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Old 07-27-2007, 11:50 PM
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Default Need Valve job- 100k 4.2l a6, love it or leave it?

Was told today that I need to replace valves to remedy oil burning problem-Quoted $3k by audi master mechanic working through small local shop (he is moonlighting from local audi dealer). I also need a new catalytic converter (1k?) and maybe oxygen sensors. The car has 100k miles, is in otherwise excellent condition (just replaced timing belt, water pump etc.). I'm looking for advice for how to proceed. Audi mechanic recommended doing a trade-in with the dealer, but I'm leary. Assuming that no other engine damage, should I invest the 4k? I love the car, but am only married to my wife.... Thanks.
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Old 07-28-2007, 07:53 AM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

First of all I'd get a second opinion. Do you have the results from a compression/leak down test?

Next, evaluate the rest of the car to get a feel for what's next. If your pretty comfortable that you will have a reliable car, I'd get the work done.

I have never been able to 'get over' on a dealer when trading a car in. It is likely that the trade-in will net you more than $3k less than if you sold the car outright.
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Old 07-28-2007, 08:01 AM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

Wow, tough news. That seems to be one of the bigger-hit service items that comes up with long term 4.2L. What year is the car? I read from one source that it mainly affected '00-01 and that there was a design modification to reduce the wear in later models.

I do believe servicing the heads/valve seals requires pulling the motor- a dicey proposition for one guy in a small shop unless he's been through the drill enough times to be really familiar with all the electrical connections & etc. The advice to have a leakdown test is sound, it will help quantify not only whether the proble is valves/seals, but also how bad it is. You could go some time just dealign with some excess oil burning-- but it sounds like it already toasted your cat so it probably isn't minor if thats the source.

At any rate, for 3K you might be able to get a warranteed used motor with fewer miles. A bit of a dice-roll, but means less wear on some other components (rod and main bearings, rings) if it was properly maintained.

Most folks seem to feel OK about hosing a dealer..but of courseany dealer offering a decent trade valuewill either sell the car or auction it to a used dealer that will sell, so trading defective vehicles probably does mean screwing some 'average joe' somewhere.

I'd say think about how long you'd likely keep the car following a repair and work out what the cost of that 'time' is, compared with a payment on something a bit younger if you trade. It all comes downto your gut though.
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Old 07-28-2007, 08:39 AM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

Also, there is a TSB on the ECU WRT the cats. It may be the catylitic converter is OK.
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Old 07-28-2007, 07:53 PM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

Thanks for getting back to me so quickly. They did the compression test- and ascertained the valve problem. What type of results should I ask for, would be meaningful to get? This is a second opinion, as the dealer already said I needed a new engine about a year ago, and quoted about 10k. Because i had never worked with this one, and have had generally negative experiences, tried to find independent who had Audi background. The mechanic I am now dealing with was apparently certified by Audi.
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Old 07-28-2007, 08:11 PM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

Thanks for the sympathetic and complete feedback. It is indeed a '00. Is the leak down test different from a compression test? I was told that they would indeed need to disassemble the motor to get at the valves. I'm not as much concerned about the skill set involved, as from what I can tell, the same guy has (and continues to work) at the dealer for upwards of a decade.

They seem to be straight shooters as did inform me of the trade in dynamics - yes, even though it is defective, would probably just auction. I don't like the thought of anyone else getting stuck. I bought the car unseen on Ebay (first and only purchse)- and am taking my lumps.

