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Engine Compression and Leakdown Tests

Jcx

Well-known member
Joined
15 Aug 2013
Messages
3,876
Hi All,

I've had my car in for a major service this week and I asked the garage to do a compression test and a leakdown test so that I could have a better understanding where the 63K mile engine is on the "Oh its a 964? Rebuilt the engine yet? Throw it away then!" curve.

So, i'll post results when i get them but until then, for a bit of fun, where would the numbers have to fall to make you:

A). leap for joy as you have a great engine
B). thank your lucky stars for years of rebuild-free motoring
C). start saving for a rebuild in the next 10-20k miles
D). start crying at the thought of rebuilding next year
E). start praying for a lottery win this year
F). start drafting the for sale ad tonight

Specifically i am looking for PSI numbers for the compression tests and leakdown % for each cylinder.

i.e.

A). leap for joy as you have a great engine - 220PSI & 5% loss
B). thank your lucky stars for years of rebuild-free motoring - 200PSI & 10% loss
C). start saving for a rebuild in the next 10-20k miles - 180PSI & 15% loss
D). start crying at the thought of rebuilding next year - 140PSI & 25% loss
E). start praying for a lottery win this year - 120PSI & 35% loss
F). start drafting the for sale ad tonight - 100PSI & 45% loss
 
Wow no one wants to play?! I bet when I post my numbers I'll have enough opinions and/or doom to re-turf Twickenham.

Or are you all being kind, expecting the worst and not wanting to see a grown man cry?

Come on folks, it's Friday, have some fun. What kind of numbers can I be happy with? Car has 63k miles and is a 964 so some will claim that it needs a rebuild and the numbers will prove it. Is that you?
 
What happens if you get good compression and strange leakdown numbers...they are not directly correlated as your choices suggest. In fact if they were consistent on any of those choices the motor would likely be fine. Large differences on one or two cylinders is an indication something may be worn but oil use is probably the best gauge of when the motor needs work imo.
 
ras62 said:
What happens if you get good compression and strange leakdown numbers...they are not directly correlated as your choices suggest. In fact if they were consistent on any of those choices the motor would likely be fine. Large differences on one or two cylinders is an indication something may be worn but oil use is probably the best gauge of when the motor needs work imo.

Thx Rob, that's exactly what i had learned in the research i had done. I was just throwing some numbers up to get the fun started. The car pulls strongly so i expect good results but FUD gave me cause to have it checked.
 
Obviously engines need a rebuild when something fails but thankfully that is fairly rare. Headstud breakage springs to mind as a good example. Apart from this they just wear out usually exhaust valve guides first. This can be checked when the valves are being gapped or better still when the exhaust headers are removed and you can see how much oil is on the valve. Truth is these engines can go for years even when they are worn :thumb:
 
ras62 said:
Obviously engines need a rebuild when something fails but thankfully that is fairly rare. Headstud breakage springs to mind as a good example. Apart from this they just wear out usually exhaust valve guides first. This can be checked when the valves are being gapped or better still when the exhaust headers are removed and you can see how much oil is on the valve. Truth is these engines can go for years even when they are worn :thumb:

Nice bit of (not so common) common sense.

I will find out later today when i (hope to) collect the car.
 
Jcx said:
Hi All,

I've had my car in for a major service this week and I asked the garage to do a compression test and a leakdown test so that I could have a better understanding where the 63K mile engine is on the "Oh its a 964? Rebuilt the engine yet? Throw it away then!" curve.

So, i'll post results when i get them but until then, for a bit of fun, where would the numbers have to fall to make you:

A). leap for joy as you have a great engine
B). thank your lucky stars for years of rebuild-free motoring
C). start saving for a rebuild in the next 10-20k miles
D). start crying at the thought of rebuilding next year
E). start praying for a lottery win this year
F). start drafting the for sale ad tonight

Specifically i am looking for PSI numbers for the compression tests and leakdown % for each cylinder.

i.e.

