Anyone have any expereince with a burnt valve in their I-5?
10-12-2006, 08:09 AM
#11
I wouldn't replace the head, it's got hardened seats, so you could pop a new valve in it
That would be the cheapest fix. Remove the head and put in a new valve, hand lap it to get the seat mated up to the valve.
Of course the "correct" way would be to have a machine shop replace the guide, and then cut the seat in the head to match the valve.
But if you're going to go that route, you'll wind up doing all the guides and probably replacing all the exhaust valves and grinding the seats, replacing all the valve stem seals, etc. $500 later they'll be done with it and you can have your mechanic put it back on.
Depends on your finances I guess. If it were mine, I'd wack a valve in it and put it back on the road.
Of course the "correct" way would be to have a machine shop replace the guide, and then cut the seat in the head to match the valve.
But if you're going to go that route, you'll wind up doing all the guides and probably replacing all the exhaust valves and grinding the seats, replacing all the valve stem seals, etc. $500 later they'll be done with it and you can have your mechanic put it back on.
Depends on your finances I guess. If it were mine, I'd wack a valve in it and put it back on the road.
10-12-2006, 08:17 AM
#12
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Re: Anyone have any expereince with a burnt valve in their I-5?
Ray, I'm not a "certified ASME" mechanic,but with 35+ years of turning wrenches with 4 being for a local Nascar figure 8 champion, I have never seen a burnt valve due to prolonged storage. You need to do a compression check/cylinder leakdown test to see if this is your problem and quite frankly if your mechanics didn't do one and give you reading results, I would have my doubts about their diagnosis.
I have kept cars stored for years, put them back into use, and never had a "burnt" valve problem. Had a few "stuck" lifter problems and some "fuel" delivery problems. These Audi I-5 engines are extremely hardy and I think they may be leading you down the wrong path.
It's tough to do "online" but these are a few things I would consider before jumping into a "new" head.
When you first bought the car, how was the engine running and when did this rough running start? During the time you were driving the car was the engine exhibiting any louder than normal lubrication "knocks" or "pinging"?
You say your injectors get fuel but is the spray pattern a mist or a drip? Is the cylinder firing at all or is there no difference when you run with #4 plug wire removed? Do you have any lifter tap that seems louder than acceptable in these motors? Have you ever had the valve cover off, so as to see if the cam is possibly worn due to bad lubrication, on those valves?
That's not to say your mechanics diagnosis may not be right, but I would no way assume or believe that just because your car sat idle for a period of time, you will have a burnt valve after resuming normal use. If you have a valve train problem, it's cause would most likely be traced back to bad ignition timimng, low grade fuel use, or poor or lack of lubrication to the cam/lifter area or a combination of all these.
I have kept cars stored for years, put them back into use, and never had a "burnt" valve problem. Had a few "stuck" lifter problems and some "fuel" delivery problems. These Audi I-5 engines are extremely hardy and I think they may be leading you down the wrong path.
It's tough to do "online" but these are a few things I would consider before jumping into a "new" head.
When you first bought the car, how was the engine running and when did this rough running start? During the time you were driving the car was the engine exhibiting any louder than normal lubrication "knocks" or "pinging"?
You say your injectors get fuel but is the spray pattern a mist or a drip? Is the cylinder firing at all or is there no difference when you run with #4 plug wire removed? Do you have any lifter tap that seems louder than acceptable in these motors? Have you ever had the valve cover off, so as to see if the cam is possibly worn due to bad lubrication, on those valves?
That's not to say your mechanics diagnosis may not be right, but I would no way assume or believe that just because your car sat idle for a period of time, you will have a burnt valve after resuming normal use. If you have a valve train problem, it's cause would most likely be traced back to bad ignition timimng, low grade fuel use, or poor or lack of lubrication to the cam/lifter area or a combination of all these.
10-12-2006, 10:16 AM
#13
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Fault Isolation
If you HAVE isolated the problem cylnder, try swapping the injector with it's neighbour, and see if the problem moves with the injector. A bit easier than changing the head.. (Well, maybe not, if they haven't been out for in a while!)
(Injectors spray all the time, so it really doesn't matter what cylnder has what injector)
Similar to swapping injectors, trade two spark plug wires, and see if the problem moves, or swap two spark pugs and see if the problem moves.