My gut tells me that the car is solid, and as long as the engine isn't otherwise damaged, that it could hold up well for a few more years. My main concern in investing another 4-5k total is how to remove uncertainty that engine will be solid. I was told that the worn valves were due to not changing oil over a long period- and that pistons could also be worn etc. What typically causes the valves to wear? After replacing, wouldn't the engine be - in a sense- refurbished? What other parts might I consider replacing while the car engine is disassembled? Other major wear/tear areas to check? Thanks for sharing your insights!
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Old 07-28-2007, 08:19 PM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

Not sure I got all of the acronyms, but the cat is definitely shot, with pieces of it rattling around. I'm not sure I understood, but apparently there are two CATs, and only one is shot. Mechanic said that he could try to get a non-audi cat and weld it in place to save costs (new audi CAT runs $900?)- mechanic has an older Audi himself, and did this successfully. Because there was some kind of curvature in mine, didn't know if this would work. Thank you.
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Old 07-28-2007, 08:39 PM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

Leak down test: http://www.type2.com/library/engineg/leaktst.htm

How much oil are you using?

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Old 07-28-2007, 08:52 PM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

I am using a quart every 250-300 miles. Thanks for leakdown info.- don't think this was completed. Using 20w 50 oil based on recommendation from previous mechanic. Owner who I bought from was using synthetic. Could part of the problem be from switching oils? Most of what I see recommended on this site is synthetic- but I'm sure this varies based on engine/age and condition engine etc.
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Old 07-28-2007, 09:11 PM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

For your information (FYI): ECU = Electronic Control Unit (computer), TSB = Technical Service Bulletin (from Audi and typically they will fix at no charge), and WRT = with regard to. Sorry for the shorthand.

Your consumpton is pretty severe, I doubt there is a lubricant or additive fix.

It sounds like you have an honest shop, perhaps they can help you with understanding what may be on the horizon if you go ahead with the repair.

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Old 07-28-2007, 09:47 PM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

BTW, The only one I got was the WRT- business speak
While honesty is all relative, I believe these guys are straight shooters. I found them more or less by accident (the father of the shop owner has an auto parts store- and sold me on the fact they have one of best audi mechanics moonlighting with them)- and have never transacted with them.

I'm looking now for them to give me an estimate of this entire repair, and to do a comprehensive check as to what other work could be done. I would need to compare to what's on offer there to possible trade in. Since I'm not in position to buy new, I'd be dealing with somebody else's used car unknown's- although if it was from the dealer might there also be some kind of warrantee? I appreciate all of the advice.

One more question- with the known "wear" issues on the 2000 A6 4.2L, and assuming I do the repair- any estimates on how many more miles I can reasonaly expect?
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Old 07-28-2007, 10:05 PM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

I would have them check the front suspension for wear and service the transmission.

This is a big long shot, but under the heading of little to lose, I might try a couple of AutoRx treatments http://www.auto-rx.com/
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Old 07-28-2007, 10:11 PM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

It sounds like low risk to try, certainly compared with the alternatives! Thanks again for all the quick replies and good insights.
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Old 07-28-2007, 11:32 PM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

Oil consumption wouldn't lead me to believe the valves are the actual problem. How is the valve itself going to wear? It's a solid piece. (I had over 200k on original valves in my last Audi until the timing belt broke and they hit pistons, had to replace them). The valve stem seals are rubber and they do wear out allowing oil to get down past the valve into the cylinder, and then "burn" (mix with the air/fuel mixture and ignite with the spark, then get blown out the exhaust valve and through the exhaust). Also lets say the valve stem seals are fine, it could also be blow-by from worn piston rings, that's why I'd do a compression check and see what all 8 cylinders read compare it to spec. They should all be within 10-15% of each other.

If they have to change the stem seals it could probably be done without pulling the engine out of the car, I don't see why they'd need to even if they pull the heads. If they heads are going to be removed, obviously the head gaskets will be changed, and probably all the gaskets and seals from the heads up. Still $4000 is VERY steep. Where is this guy getting the parts? What makes him think the valves themselves are bad and it's not just the stem seals or piston rings? If it's rings, well then the engine needs to come out, and the bottom end needs to be disassembled. In that case I'd say do new rings, and new main and rod bearings.
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Old 07-29-2007, 10:40 AM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

Thanks for yet another informative post! When he mentioned valves, he was likely referring to the valve stem seals. Is the relative value on compression test (i.e., 10-15% of each other) vs. a nominal value compared to the spec what I should be looking for? Do you know these ratings/ranges (this is not the 11:1 ratio mentioned in car specs)?? I understood that they would be pulling off the "upper half" of the engine, not the entire engine. No discussion of heads/head gaskets, but will ask. The 4k is including possible 1k for a CAT. Assuming was going to put in Audi parts. What would you consider reasonable if he was just changing the valve seals in terms of cost (parts/labor)?

