Broken piston rings? ('99 Golf GTi)
Discussion
Chaps,
Just had a call from an old friend. Not someone who knows anything much about cars ...
They have a '99 Golf GTi. Bought from his brother. Full service history. I don't know what the mileage is or what engine it is.
It developed a mis-fire, and they took it (via a circuitous route) into the local VW dealer. Who had a look, found oil on the spark plugs and have said it is 'probably broken piston rings'. I don't know what other tests have been run (I can call the dealer on Monday I suspect), but they have quoted £250 to take the head off and have a look, another £250 to put the head back on and £2500 for a new engine ...
Questions ....
1) Can you diagnose broken piston rings from taking the head off? I wouldn't have thought you could see enough down the side of the pistons, unless you are looking for tell-tale signs on the bores or possibly looking at the valve stem guides and seals to make sure that they aren't the problem.
2) Broken piston rings? Really? I have never heard of a VW engine suffering from this, unless you are doing silly things with it (which these people won't have been.)
Suggestions?
My thoughts are that a dealer is the most expensive way of doing anything, so take it elsewhere. And putting a new engine in a car like that is daft - much better to find a good breaker, and maybe the breakers yard can do the work as well.
All help appreciated. Thanks.
Oli.
Just had a call from an old friend. Not someone who knows anything much about cars ...
They have a '99 Golf GTi. Bought from his brother. Full service history. I don't know what the mileage is or what engine it is.
It developed a mis-fire, and they took it (via a circuitous route) into the local VW dealer. Who had a look, found oil on the spark plugs and have said it is 'probably broken piston rings'. I don't know what other tests have been run (I can call the dealer on Monday I suspect), but they have quoted £250 to take the head off and have a look, another £250 to put the head back on and £2500 for a new engine ...
Questions ....
1) Can you diagnose broken piston rings from taking the head off? I wouldn't have thought you could see enough down the side of the pistons, unless you are looking for tell-tale signs on the bores or possibly looking at the valve stem guides and seals to make sure that they aren't the problem.
2) Broken piston rings? Really? I have never heard of a VW engine suffering from this, unless you are doing silly things with it (which these people won't have been.)
Suggestions?
My thoughts are that a dealer is the most expensive way of doing anything, so take it elsewhere. And putting a new engine in a car like that is daft - much better to find a good breaker, and maybe the breakers yard can do the work as well.
All help appreciated. Thanks.
Oli.
Broken rings happen, as do holed pistons, but usually only on one cylinder, you say all the plugs are oiled??? More likely stem seals if its all of them
Is it turbo charged, is the turbo just pooring oil into the engine. Take the boost pipe off the turbo and feel the free play (up and down + back and forth)in the shaft, should be virtually none.
You could ring round engine builders and see if anyone has a bore scope, they could then look at the bores by just taking the plugs out.
(1) Yes broken ring will indeed leave big tell tail marks on the bore. While the head is off they can check and rule out valve guide/ stem seal issues.
(2) Can happen to ANY engine, I only see in on a 1.8T A4 that the customer overheated.
If it need a new engine, and it may well do. Its probably not an economical repair at main dealer rates.
Is it turbo charged, is the turbo just pooring oil into the engine. Take the boost pipe off the turbo and feel the free play (up and down + back and forth)in the shaft, should be virtually none.
You could ring round engine builders and see if anyone has a bore scope, they could then look at the bores by just taking the plugs out.
(1) Yes broken ring will indeed leave big tell tail marks on the bore. While the head is off they can check and rule out valve guide/ stem seal issues.
(2) Can happen to ANY engine, I only see in on a 1.8T A4 that the customer overheated.
If it need a new engine, and it may well do. Its probably not an economical repair at main dealer rates.
Tame tech,
Thanks for your answer. It's appreciated.
The engine isn't turbocharged - it's the 2.0 n/a, which makes things simpler. Mileage is 66,000, and it has a full service history from day 1.
