Most likely cause of low compression on an '01 1.9TDI

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

IIRC, you should have 475 psi. Something tells me that this car has been badly babied. Piston rings probably not seated. Sometimes, going through the Drivbiwire break-in procedure can rescue a car that's got low compression.

Drivbiwire break-in procedure: http://forums.tdiclub.com/showthread.php?t=48940

Although, that's REALLY low, even for a car that's been babied... but at 140k km, unless it's been really poorly treated otherwise...

You may want to get a second opinion. If you post your location, there are some very skilled TDI mechanics on this site that may be close to you.

Yes, please post your location (better yet, put in into your profile)...

Although I suspect you're in Canada, and on average, the Canadian VW dealers are a bit more at home with the TDI's than the ones you'll find in the U.S. (greater proportion of TDI's), many dealers still are far from the ideal place to have your TDI diagnosed...

If you're going to try the "drop of oil" compression test method, be extremely careful: if you get too much oil in there, the engine will hydro-lock and bend a rod or two...

Your compression should be in the high 400's (over 500 is nice)... It's possible to wreck the rings by using badly filtered air...

All the best,

Yuri.

Mine waas in the 530's at 100K acrossthe board. If they didn't run the car and get it hot before the test the results would be way off. But it does sound like the car is hosed. Bent valves maybe due to improper timing belt job.

Sorry, I thought my location was in my profile. I'm in Hamilton, Ontario, the dealer was Hamilton VW.

Thanks

Okay, well obviously something's wrong, including maybe the dealer compression test itself. But what I'm wondering, is what is the experience of this group, and what is the most probable?

Badly filtered air? Maybe, but it only has 140kkm on it, and VW recommends 60kkm air filter changes. (which seems long to me)

Bent valves? Yes could be, but only very, very slightly if they are because there is compression.

But does it seem reasonable in your collective experiences that one of these engines could be worn out (rings/cylinders) in 140kkm?

Mark

No. They just don'r wear out unless someone didn't change the oil or ran the wrong stuff.

More than likely carboned up rings from driving it like a Cummins...

Get the car back, change the oil to a VW 506.01 0w30 (similar to the break-in oil from the factory).

Inspect the turbo's compressor, if it looks good then the air filter was working and the cause is babying the motor.
Make sure the N75 is working.
Make sure the VNT actuator rod is cycling through its full range (use a hand vacume pump to verify this).
Contact Diesel Injection Service in Portland Oregon, have the pump rebuilt for around $500-600 plus shipping.
Also send them your injectors and have them pop tested at the same time! Bad injectors will kill cylinders as fast as dirt can.

Re-install the pump and injectors then:
One way to de-carbon the rings is to retard the timing to increase the cylinder temps, this bumps the temperatures of combustion enough to help burn off carbon buildup in the cylinders and turbo/VNT ring. I suggest just below the green line in VAC-Com but NEVER below the redline, I can say for certain this can and will melt the turbine wheel!

Get on a nice long stretch of road and in 5th gear floor it until it stops accelerating. Long bursts of high boost and fueling will heat things up and get the cylinder pressures up to where the rings will start to work free.

The last car I ran into this problem with took about 2 weeks of aggressive driving to get the compression back up. The cylinders finally leveled off around 480psi from 270ish in that period of time. Starting issues competely disapeared and I reset the injection timing to 70/110 at that point.

Bottom line make that turbo sing! If you can take a road trip(2-3 hours each way) and make constant bursts up to high speed to get the cylinder pressures working for you. If you are comfortable speeds of 90-100+ for 60 seconds work wonders and blowing out carbon...

Keep us up to date but I think the motor will come back to life.

DB
in HKG

Compression checks MUST be done with an engine at operating temperature, also it MUST be cranked until the pressure on the gauge STOPS rising at which time the values are recorded... Most dealers haven't a clue how to properly check the TDI compression.

Because of the long cranking cycles I always suggest having a battery charger hooked up to get uniform cranking speeds between checks.

Waiting at least 2-3 minutes between cylinders is a good idea to keep the starter from overheating plus it allows the battery to recover for good cranking speeds.

DB

Thanks for the good advice, Drivbiwire. Somewhat more useful than the 'the car is hosed'. I can see that carbon might be a problem, and I have heard of decarbonization of these engines. There is a place in Brampton near here which has special equipment to decarbonize TDIs without taking them apart. I don't know what chemical they use, or the brand of the equipment, but it's a relatively new system. The fellow I talked to there said that it requires an oil change afterwards, probably due to the stuff getting into the oil. Would that proceedure also help to clean out the rings?
I will also recheck the compression with a battery booster, and check the turbo as you said. What is the 'N75' btw? I can get the pump rebuilt by a Bosch authorized shop here for about the same price in cdn $, which I was planning to do, and they also do injectors.
The last oil change was ZVW-352-540-S. Will have to look into the break-in oil.

Thanks again,

Mark

DON'T DO IT!

If one tiny chunk of carbon gets into a valve, your car WILL be hosed! The intake manifold should come off of the car for cleaning.

Drivbiwire said:

Compression checks MUST be done with an engine at operating temperature, also it MUST be cranked until the pressure on the gauge STOPS rising at which time the values are recorded... Most dealers haven't a clue how to properly check the TDI compression.

Because of the long cranking cycles I always suggest having a battery charger hooked up to get uniform cranking speeds between checks.

Waiting at least 2-3 minutes between cylinders is a good idea to keep the starter from overheating plus it allows the battery to recover for good cranking speeds.

DB

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My suspicion is the dealership did this on a cold engine. Take it to a more competent shop and have it rechecked. If compression was that low, the car would be a complete dog! You would get run over by 3-year olds on tricycles.