But do only one change at a time befroe testing, or you won't have any idea as to what you have proven as a problem..
Compression test good idea too!
(Injectors spray all the time, so it really doesn't matter what cylnder has what injector)
Similar to swapping injectors, trade two spark plug wires, and see if the problem moves, or swap two spark pugs and see if the problem moves.
But do only one change at a time befroe testing, or you won't have any idea as to what you have proven as a problem..
Compression test good idea too!
10-12-2006, 10:32 AM
#14
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This part we did.
The swap of both wire and injectors has been done. Even r/r the injector seals on cyl 3 and 4. Swapped wires as well. Problem definately resides w/ cyl #4.
10-12-2006, 10:50 AM
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This car ran absolutely fine before I "retired" it to do the stuff I've done. long>>>
It looked like ****, however it ran really really well, w/o undue lifter noise, or poor mileage. Got 26mpg all the way home from Ohio even with [admit this embarrasingly] running it at interstate speeds w/ rear brakes so shot that it was just grim.
Spray pattern is a mist, however not as fine a mist as a new one. BTW, 196,xxx miles on the engine.
Rough running started about a month ago, maybe three weeks. Timing is NOT the prob, that's just fine. Car sounds a bit like a bandsaw going down the road, and has poor accelleration at this time. However once it's up to speed, it runs just fine. mileage has dropped to around 18-20mpg, when it should be really really great given all the stuff that has been done to it. NO knocking or pinging a'tall. Just ****ty running and mileage. I run 87 octane in this engine, other octanes do not seem to matter to it.
I had my mechanic r/r the valve cover gasket, 'cause I was too lazy to do it myself at the time. he was up in there anyway, doing the timing belt. Inmy defense, I was involved with lots of other stuff on the exterior of the car at the time. So, I personally have not seen what the valves look like under there. I'm going to soon, tho, as am "reasonably doubted" at this point about the condition of everything under that cover... by the commentary by your guys here. Especially since the car ran sooooo good previously.
BTW, the old boy starts up immediately when the key is turned. I am disinclined to think I've a bad cylinder in there.... every car I've every had that had a cyl going was 'way more noisy and a beast to start.
Spray pattern is a mist, however not as fine a mist as a new one. BTW, 196,xxx miles on the engine.
Rough running started about a month ago, maybe three weeks. Timing is NOT the prob, that's just fine. Car sounds a bit like a bandsaw going down the road, and has poor accelleration at this time. However once it's up to speed, it runs just fine. mileage has dropped to around 18-20mpg, when it should be really really great given all the stuff that has been done to it. NO knocking or pinging a'tall. Just ****ty running and mileage. I run 87 octane in this engine, other octanes do not seem to matter to it.
I had my mechanic r/r the valve cover gasket, 'cause I was too lazy to do it myself at the time. he was up in there anyway, doing the timing belt. Inmy defense, I was involved with lots of other stuff on the exterior of the car at the time. So, I personally have not seen what the valves look like under there. I'm going to soon, tho, as am "reasonably doubted" at this point about the condition of everything under that cover... by the commentary by your guys here. Especially since the car ran sooooo good previously.
BTW, the old boy starts up immediately when the key is turned. I am disinclined to think I've a bad cylinder in there.... every car I've every had that had a cyl going was 'way more noisy and a beast to start.
10-12-2006, 11:53 AM
#16
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Someone told me that these valves have >>>
"shims"... It was the other audi mechanic, not my usual guy...
This is the first I've heard of that. Can you shed some light on this?
This is the first I've heard of that. Can you shed some light on this?
10-12-2006, 11:58 AM
#17
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Re: This car ran absolutely fine before I "retired" it to do the stuff I've done. long>>>
OK so you know it's cyl 4, that's a start. Assuming your compression is good ( starts right up ) I would get a can of silicone spray, or carb cleaner and with the engine running, using the little tube thingy they give you, spray around the intake manifold where it contacts the head and listen for any changes in engine speed and running.
A BIG DISCLAIMER : most of these sprays are flammable and the exhaust will be hot and you need to be cautious and prepared for any flare ups.
Using the aiming tube you can spray and not have to worry about hitting the exhaust if you are careful.
