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low compression--what is it?

first off then, recheck the compression. if it still yields the same numbers 
then do the leakdown test. when you have the engine at BDC for that cylinder 
some air (a little bit) will leak past. try it on a "good" cylinder to get 
and idea of how much air will leak. then hook the tester up to the "bad" 
cylinder. if its exhaust valves then you will hear it making noise from the 
tailpipe. if its intake valves then you will be able to modulate the noise 
by opening and closing the throttle plates. if its rings then you will be 
able to hear it in the oil cap hole or the crankcase breather hose. if its a 
headgasket you will hear it in the oil cap, crankcase breather hole, coolant 
bottle will bubble or the adjoining cylinder(s) spark plug hole. the first 2 
are not very likely though. and if you have uniform compression then you 
will most likely not hear it in the adjoining cylinder either.



Chris DeLong
ICQ#45030867
Seattle, WA USA
'80 16V 'Rocco ragtop
'91 GLi 2.0 16V (for sale)
'77 Rabbit 16V
'61 17 Window type II
'91 Vanagon
'84 Jetta





>From: "Michael Abatzis" <abatzis2@hotmail.com>
>To: scirocco-l@scirocco.org
>Subject: Re: low compression--what is it?
>Date: Wed, 19 Feb 2003 03:33:34 +0000
>
>yeah, i got the manual cable on the way. no, i've only comped this engine 
>with the new head this one time. tell me more about the leakdown 
>testing--should any air escape at all with the compressed air if the 
>cylinder's good? and how do i tell where it's leaking from? do i hear it 
>bubbling through the top of the head (take off the oil cap?) if it's a 
>valve problem? thanks!
>
>
>-Michael Abatzis
>Hotlanta! GA
>1988 Scirocco 2L 16v RIP-->parting, finally taking orders: 
>www.learnlink.emory.edu/~mabatzi/mikes_page1.html
>1987 Scirocco 2L 16v...
>
>
>
>
>>From: "Chris DeLong" <green536@hotmail.com>
>>Wed, 19 Feb 2003 03:25:37 +0000
>>
>>replace the auto adjust cable with a manual one.
>>I doubt its a headgasket. although I wouldnt rule it out. coolant/oil 
>>transfer does not always happen wiht a blown hg. have you comped it more 
>>than once? if not I would suggest you do that first. you can also use your 
>>compression tester lead for a leakdown tester. roll the engine to BDC and 
>>take the Shrader (sp?) valve out of the end. then connect it to you air 
>>line from your air compressor. then listen to where the air is escaping 
>>from. this will give you a good idea about what is wrong.
>>
>>
>>
>>Chris DeLong
>>ICQ#45030867
>>Seattle, WA USA
>>'80 16V 'Rocco ragtop
>>'91 GLi 2.0 16V (for sale)
>>'77 Rabbit 16V
>>'61 17 Window type II
>>'91 Vanagon
>>'84 Jetta
>>
>>
>>
>>
>>
>>>From: "Michael Abatzis" <abatzis2@hotmail.com>
>>>To: scirocco-l@scirocco.org
>>>Subject: Re: low compression--what is it?
>>>Date: Wed, 19 Feb 2003 03:14:50 +0000
>>>
>>>heh heh. yeah, i bought some valve cleaner (one for oil, one for gas), 
>>>and gave it a typical flogging. holding off till the weekend for a good 
>>>one. auto-adjust clutch cable started to go yesterday (it never ends). 
>>>don't want to go to far before i replace it this weekend. i'm hoping it's 
>>>stuck/dirty valves (this happened once on the old 1.8). but could it be 
>>>the head gasket? or would i definitely get oil in the coolant/coolant 
>>>loss? i'm going to recheck the head stud torques this weekend, just in 
>>>case.
>>>
>>>
>>>-Michael Abatzis
>>>Hotlanta! GA
>>>1988 Scirocco 2L 16v RIP-->parting, finally taking orders: 
>>>www.learnlink.emory.edu/~mabatzi/mikes_page1.html
>>>1987 Scirocco 2L 16v...
>>>
>>>
>>>
>>>
>>>>From: "Chris DeLong" <green536@hotmail.com>
>>>>To: abatzis2@hotmail.com, scirocco-l@scirocco.org
>>>>Subject: Re: low compression--what is it?
>>>>Date: Wed, 19 Feb 2003 02:50:58 +0000
>>>>
>>>>put the plugs back in, go flog the hell out of it, bring it back in and 
>>>>do another comp test. it is possible for carbon deposits to get stuck 
>>>>between the valve and the seat. flogging it will hopefully get rid of 
>>>>any pesky carbon deposits and yeild a better comp test. oil on the 
>>>>threads usually is from undertightening the plugs.. HTH
>>>>
>>>>
>>>>
>>>>Chris DeLong
>>>>ICQ#45030867
>>>>Seattle, WA USA
>>>>'80 16V 'Rocco ragtop
>>>>'91 GLi 2.0 16V (for sale)
>>>>'77 Rabbit 16V
>>>>'61 17 Window type II
>>>>'91 Vanagon
>>>>'84 Jetta
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>From: "Michael Abatzis" <abatzis2@hotmail.com>
>>>>>To: scirocco-l@scirocco.org
>>>>>Subject: low compression--what is it?
>>>>>Date: Tue, 18 Feb 2003 23:02:32 +0000
>>>>>
>>>>>i've had an oil leak of unknown source for 3months, and have recently 
>>>>>been noticing poor power. finally cleaned the engine last week, and 
>>>>>despite losing 1/2 qt of oil, the outside is still clean. i did a 
>>>>>compression test today, with the following results:
>>>>>
>>>>>215/220/230/100
>>>>>
>>>>>yeah, the gauge has always read high (210-220 has been average across 3 
>>>>>engines), but obviously #4 is the concern. plug threads were oily, but 
>>>>>plugs themselves weren't fouled. pistons from what i saw were gunky.  
>>>>>wet compression raised #4 to 170, but 1/2/3 also increased by 40-50 
>>>>>psi, so i don't know what to make of that. coolant has no oil in it.
>>>>>
>>>>>so, what's up? head was replaced (with hg) maybe 6 mos ago, and had 
>>>>>been recently redone apparently (brett c?). i'm thinking headgasket v. 
>>>>>stuck/dirty valves v. leaky valve guides v. (less likely) rings/other 
>>>>>bad stuff. any ideas, or how to better eval? btw, my car is way worse 
>>>>>than yours cathy.
>>>>>tia,
>>>>>
>>>>>
>>>>>-Michael Abatzis
>>>>>Hotlanta! GA
>>>>>1988 Scirocco 2L 16v RIP-->parting, finally taking orders: 
>>>>>www.learnlink.emory.edu/~mabatzi/mikes_page1.html
>>>>>1987 Scirocco 2L 16v...
>>>>>
>>>>>
>>>>>
>>>>>
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