I have just spoken with the technician who did the work thus far. He has done a compression test which came back normal. The only symptoms are oil on plug 3, which causes a misfire. He cleaned up plug 3 and all was well again. (Although the assumption is that it will re-occur).
The technician recommends taking the head off for a better look. (Quote - £235 for removal of head, £552 for removal and refitting). His best guess is either valve guide (although I would have thought it would be the stem oil seal), or broken piston ring. He can't say more than that at this stage.
The idea of a bore scope is a good one, thanks. That could well be a go-er. Have a look at the bores on the basis that if the piston ring is broken then the bores will be badly scraped. Easy diagnosis.
However, my thoughts are that the valve guide is more likely. My experience with VW engines (admittedly Mk1 - Mk3 rather than Mk4) is that the valve guides do wear fairly often, but I have never seen a broken piston ring. Having said that, valve guide wear at such a low mileage is unlikely.
Yes, it is main dealer. And no, a new engine would certainly not be economical at those rates (c£2,800). Although a swap for a unit from a breaker would be much cheaper.
Thanks again for your input.
Oli.
Thanks for your answer. It's appreciated.
The engine isn't turbocharged - it's the 2.0 n/a, which makes things simpler. Mileage is 66,000, and it has a full service history from day 1.
I have just spoken with the technician who did the work thus far. He has done a compression test which came back normal. The only symptoms are oil on plug 3, which causes a misfire. He cleaned up plug 3 and all was well again. (Although the assumption is that it will re-occur).
The technician recommends taking the head off for a better look. (Quote - £235 for removal of head, £552 for removal and refitting). His best guess is either valve guide (although I would have thought it would be the stem oil seal), or broken piston ring. He can't say more than that at this stage.
The idea of a bore scope is a good one, thanks. That could well be a go-er. Have a look at the bores on the basis that if the piston ring is broken then the bores will be badly scraped. Easy diagnosis.
However, my thoughts are that the valve guide is more likely. My experience with VW engines (admittedly Mk1 - Mk3 rather than Mk4) is that the valve guides do wear fairly often, but I have never seen a broken piston ring. Having said that, valve guide wear at such a low mileage is unlikely.
Yes, it is main dealer. And no, a new engine would certainly not be economical at those rates (c£2,800). Although a swap for a unit from a breaker would be much cheaper.
Thanks again for your input.
Oli.
Presumably you've tried just replacing the plugs with new? A misfire can result in a dirty (sooty) plug, unless its dripping with oil then a ring or seal failure sounds unlikely at the mileage you state.
Also strange that compression is good if there is a ring fault, you would expect to see some imbalance. A leakdown test is usually better than compression FWIW.
Failed stem seal is possible, if this has happened you would typically expect a puff of blue smoke out of the exhaust on startup (oil drips down and pools in the inlet) after the car has been standing overnight, but no smoke when running. Failed ring would typically smoke all the time.
AdrianR
Also strange that compression is good if there is a ring fault, you would expect to see some imbalance. A leakdown test is usually better than compression FWIW.
Failed stem seal is possible, if this has happened you would typically expect a puff of blue smoke out of the exhaust on startup (oil drips down and pools in the inlet) after the car has been standing overnight, but no smoke when running. Failed ring would typically smoke all the time.
AdrianR
Adrian,
Thanks.
I've now looked at the car. Compression on 1 and 3 (3 being the supposed problematical one, 1 being taken as a control) were both excellent. A spark gap tester applied to 1 and 3 also produced excellent sparks. No visible smoke on running, although I haven't seen it starting after sitting overnight.
Car didn't have any fault codes, and a live read-out from lambda looked good. BUT it doesn't run as it should - it occasionally misses on idle and stumbles slightly when you drive it. All is not right.
New plugs are now procured and we'll be fitting them (hopefully) tomorrow. We'll see what results that brings.
I have heard of problems on the 2.0 8v VW engines used extensively in town, whereby the piston rings (and indeed whole combustion chamber) gets carbon-ed up and can cause misfires and excessive oil usage. Solution is to clean the combustion chamber (with suitable products), change the oil and give the engine a really good Italian tune-up. If the new plugs don't solve the problem then we'll be going down this route.