Any change in engine speed will be an indicator of a bad gasket.
A BIG DISCLAIMER : most of these sprays are flammable and the exhaust will be hot and you need to be cautious and prepared for any flare ups.
Using the aiming tube you can spray and not have to worry about hitting the exhaust if you are careful.
Any change in engine speed will be an indicator of a bad gasket.
10-12-2006, 12:26 PM
#18
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Some older Audi motors had 'sold' lifters..
Some older Audi motors had 'solid' lifters (Like the early urq).
Those motors needed the valve lash (slack) adjsuted by inserting different thickness shims (round discs) under the lifters. Painful too adjust, as I think you have to pull the camshaft. Solid lifers are supposed to be able to deal with high revs better..
However, the JT motor uses hydraulic lifters, that automatically take up any valve lash (slack). (Unless, of course, you are low on oil, and you hear the ticking, because all the slack isn't taken up). No shims required.
However, low oil pressure will INCREASE your valve lash, not make it too small.
If you have too little valve lash, it's possible that a valve won't close properly, and then it will get burt very quick.
But as we have hydraulic lifters & no shims to mess with, we shouldn't have that problem. (Thank goodness!)
Unless something really quirky happend to a lifter, and it's jammed up or something, I doubt that's your problem.
Those motors needed the valve lash (slack) adjsuted by inserting different thickness shims (round discs) under the lifters. Painful too adjust, as I think you have to pull the camshaft. Solid lifers are supposed to be able to deal with high revs better..
However, the JT motor uses hydraulic lifters, that automatically take up any valve lash (slack). (Unless, of course, you are low on oil, and you hear the ticking, because all the slack isn't taken up). No shims required.
However, low oil pressure will INCREASE your valve lash, not make it too small.
If you have too little valve lash, it's possible that a valve won't close properly, and then it will get burt very quick.
But as we have hydraulic lifters & no shims to mess with, we shouldn't have that problem. (Thank goodness!)
Unless something really quirky happend to a lifter, and it's jammed up or something, I doubt that's your problem.
10-12-2006, 12:57 PM
#19
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Re: Some older Audi motors had 'solid' lifters..
The increase in valve lash will also cause the valve not to open fully which could give you rough running also.
My online diagnosis would be to look at the easiest first, do the compression test, remember to check the ring seal also by adding a squirt of oil in the cylinder bore and see if you get significantly higher readings after the first "dry" test.
Second, bad intake gasket causing vacuum leak and lean burn causing a cylinder imbalance( roughness) , carefully try the silicone leak find test.
Third, check the lifters and cam for wear, this is a little harder to do. Use a feeler gauge to check initial clearances, try to push down on the lifter caps and see if the clearance gets bigger. Visually look for any signs of severe wear on the cam.
Email if you need any other info but use this address:
"aljohnson@tmail.com"
Good luck, also I have a KX head if you need it.
My online diagnosis would be to look at the easiest first, do the compression test, remember to check the ring seal also by adding a squirt of oil in the cylinder bore and see if you get significantly higher readings after the first "dry" test.
Second, bad intake gasket causing vacuum leak and lean burn causing a cylinder imbalance( roughness) , carefully try the silicone leak find test.
Third, check the lifters and cam for wear, this is a little harder to do. Use a feeler gauge to check initial clearances, try to push down on the lifter caps and see if the clearance gets bigger. Visually look for any signs of severe wear on the cam.
Email if you need any other info but use this address:
"aljohnson@tmail.com"
Good luck, also I have a KX head if you need it.
10-12-2006, 02:51 PM
#20
Just for the record, there's really no reason to swap parts.
When you have a dead hole, you do a compression test....hot and with the throttle plate(s) wide open, cranking until the gauge stops reading any higher. If the cylinder has good compression, you know it's not internal.
If the cylinder has poor compression, you add a bit of oil to it and repeat. If the compression comes up alot, you know you have bad rings. If the compression does not change, you know you've got a bad valve. It's the exhaust valves that fail due to heat, but a leak down test will confirm this.
If the cylinder has poor compression, you add a bit of oil to it and repeat. If the compression comes up alot, you know you have bad rings. If the compression does not change, you know you've got a bad valve. It's the exhaust valves that fail due to heat, but a leak down test will confirm this.