There's a number of TDIclub members in the GTA IIRC and I'm sure someone would be willing to lend a hand if needed. Check out the regional forum and see if there are any upcoming GTGs

I hope he fixed it 5 years ago!

I had an engine replacement at 252525km in my 2001 Jetta 1,9 TDI AHF. The replacement engine had between 60000-80000km on it. I drove it for 1800km then had a blowout on the highway at 4000rpm at a speed of 180km/h. The engine cut out with a grey cloud of smoke behind me. Initial dash lights were battery and glow plugs. Pulled over and it started up with violent shudder on the engine. No knocking inside the engine though. But the glow plug light continued to flash. The car starts up as normal and idles at 800rpm but the engine still shudders with hardly any compression. Any thoughts on a diagnosis?

Which tire blew? Right front? Maybe took out the intake plumbing?

Bent rods due to sudden oil ingestion from the intercooler or turbo is the usual suspect when the engine suddenly belches a ton of smoke and then has weak compression.

Has a compression test been done? If so, any oil on the glow plugs?

Post from 2006, then revived in 2011, guys read the date before posting. I dont think OP is going to be posting results any time soon.

Maybe he means boost not compression. I think KLXD might be on the right track with the boost piping.

Mongler98 said:

Post from 2006, then revived in 2011, guys read the date before posting. I dont think OP is going to be posting results any time soon.

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Post #17, from today, restarts the thread with a new query.

Vince Waldon said:

Post #17, from today, restarts the thread with a new query.

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This is why people need to stop adding on to a thread that is old and start their own new one. They can post the link to the thread they want to point out in their post.

Cracks me up how this thread was ressurected three times. But I'll add on anyways, since I had some questions about tesitng compression, somewhat related to the original part of the thread.

Is it absolutely mandatory that the engine be up to operating temp before doing a compression test? And would it be okay to put a rag between each of the fuel lines and injectors, so I don't get fuel all over the place (even after disconnecting the fuel shutoff solenoid wire)? I did a boo boo and popped my compression gauge last week. Thankfully, that's why Harbor Frieght has such a good return policy. I'm not too worried about my Golf, but I am worried about my Ute. Light smoke at idle, even after coming up to operating temp, and if I'm doing things like slowly slipping the clutch when backing a trailer into place at the ranch, I get more smoke than with the Golf. I thought it was the injectors at first, but I've tried two sets of rebuilt injectors on that car with the same amount of smoke at idle.

Cracks me up how you abuse the tool then abuse HF's return policy.

You want an accurate test the engine should be hot. You want a quick and dirty maybe a rod is bent check then no.

jokila said:

This is why people need to stop adding on to a thread that is old and start their own new one. They can post the link to the thread they want to point out in their post.

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pkhoury said:

Cracks me up how this thread was ressurected three times. But I'll add on anyways, since I had some questions about tesitng compression, somewhat related to the original part of the thread.

Is it absolutely mandatory that the engine be up to operating temp before doing a compression test? And would it be okay to put a rag between each of the fuel lines and injectors, so I don't get fuel all over the place (even after disconnecting the fuel shutoff solenoid wire)? I did a boo boo and popped my compression gauge last week. Thankfully, that's why Harbor Frieght has such a good return policy. I'm not too worried about my Golf, but I am worried about my Ute. Light smoke at idle, even after coming up to operating temp, and if I'm doing things like slowly slipping the clutch when backing a trailer into place at the ranch, I get more smoke than with the Golf. I thought it was the injectors at first, but I've tried two sets of rebuilt injectors on that car with the same amount of smoke at idle.

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You can do a cold compression test, though the Bentley specs are for warm, and cold compression will be slightly different.
In my experience,I would not trust a harbor freight compression tester, as they are nowhere near accurate.
A compression check really never is a bad idea, but I would check the injector IQ and timing first.

KLXD said:

Cracks me up how you abuse the tool then abuse HF's return policy.

You want an accurate test the engine should be hot. You want a quick and dirty maybe a rod is bent check then no.

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Given all that crap is overpriced Chinesium, I don't have any remorse. And technically, it's not abusing the return policy, since I was honest why it failed, and the store clerk laughed and got me another one. I don't really have $500 for a Matco compression gauge, since I don't know how often I'd use it.

Ever used HF's air-powered brake fluid flush kit? It uses the crappiest brittle plastics. Mine failed on me after about a month (and 3 cars). HF staff straight up told me not to bring it inside, because DOT3 is somehow hazardous materials to them. I just got a refund right then and there.

Good to know on the engine being warm. One of these days, I'll try it then, though I'm not really wild about fiddling with fuel lines on a warm or hot engine. Learned my lesson, to pull the fuel lines from the injectors and turn over the motor a few times to be sure there's no fuel in the combustion chambers.

As for IQ - I was at 5.2 at idle. Left VCDS in the other car, so I used ColorMFA to show me measuring block 15, and then hammer modded down to 4.2 (the car was a lot more responsive at 4.2, anyways).

What you are looking for is consistency besides max compression.

Even if you read them cold, the amounts shouldn't deviate past a certain percentage. So doing it cold is fine to get some feel for the compression level. If a cylinder is bad, it will show up regardless of cold or warm. If you are looking for peak compression, a warm engine is the way to go.

jokila said:

What you are looking for is consistency besides max compression.

Even if you read them cold, the amounts shouldn't deviate past a certain percentage. So doing it cold is fine to get some feel for the compression level. If a cylinder is bad, it will show up regardless of cold or warm. If you are looking for peak compression, a warm engine is the way to go.

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Thanks. That actually makes a lot more sense, so I might go that route then. I am pretty concerned about my Ute. I compared last night - NO visible smoke just idling from my Golf, but the Ute idles like my IDI tractor (that I think might also have worn rings).