jimhsu

Question on doing a compression test as part of the pre purchase inspection (PPI):

Spoke to one shop in Midwest about doing a thorough PPI for a 2001 996TT with 50K+ miles on, which I would think includes a compression test.

What this shop tells me is that doing compression on a 996TT is much more time and labor consuming than other models, including taking the rear bumper off and other components to get to do the test, and will increase the PPI cost by $275 to $300 dollars, to something approaching $600-650.

Is the "BUMPER OFF" a necessity for compression test unique to 996 Turbo cars?

Do shops generally charge additional cost for 996Turbo compression tests compared to 996C4S, etc.??

I don't mind paying for it if this is necessary, but does this seem consistent with your experience for those who have had a PPI with compression test done on a 996 Turbo??

Thanks,

Jim

BMo

Jim, I've been dealing with these very questions recently as I have been looking (and finally bought a car this past weekend). The standard PPI does not include a leakdown test but will test other, indirect parameters of compression and general mechanical integrity. Someone suggested to get a leak down since you're looking for a car with a few more miles and I think that's a very good idea (I'm no expert though). It'll cost you an extra $200 to $300 (roughly) and does involve removing the rear bumper. It's somewhat time consuming for the tech. I do think it's worth it for you to do before shelling out the $$$ however. My 2 centimos!

jimhsu

Thanks for your info.

From what I hear the bumper removal for compression test is unique to the Turbo. Is this your understanding as well?

PorschePhD

You have to pull it because you can not get to the the spark plugs if you do not. This is normal and the process is about 4-6 hours.

jimhsu

Stephen,

Thanks for your input.

Is the bumper off requirement unique to the 996TT and is not required in say a 996C4S?

I may have a 996TT for PPI at Imagine Auto.

What's the best way to get in touch with you?

You can email me at hsujim at gmail dot com.

Thanks!

Duane993

4 hours to pull the bumper...What do they use...a teaspoon

PorschePhD

And the intercoolers, inter sheilds, heat sheild, coil packs. Have you changed the plugs in a TT?Just to get a spark plug wrench in there after all that is a joke.
You can contact me at 913 310-9927.

Any of my staff can help of talk to me directly.

Kevin

BMo, which car did you get?? Did you find another car or is it the same one that you posted from the other week.

I wouldn't waste my time on just a compression test..

I'd opt for the leakdown test and REPLACE the plugs while you are in there... Bosch FR6 LDC

jimhsu

Kevin,

when you said you wouldn't do JUST a compression....

you mean you would do a leakdown AND compression AND plug replacement, or did you mean skip the compression, do a leakdown and plug replacement?

Stephen, any thoughts on leakdown vs compression?

PorschePhD

I concur.

Kevin

I'd skip the compression test.. And do the leakdown and plug replacement.

I have had my hands on a few 996TT cylinder heads, and the 4 valve head has had some porosity in the casting that leads to a cylinder head failures. The head will open up and spray/weap coolant. Corrosion will be present on the valve to seat surface, whether at the intake or exhaust and in the worst case in the combustion chamber.. A leakdown will catch a corroded seat. Due to the lack of sealing of the valve and seat. I had my hands on a customers cylinder head last week with this exact issue. I will post some pictures.

I am not trying to lead to "the sky is falling" but these cars are falling out of warranty and these engines will set you back a few bucks to repair them. I know of 4 engines that have had one head replaced since last summer.. 3 01's and 1 '02..

jimhsu

Thanks kevin, PorschePhD....

Is the bumper off steps for compression or leakdown or sparkplug replacement a necessity ONLY for the Turbo and not for the C4S?

This will alleviate my concerns that the PPIs described for C4S by some shops are not done adequately.

PorschePhD

Yes. The issue is the placement of the intercoolers. They are in the back bumper and this is the reason you can not access the sparkplugs. You must remove them and you can not achieve that without removing the bumper. The NA cars have a single plate then the coil packs are exposed. Nothing else is in the way. You also have the turbos in the way from underneath so you have to pull the intercoolers and come up and through the turbos. Again, the NA cars have nothing in the way of the packs other than 2 10mm bolts and a plate.

jimhsu

Thanks Stephen.