yhmtdi
Well-known member
Hi, I'm new to this site, and although I've had VWs for 20years now, none have been diesel. My last one which I still drive, is a '90 GTI 8V with over 420,000km on it, and it's still strong, and burns no oil.
I recently picked up an '01 Golf TDI with 140,000km on it, and had it in to the dealer to check for fault codes (CEL on), test compression and set the injection pump timing, because it has been a little hard to start, but not too bad. Anyways, they did the compression test, and said it's 255psi on all four cylinders. Spec'd min according to Bentley is 276, with 'new' being 360-450psi. They also said the pump timing could not be set because the pump was worn out (noisy). The only fault codes are: glow plugs, coolant temp sensor, and EGR. I can deal with those. And if the pump is worn out, taking it off and getting it rebuilt isn't a problem either. But it's the low compression that's surprising, given the mileage on the car. (the car looks far from being abused btw). And the car seems to have decent power when driven too. So I'm not sure if I completely believe the dealer's numbers.
So here's my question for those of you with experience with diesels: What is the most likely source of low compression on these engines? Piston rings/cylinders? Or could this be caused by carbonization/valves? Given that it's even across the cylinders, that pretty much rules out the head gasket.
They didn't actually do a leakdown test, to pinpoint the cause. (and they didn't even call to ask about doing one once they'd measured the compression) So I'm thinking of doing the compression test myself (if I can find an adapter for the glow plug hole), and trying the 'drop of oil' method to check the rings as a start. Does it seem possible that one of these engines could be worn out at 140000km??
Thanks for your input, and an excellent site btw, with lots and lots of good technical info.
Mark
I recently picked up an '01 Golf TDI with 140,000km on it, and had it in to the dealer to check for fault codes (CEL on), test compression and set the injection pump timing, because it has been a little hard to start, but not too bad. Anyways, they did the compression test, and said it's 255psi on all four cylinders. Spec'd min according to Bentley is 276, with 'new' being 360-450psi. They also said the pump timing could not be set because the pump was worn out (noisy). The only fault codes are: glow plugs, coolant temp sensor, and EGR. I can deal with those. And if the pump is worn out, taking it off and getting it rebuilt isn't a problem either. But it's the low compression that's surprising, given the mileage on the car. (the car looks far from being abused btw). And the car seems to have decent power when driven too. So I'm not sure if I completely believe the dealer's numbers.
So here's my question for those of you with experience with diesels: What is the most likely source of low compression on these engines? Piston rings/cylinders? Or could this be caused by carbonization/valves? Given that it's even across the cylinders, that pretty much rules out the head gasket.
They didn't actually do a leakdown test, to pinpoint the cause. (and they didn't even call to ask about doing one once they'd measured the compression) So I'm thinking of doing the compression test myself (if I can find an adapter for the glow plug hole), and trying the 'drop of oil' method to check the rings as a start. Does it seem possible that one of these engines could be worn out at 140000km??
Thanks for your input, and an excellent site btw, with lots and lots of good technical info.
Mark