I'll keep this thread updated.
Oli.
Thanks.
I've now looked at the car. Compression on 1 and 3 (3 being the supposed problematical one, 1 being taken as a control) were both excellent. A spark gap tester applied to 1 and 3 also produced excellent sparks. No visible smoke on running, although I haven't seen it starting after sitting overnight.
Car didn't have any fault codes, and a live read-out from lambda looked good. BUT it doesn't run as it should - it occasionally misses on idle and stumbles slightly when you drive it. All is not right.
New plugs are now procured and we'll be fitting them (hopefully) tomorrow. We'll see what results that brings.
I have heard of problems on the 2.0 8v VW engines used extensively in town, whereby the piston rings (and indeed whole combustion chamber) gets carbon-ed up and can cause misfires and excessive oil usage. Solution is to clean the combustion chamber (with suitable products), change the oil and give the engine a really good Italian tune-up. If the new plugs don't solve the problem then we'll be going down this route.
I'll keep this thread updated.
Oli.
It's probably just a leaking cam cover gasket leaking oil into the spark plug/coil pack bores (if it's a 20v engine). Once it gets wet in there it can cause a bad misfire, and if they have taken the plugs out and got them wet with oil on the way out then they will have probably presumed the oil is inside the cylinder.... I've worked in both VW & Audi dealerships and there's plenty of idiot mechanics working there who will jump to conclusions before diagnosing the fault correctly. And no, I'm not saying all dealership techs are idiots... just some of them.
Edited by Mikey-S on Monday 13th July 20:14
Mikey.
Thanks. Your post has reminded me to update this thread.
We (another friend and I) drove it. It was clearly misfiring on a cylinder. We changed the plugs (8v 2.0 Mk4 engine. What a pig to work on! Needed to remove half the intake tract to get to the plugs ... ) Also cleaned out the spaces around the plugs and the ends of the plug leads. After that, all was fine - no misfire.
Took it for a hard run of 10 miles or so, hoping to burn out any residual carbon in the cylinders (owners don't drive it long or hard - just gentle potting from traffic light to traffic light.) Then gave it back to the owners, and will wait and see what the outcome is. I don't feel that we have fixed it, and am suspecting that the problem will return, but we will see.
Idiot mechanics in the dealership? A possibility. Time will tell.
Oli.
Thanks. Your post has reminded me to update this thread.
We (another friend and I) drove it. It was clearly misfiring on a cylinder. We changed the plugs (8v 2.0 Mk4 engine. What a pig to work on! Needed to remove half the intake tract to get to the plugs ... ) Also cleaned out the spaces around the plugs and the ends of the plug leads. After that, all was fine - no misfire.
Took it for a hard run of 10 miles or so, hoping to burn out any residual carbon in the cylinders (owners don't drive it long or hard - just gentle potting from traffic light to traffic light.) Then gave it back to the owners, and will wait and see what the outcome is. I don't feel that we have fixed it, and am suspecting that the problem will return, but we will see.
Idiot mechanics in the dealership? A possibility. Time will tell.
Oli.
have to bump this topic up.
I have a Astra MK4. It has a strange probelm of burning oil. When the car just warmed up, the engine runs "no problem"---no blue smoke. However, when the engine is hot, idle not obvious, heavy smoke (blue) while pressing the accelerator. I checked the spark plug, the 4 are roughly the same, dark but not wet.
Some people say broken piston ring, some people say valve stem seal,...
Any advice would be appreciated.
I have a Astra MK4. It has a strange probelm of burning oil. When the car just warmed up, the engine runs "no problem"---no blue smoke. However, when the engine is hot, idle not obvious, heavy smoke (blue) while pressing the accelerator. I checked the spark plug, the 4 are roughly the same, dark but not wet.
Some people say broken piston ring, some people say valve stem seal,...
Any advice would be appreciated.
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