Inconsistent Compression Test Results

[PewPew]

Hey guys. I was looking to buy my first Skyline, did my homework, looked around and ended up pretty happy with this R34 GTT. Picked up the bank cheque this morning, spent 1.5k on some fresh rubber and some stockies as he wanted to keep the rims, sorted out all the insurance, even had the transfer of ownership forms filled out and ready to be signed.

Did an inspection and compression test as a last thing this afternoon. Everything was looking good, no accident damage, no rust. Just needed new tyres, new brake pads..stuff like that. And then... compression test results:

160

150

105

155

100

110

It was totally unexpected, as the car runs smoothly, doesn't blow smoke or cough and sputter. Was really only doing it as a last peace of mind kind of thing. :l

The question now is, is it worthwhile getting a second opinion? It just seems kind of weird that not one.. not two.. but 3 of the 6 cylinders are leaking so badly, while the others are going strong at 150-160. I'm thinking it could be a dodgy test, but the mechanic said he double checked and got the same numbers, so I'm not too sure..

I'm really quite dissapointed :l If everything checked out, it would be in my garage right now!!

Has anyone here been in a similar situation or have any advice? Not too sure where to go from here :S

Thanks guys

Lyndon

[WARLORD]

been there rebuilt mine,i drove it till i needed to do it , i was buying parts along the way,the down side is once i start buying parts i never stopped.lol

good luck with it

[R31Nismoid]

Get a 2nd opinion if you must - but either way sure does not sound good...

Walk away from the car IMO

[Duncan]

I think its more likely to be incorrect compression test results unless it is running like shit or blows heaps of smoke on boost.

was it warm when you tested it

was the battery fully charged

was the cas unplugged

was the throttle fully open while cranking

was it a screw in or push in type of tester?

[The Dan]

Surely the mechanic who compression tested it also did a leakdown test afterwards to tell you WHY the compression is down right?

If not, then get a second opinion. Sounds dodgey. I have replaced 2 comp test gauges in the last 4 years. They don't last forever

[PewPew]

Thanks for the replies guys. The car was driven to the workshop, which is about a 30 min journey at freeway speeds, so I'm guessing it was done warm?

That's the thing though.. it drives very smoothly and doesn't blow a puff of smoke even when revved up to 6k rpm. Not sure what kind of test was done though, we just left it at the mechanic's and went to grab the transfer forms and transferred the car back onto regular plates. :S Was done at a workshop I found in the WA consolidated workshop thread, and was recommended to me by forum users D:

Had a chat with the seller, he looked genuinely surprised and said he definitely wants to pay for a second opinion, so I guess I'll wait for the results of that and take it from there. :S

Also, just curious- how does the leak down test actually work? I've heard it mentioned here and there, but not 100% sure what it actually means :S

Thanks guys

[STATUS]

should always do the second test in random order too.

[Hanaldo]

Leak down test is similar to a compression test, but it measures pressure loss instead of pressure.

What they do is remove all the spark plugs, screw in a threaded coupling attached to a leakage gauge, and then feed about 80-90psi of compressed air into the cylinder. Any more than 30% leakage and you have a problem.

Leak down tests also make it alot easier to diagnose what the problem is, as Daniel pointed out. For example if you can hear the air coming out of the throttle body that would indicate a leaky intake valve. Or if a cylinder has poor compression but minimal leakage, that would usually indicate a valve-train problem, such as a collapsed lifter or worn cam lobe, etc.

[PewPew]

Oh okay thanks for the explanation Martin

Are there any workshops in Perth that you would recommend to do a second compression and leakdown test?

[blind_elk]

When you get the "second opinion" comp test, get them to do a "wet" test as well.

[PewPew]

When you get the "second opinion" comp test, get them to do a "wet" test as well.

What's a wet test?

Sounds kinky

[Brezza]

i would probably say to get a second opinion if you're really keen on the car.

if you're not, or if the second test comes back bad, WALK AWAY!!

the last thing you want is to buy a Skyline that you know is going to need work, its not cheap.

and those that say it is cheap are lying.

[Ten Four]

Hyperdrive are my favourite

Car you linked isnt cheap either.... Would want it mint and then some...

Definitely do another test and don't be scared to walk..

[PewPew]

Yeah.. if the second result is consistant with the first, I wouldn't hesitate to walk away. It's just that I'm not sure if the result is accurate. Would be a pity if I gave up on this one due to a dodgy test, as the mechanic said everything else was in top knick :l

Lol that's ironic James. The place I took it for the first test was Allstar Garage literally across the road from Hyperdrive xD

Will give them a ring tmr to see if they can book me in later this week.

Cheers

[Hanaldo]

Allstar Garage are my favs... Sean is the best in my opinion. No harm getting a second test done though, better to be safe than sorry, especially if the owner is paying for it. How long in advance did you book in at Allstar lol, they book out like 2 weeks in advance... Suppose it wasn't being tuned though.

Definitely walk away from it if the tests come back dodgy, there are plenty of R34's out there, would suck if you bought one of the lemons.

[PewPew]

Allstar Garage are my favs... Sean is the best in my opinion.

I spoke to Sean on the phone and he managed to squeeze me in the very next day

It wasn't him who did the test though..was one of the younger mechanics.

Seller said he'll get it done again today.. will let you guys know how that goes.

I really am quite keen on this car! But if the results concur with the first...

Fingers crossed!

[Ten Four]

So how'd it go mate?

[PewPew]

He was tied up with work, msged me saying he'll do it today with a kit he borrowed from work, as he's a mechanic. If that checks out, I'll get him to do another infront of me and then if a garage can verify it, I'm happy to take the car off him I'll let you guys know how it goes hopefully later tonight :S

[PewPew]

Seller insisted on a home job done by him and refused to take car to third party mechanic.. dodgy.. :S

[Trozzle]

find another car imo mate, isn't right...