| Author |
Message |
Dave Penhale (Dapper)
Member
Username: Dapper
Post Number: 305
Registered: 4-2002
| | Posted on Monday, October 21, 2002 - 3:50 am: | |
Just for my info any chance someone on here could give a reasonably detailed explanation of the 'leakdown' test procedure, particularly wrt to F cars if this means there are any specific idiosyncracies to be taken into account.
Thanks |
Mark Eberhardt (Me_k)
Junior Member
Username: Me_k
Post Number: 136
Registered: 5-2002
| | Posted on Saturday, October 19, 2002 - 10:16 am: | |
When I did my car cold the numbers were all over the place with #1 around 20%. This caused my heart stop because the reason I was doing the test is the car loss #1 during dyno tuning at about 6600 rmp. The plug had clearly been hit causing it close gap. It compression tested perfect (hot) on the dyno, but didn't run when the plug was changed. It was cold by the time I got the leak-down tester. It turned out the fuel injector had failed spitting part of it's valve into the cylinder, hitting the plug, then exited the exhaust. I re-did it hot and all were less than 1%. I don't think that if you actually did harm when the belt slipped it would be only 1 cylinder so I'm voting with the it's probably fine group.
p.s. stay way from lucus electronic fuel injectors, I had a total of 3 fail exactly the same way before changing brands. |
Paul Newman (Newman)
Member
Username: Newman
Post Number: 602
Registered: 12-2001
| | Posted on Friday, October 18, 2002 - 5:02 pm: | |
Perform the test, leakdown or compression test on a warm engine. Verify correct belt timing and run the car, then retest. Also, if doing a compression test, hold the throttle wide open during the test. |
David Jones (Dave)
Member
Username: Dave
Post Number: 371
Registered: 4-2001
| | Posted on Friday, October 18, 2002 - 4:36 pm: | |
You are correct Philip, a leakdown will not disclose valve guide wear... |
Philip Airey (Pma1010)
New member
Username: Pma1010
Post Number: 28
Registered: 7-2002
| | Posted on Friday, October 18, 2002 - 4:19 pm: | |
I don't want to be a contrarian here, and maybe I am missing something, but I thought (i) leakdown told you about bores and rings, not guides; and (ii), 20 is high. When I had a leakdown done as part of the PPI, one cylinder was 12 (as I recall), the rest were in the 5 to 7 range. 14 seemed to be a magic number for the service tech.
If it were me, I'd wait until I was going to look at the top end (belts, valve shims...) and plan on pulling the head and checking rings, bores et al at the time.
Just my 2 cents |
Paul Sloan (Sloan83qv)
Member
Username: Sloan83qv
Post Number: 385
Registered: 3-2001
| | Posted on Friday, October 18, 2002 - 7:08 am: | |
The cams out does not make a difference as you could have carbon buildup on a valve seat keeping the valve from closing completely let alone you could have a slightly bent valve stem again keeping the valve from closing. |
Bill V. (Doc)
Junior Member
Username: Doc
Post Number: 157
Registered: 9-2001
| | Posted on Friday, October 18, 2002 - 6:53 am: | |
I recently purchased an '85 QV and the leakdown #'s on it were almost identical to those you reported, with one cylinder reading 20%. I sought the opinions of 4 reputable Ferrari mechanics and put it out out Chat ( in 6/02). No one thought that the 20% was that outlandish for a stone cold motor ( to my surprise). Obviously, the readings will be better on a hot engine and/or with wet readings. In my case, I bought the car and it has performed perfectly. |
Timothy Fulmer (Tf308)
New member
Username: Tf308
Post Number: 10
Registered: 5-2002
| | Posted on Friday, October 18, 2002 - 6:15 am: | |
P.S. the cams are out so the idea of an open valve need to be removed from the equation. |
Timothy Fulmer (Tf308)
New member
Username: Tf308
Post Number: 9
Registered: 5-2002
| | Posted on Friday, October 18, 2002 - 6:14 am: | |
The reason I tested was that in trying to break loose the intake cam pulley while I am doing a belt job the belt slipped and threw off the timing. (All has been done by hand ie the car was never started out of timing, the car ran fine before) I wanted to make sure I didn't hit a valve so I did the cold leakdown to see if there was any leakage.
the odd thing was that pressurizing #2 shot the paper towel out of the #4 spark pug hole. Once I get the cams back in and get the car running I will test hot...any other comments or ideas greatly appreciated....and yes ignorance is bliss. |
Lawrence Coppari (Lawrence)
Member
Username: Lawrence
Post Number: 318
Registered: 4-2002
| | Posted on Friday, October 18, 2002 - 5:51 am: | |
I'm not going to test mine. Ignorance is bliss.
--The Ostrich |
BretM (Bretm)
Advanced Member
Username: Bretm
Post Number: 2763
Registered: 2-2001
| | Posted on Thursday, October 17, 2002 - 10:45 pm: | |
Remember that doing a lot more testing to make sure it's leaking it is a lot easier than correcting a cylinder with 20% leakdown. I kind of doubt it's leaking unless you have a reason to think it is for some reason, of course though this in no way rules out the possibility. How come you tested anyways? Do the front bank also, only takes a couple minutes and would be interesting to see. |
Rob Lay (Rob328gts)
Board Administrator
Username: Rob328gts
Post Number: 2418
Registered: 12-2000
| | Posted on Thursday, October 17, 2002 - 10:31 pm: | |
Did you run it hard before the test? If not, you should, and try again. |
Paul (Pcelenta)
Junior Member
Username: Pcelenta
Post Number: 184
Registered: 7-2002
| | Posted on Thursday, October 17, 2002 - 9:03 pm: | |
Could you hear air exiting the exhaust or in the case? I'm wondering if maybe the valves weren't fully closed...I'd retest that cylinder again if you haven't done so already |
Timothy Fulmer (Tf308)
New member
Username: Tf308
Post Number: 8
Registered: 5-2002
| | Posted on Thursday, October 17, 2002 - 8:07 pm: | |
OK...did a leak down on my 84 QV. It has 23K miles and I have only had a chance to do the rear bank. I did this COLD. #1 6% #2 7% #3 6% and #4 was 20%. The last number really shocked me. What are your opinions? |