an accident, but this is Europe and the car has been through a couple countries before landing here. Other than that little nicks here and there, a couple holes in the plastic grill near the bottom (probably rock), and the front wheel mudflap? is a little torn up on the inside, driving over more rocks I guess.

Thanks for help answering my question guys so I can put my fears to rest and make an offer.

Cheers,
D.

[flash]

should not be that big of a drop on 1 cylinder.

the stick shift should move, as you are on and off throttle. it should stay put at steady state.

oil is normal.

brakes - rust should scuff off from driving. it it doesn't, then pads and rotors will be indicated.

bosch copper plugs are fine for daily driver stuff. ngk iridiums will last longer and run better. bosch platinums will last the longest, but not perform as well.

[Bulti]

Welcome, hope it turns out well for you.

[HeroOfSpielburg]

Flash, so that big a difference means I'm on the road to having worn out valves or needing a ring job on the fourth cylinder? I did some reading afterwards and see that odd readings should be done again after getting a little oil squirted in the cylinder, just to check. I wish I had been more knowledgeable, I think the mechanic only checked once.

[flash]

first, i'd run the test again. if you get the same readings, then yes, put about a cc or two of oil in there and do it again. if it goes up, it's rings. it it doesn't, it's valves or guides.

the other thing that could be going on is that you have a lot of carbon in the other cylinders. the numbers are actually a bit high on those. so, if you cleaned out the carbon, the numbers might even out.

[Scott Collins]

my shifter always moved when I got on and off the gas - normal.

holes in the lower grill, which is plastic and probably fairly brittle, are also normal. I had numerous holes before I replaced the lower grill with one from Design One Racing. I did this after about 90k miles. These are unfortunately no longer available (NLA).

rotors, pads, and plugs are all relatively inexpensive. Changing spark plugs on the 968 is easier than any car I have ever
had.

most of the time you are looking for stuff like oil leaks, seepage around the balance shaft housings and also around where the head mates to the block.

You'll want to know a few more things: (forgive me if you have already covered these items).

1. Any pinion bearing service, problems, or even better, has it been replaced?
2. When was last timing belt/water pump replacement? Should be 3 years / 45k miles, whichever comes first.
3. Vario-cam pads and chain - original or replaced? You'll want to get those pads done if they are original.

#2, above, is an $1,800 job at a shop. Many here would recommend not driving the car if the timing belt is past the replacement interval of 3yrs/45k miles.

Best of luck with the car. I hope it passes muster in all of these areas.

Cheers!

-Scott

[Rap]

Welcome good luck in your search!

[PorscheG96]

deleted

Edited by PorscheG96, 24 August 2014 - 07:22 AM.

[HeroOfSpielburg]

Thanks for the additional input guys. There has not been a pinion bearing issue, and in listening to the car after letting off the gas at high speed, I didn't hear any whistle or screeching from the engine. Maybe it's okay still since the car only has 60k miles. The timing belt and water pump has been replaced recently, though it was done by some minor shop by a previous owner last year, and there is no receipt, only a stamp in the book. I haven't asked yet about vario cam pad and chain service. I'll ask the owner but I doubt it has because he didn't mention it as a selling point along with the other service.

I talked to the mechanic that did my PPI today and he said that indeed the fourth cylinder's compression was off by 2 kbars, but the engine ran fine when he drove it so he doesn't think it was worth worrying about now or preventing me from making the purchase. I don't know how paranoid I should be and insist on a redo and a leakdown test. :\

[Rap]

Patience is a virtue and due diligence well worth it.

[Scott Collins]

We can't reasonably expect a car of this age, 22+ years, to have perfect compression. I would suggest a 2nd test, if only to know where you stand at purchase.

The vario-cam pads become brittle and pitted over time and can fail. Porsche does not specify a replacement interval, but my recommendation is to replace them along with the
chain. No need to inspect them and it's a relatively easy job for a trained mechanic. I think I paid $250 plus parts, which were about $50.

Here's a DIY on the vario-cam inspection:

 variocam inspect.pdf   988.9KB   7 downloads

Edited by Scott Collins, 25 August 2014 - 10:38 AM.

[Rap]

Anyone now of a good 968 mechanic in Charleston, SC who could do a PPI?

[94SilverCab]

Reach out to BanditSC here...he lives in Charleston and is very tied in to the Porsche community...

 

Regards,

 

Jay

[Rap]

Thanks Jay