A). leap for joy as you have a great engine - 220PSI & 5% loss
B). thank your lucky stars for years of rebuild-free motoring - 200PSI & 10% loss
C). start saving for a rebuild in the next 10-20k miles - 180PSI & 15% loss
D). start crying at the thought of rebuilding next year - 140PSI & 25% loss
E). start praying for a lottery win this year - 120PSI & 35% loss
F). start drafting the for sale ad tonight - 100PSI & 45% loss

Composing my analysis but one is hoping that german engineering would result in something no worse than option C but it should be option B, allowing for 25 years of life ? :dont know:
 
If all else is good, as in no smoking and engine pulls strong then 25 on a couple of cyclinders will still give you another 10k.
 
Joe,
This is Ouija Board stuff :eek: you never know what compression is gonna contact you....You don't know what your messing with here :puh:
 
Chief said:
Joe,
This is Ouija Board stuff :eek: you never know what compression is gonna contact you....You don't know what your messing with here :puh:

Chief I am the kid that watched Candyman and then went straight upstairs to look in the mirror and say Candyman Candyman Candyman.

And I'm still typi...
 
Joe, joe come back! where have you disappeared to......... :eek:
Oh, well there's always one. It's like on Startrek when one of the crew wore a red uniform you knew they were for it :grin:

Shame, only met him once. Real nice chap :dont know:
 
Chief said:
Joe, joe come back! where have you disappeared to......... :eek:
Oh, well there's always one. It's like on Startrek when one of the crew wore a red uniform you knew they were for it :grin:

Shame, only met him once. Real nice chap :dont know:

...ng. Phew that was close. :)
 
Rossi911 said:
Jcx said:
Hi All,

I've had my car in for a major service this week and I asked the garage to do a compression test and a leakdown test so that I could have a better understanding where the 63K mile engine is on the "Oh its a 964? Rebuilt the engine yet? Throw it away then!" curve.

So, i'll post results when i get them but until then, for a bit of fun, where would the numbers have to fall to make you:

A). leap for joy as you have a great engine
B). thank your lucky stars for years of rebuild-free motoring
C). start saving for a rebuild in the next 10-20k miles
D). start crying at the thought of rebuilding next year
E). start praying for a lottery win this year
F). start drafting the for sale ad tonight

Specifically i am looking for PSI numbers for the compression tests and leakdown % for each cylinder.

i.e.

A). leap for joy as you have a great engine - 220PSI & 5% loss
B). thank your lucky stars for years of rebuild-free motoring - 200PSI & 10% loss
C). start saving for a rebuild in the next 10-20k miles - 180PSI & 15% loss
D). start crying at the thought of rebuilding next year - 140PSI & 25% loss
E). start praying for a lottery win this year - 120PSI & 35% loss
F). start drafting the for sale ad tonight - 100PSI & 45% loss

Composing my analysis but one is hoping that german engineering would result in something no worse than option C but it should be option B, allowing for 25 years of life ? :dont know:

Brave Rossi! Bravo!!

The answer is B). thank your lucky stars for years of rebuild-free motoring - 200PSI & 10% loss

My actual numbers for compression and leak down were very tightly grouped showing good health and even wear.

Compression registered ~200PSI with only one cylinder registering <200PSI at 198PSI and the highest reading 205PSI. Giving a very tightly grouped 3.4% variation from highest to lowest.

For leak down the numbers ranged from 8% to 9% with a very even 3@8% and 3@9%.

I had a major service on the same visit which included a dizzy strip and service, new dizzy belt, new dizzy caps, new dizzy rotors. new cam cover seals top and bottom along with new plugs. brake fluid. new fan belts. fuel and air filters. etc. Car fires up instantly on the first turn of the key and is raring to go. Great service and attention to detail by Dove House. No wonder they are the 911.UK service garage award holders.
 
That's great news Jo. You can sleep easier now.
I can't recal what mine were, but remember there weren't that good.
To be fare, mine was suffering with lack of use, so I should re-test :?:
 
Chief said:
That's great news Jo. You can sleep easier now.
I can't recal what mine were, but remember there weren't that good.
To be fare, mine was suffering with lack of use, so I should re-test :?:

I am thrilled Mark. I was concerned, if only because of the FUD spread on the web about 964s and engine rebuilds, but nevertheless concerned.

I got so lucky with my purchase as I really didn't know much when I started looking... And I learned more as I progressed.
 

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