Would a compression test determine whether valve seals or bad, or could it still be stem seals or piston rings? It sounds like leakdown would yield more specific info.? Given that compression test determined a problem, does it make sense to have mechanic open up engine- or should I ask for leak down?

re. compression test
"It can only be used to check engine condition by comparing cylinders to each other or a past norm. Variables such as cam profile, engine cranking speed etc, will affect the readings."
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Old 07-30-2007, 08:46 AM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

A compression check will tell you if a given cylinder is able to compress (nut not necessarily to maintain) the intake charge (air plus fuel) to a reasonable pressure. 150 psi would be about normal for your car. Any component that helps acheive the compression, including pistons, rings, head gasket and valves, will be tested as a set in a compression test. Evaulation of the results, combined with a few old tricks, can help determine the root cause of the problem. One old trick is to listen for the compressed air leaking into the intake or exhaust manifolds. This can be done with a mechanic's stethiscope. Hearing the air escape into either of these manifolds means that the valves are leaking. The valves leak, in this sense, at the interface between the valve head and the valve seat. It is these two surfaces that are re-ground during a valve job, providing a matching set of angles and surfaces to provide proper sealing. However, failure in this area will NOT lead to excessive oil consumption.

The valve seals and guides will, if worn, allow oil to leak past the seal, down the stem of the valve and into the intake port of the head. these would have to be VERY, VERY worn to allow 1 quart per 250 miles of driving of oil consumption.

Your next culprit is the head gasket. A leaking head gasket would allow oil to leak into a cylinder and be burned. this would show up as a single low compression reading.

Bad rings would show up as multiple low compression readings. This would also allow oil into the cylinder where it would be burned.

If I were you, I would plan on a complete engine rebuild, including rings, bearings, new oil pump and seals to go with your head job. Since the majority of the labor expense is the removal and replacement of the engine from the car, you might as well pay for that only once.

Good luck and sorry to hear about your bad eBay experience.

Bob
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Old 07-30-2007, 10:05 AM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

Oh, forgot to mention, a leak down test will test the ability of a cylinder to hold the pressure that the comrpession stroke creates. This will tell how well the components involved are doing their sealing jobs and can also, through the above mentioned stethescope method, help determine the root cause of a failure.

Bob
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Old 07-30-2007, 10:08 PM
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Default RE: Need Valve job- 100k 4.2l a6, love it or leave it?

Hello Bob- I was at the mechanic today and they did indeed do compression and leak down tests, and believe that it is the valve seals. The quote is now at 4k, just to change the valve seals (with 1.5 k additional for the Cat). I asked about other engine parts that should be changed, and they did not mention oil pump, bearings. rings, head gasketetc. I am going to do this once, so will consider complete rebuild. How much additional would all of this add? (they did mention that almost all of cost quoted for engine was labor). I am going to get the exact quote

I am curious about the valveseat/head regrinding- I understood that they will just be replacing the seals. Also no mention of the the valve guides. I will ask about what they have in mind. Thanks for the advice.

Edward

FYI- As a first step, I am going to do a complete engine flush. Audi has been having a lot of trouble with the A4 turbo engines because the american oil is not as clean as the european- therefore, since the A4engines get so hot, there have been problems with sludge buildup. About 6 months ago, audi started providing dealers with a wash kit that is apparently very effective at removing engine sludge. I'll keep you all posted. Will cost $160.
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