A question for people who know about cylinder compression...

Zdrajca Polski · 04-22-2005, 11:20 AM

I had my compression checked today and it reads as follows: Passenger side cylinders read 150,150,170 and the driver side ones are 100,70,90. My mechanic told me that'd bad. More than likely the 70 and 90 are bad piston rings, and the 100 is going bad. I know the valve stem seals gotta go but is it worth it just selling the car and getting another one. This is coming from a college student who doesn't have $$$. Opinions?

CrazyCab · 04-22-2005, 11:30 AM

Junkyard for a couple hundred bucks and swap it in.

If your running a 12 valve 2.8 liter V6, they are relatively easy to find and somewhat inexpensive.

Better than rebuilding the motor you have, plus if your gonna sell it with a bad motor be prepared to take a big hit in selling price.

KeithS4 · 04-22-2005, 11:38 AM

depends the condition of the rest of the car. (and how much you care about it) Presumably you need a car, so it then is a question of if the rest of the car is worth putting the $ into a motor, or will you be spending more to get another car. Also mileage is a consideration. putting $ into a car with high mileage can be a losing proposition - there may be other things that break later.

quattrorally · 04-22-2005, 12:00 PM

Could also be a lot of carbon build up. you should do a search on seafom.

When I was buying my 90csq my compression sucked (not quite as bad) and after the treatment it went to factory specs !

hope this helps.

CrazyCab · 04-22-2005, 12:08 PM

Plus that one cylinder is running at 70 or so, do you think Carbon build up could do that?

Zdrajca Polski · 04-22-2005, 12:27 PM

could the seafoam damage the rings if they're already bad, supposedly. I don't want to make my **** hole any bigger.

moribundman · 04-22-2005, 01:03 PM

I suppose that's possible. :-(

How many miles are on the engine?

A few PSI difference could be attributed to one or a few sticky rings due to carbon buildup, but I'm afraid your numbers go beyond that scenario.

Zdrajca Polski · 04-22-2005, 03:00 PM

Any estimate on the life of the engine?

moribundman · 04-22-2005, 03:11 PM

I guess, cleaning could actually decrease compression and increase blowby, making things worse.

How's the engine run? How much oil does it burn? How many miles are on the motor?

Minimum compression is ~109 psi. Cylinders may not deviate more than 43 psi from each other.

A leakdown test can pinpoint if rings, cylinders, or if valve stem seals are bad.

Zdrajca Polski · 04-22-2005, 04:07 PM

That's the weirdest thing to me. Burns bout half a quart per week with 151k on the clock. What's a leakdown test. Is it mechanic only. Got a file on how it's done?

04-22-2005, 11:30 AM	#2
CrazyCab AudiWorld Super User Garage is empty, add now Join Date: Jun 2004 Posts: 4,359	Well depending on what motor you have you could always find a used one in a Junkyard for a couple hundred bucks and swap it in. If your running a 12 valve 2.8 liter V6, they are relatively easy to find and somewhat inexpensive. Better than rebuilding the motor you have, plus if your gonna sell it with a bad motor be prepared to take a big hit in selling price.

04-22-2005, 11:38 AM	#3
KeithS4 New Member Garage is empty, add now Join Date: Mar 2000 Posts: 106	Depends on the rest of the car depends the condition of the rest of the car. (and how much you care about it) Presumably you need a car, so it then is a question of if the rest of the car is worth putting the $ into a motor, or will you be spending more to get another car. Also mileage is a consideration. putting $ into a car with high mileage can be a losing proposition - there may be other things that break later.

04-22-2005, 12:00 PM	#4
quattrorally AudiWorld Senior Member Garage is empty, add now Join Date: Jan 2005 Posts: 1,123	Re: A question for people who know about cylinder compression... Could also be a lot of carbon build up. you should do a search on seafom. When I was buying my 90csq my compression sucked (not quite as bad) and after the treatment it went to factory specs ! hope this helps. __________________ Some are here and some are gone: B6 A4 1.8Tq B5 S4 B5 A4 1.8Tq B4 90 12v CSq Old BMW 318i Old Honda civic Very old VW Rabit Very old Mazda 626

04-22-2005, 12:08 PM	#5
CrazyCab AudiWorld Super User Garage is empty, add now Join Date: Jun 2004 Posts: 4,359	Yeah but that would be a hell of a lot of carbon build up Plus that one cylinder is running at 70 or so, do you think Carbon build up could do that?

04-22-2005, 12:27 PM	#6
Zdrajca Polski AudiWorld Senior Member Garage is empty, add now Join Date: Dec 2004 Posts: 617	I got a bottle of seafoam but... could the seafoam damage the rings if they're already bad, supposedly. I don't want to make my **** hole any bigger.

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04-22-2005, 01:03 PM	#7
moribundman AudiWorld Super User Garage is empty, add now Join Date: Jan 2003 Posts: 9,296	You think the carbon deposists are holding the remnants of the worn rings in their grooves? I suppose that's possible. :-( How many miles are on the engine? A few PSI difference could be attributed to one or a few sticky rings due to carbon buildup, but I'm afraid your numbers go beyond that scenario. __________________ Mhmm, donuts...

04-22-2005, 03:00 PM	#8
Zdrajca Polski AudiWorld Senior Member Garage is empty, add now Join Date: Dec 2004 Posts: 617	That too i guess. Can it possibly cause damage? That's my main question... Any estimate on the life of the engine?

04-22-2005, 03:11 PM	#9
moribundman AudiWorld Super User Garage is empty, add now Join Date: Jan 2003 Posts: 9,296	More damage? *EDITED to correct units!* I guess, cleaning could actually decrease compression and increase blowby, making things worse. How's the engine run? How much oil does it burn? How many miles are on the motor? Minimum compression is ~109 psi. Cylinders may not deviate more than 43 psi from each other. A leakdown test can pinpoint if rings, cylinders, or if valve stem seals are bad. __________________ Mhmm, donuts...

04-22-2005, 04:07 PM	#10
Zdrajca Polski AudiWorld Senior Member Garage is empty, add now Join Date: Dec 2004 Posts: 617	The engine runs and sounds great... That's the weirdest thing to me. Burns bout half a quart per week with 151k on the clock. What's a leakdown test. Is it mechanic only. Got a file on how it's done?

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04-22-2005, 04:07 PM
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