# Wet compression test. *Car now fixed* :)



## mk2506 (Feb 23, 2020)

I've read a teaspoon of oil is enough, but just want to be absolutely sure. A teaspoon is 5ml so I'm intending to inject 5ml from a syringe, for accuracy.

I'm aware of stories of hydro locking by using too much oil, but is 5ml absolutely enough for an accurate assessment of whether it's a valve prob or the dreaded piston prob? Seems a very small amount. Also, any other tips I should know of before doing this?


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## SwissJetPilot (Apr 27, 2014)

Not sure about a wet test, I've always done it dry. Here's a good YouTube on a compression and leak test. It's really important that you have a good quality set of gauges and not some cheap POC from China -

*Catastrophic Piston Failure 2.0t TSI Engine ~ Walkthrough and Diagnosis*


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## IPG3.6 (Sep 5, 2015)

Have you already tested dry?

If the reading is off you try wet - this can help tell you if the piston rings are the issue.

5ml seems a little BUT when you think about it the rings would normally be pushed up against the cylinder walls to create (mostly) a seal which allows for air and fuel to compress. It is only a few mm between piston rig end gaps and those are staggered to help create a better seal and less blow by. Once the rings are worn too much this seal against cylinder walls can be compromised and "loose" - when doing a wet test this is the space the oil takes - you don't need much due to tight tolerances in an engine.


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## mk2506 (Feb 23, 2020)

SwissJetPilot said:


> Not sure about a wet test, I've always done it dry. Here's a good YouTube on a compression and leak test. It's really important that you have a good quality set of gauges and not some cheap POC from China -
> 
> *Catastrophic Piston Failure 2.0t TSI Engine ~ Walkthrough and Diagnosis*


Yeah bought a Laser gauge for 60 quid, prob nowhere near the most expense gauge but should be ok for all that I'll use it for. Yeah those Chinese things look like toys ffs.


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## mk2506 (Feb 23, 2020)

ianpgonzaga said:


> Have you already tested dry?
> 
> If the reading is off you try wet - this can help tell you if the piston rings are the issue.
> 
> 5ml seems a little BUT when you think about it the rings would normally be pushed up against the cylinder walls to create (mostly) a seal which allows for air and fuel to compress. It is only a few mm between piston rig end gaps and those are staggered to help create a better seal and less blow by. Once the rings are worn too much this seal against cylinder walls can be compromised and "loose" - when doing a wet test this is the space the oil takes - you don't need much due to tight tolerances in an engine.


Yeah it was dry tested whilst getting the ECU checked (garage beside the auto spark) but then the lockdown kicked in and mechanics closed up. The paranoia is getting to me and at least I'll know if it's a piston by checking it wet.

It was 12 12 12 09 dry praying it's a valve or spring, or it's most likely toast if piston work is on the cards [smiley=bomb.gif]


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## IPG3.6 (Sep 5, 2015)

K. So definitely compression is down on 4.

Best thing to do now is a leak down test. This can help you find where the issue is (rings, valves or head)

What bad/strange incident happened prior to you bringing it in for compression checks?


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## mk2506 (Feb 23, 2020)

It had a misfire on cyl4 which eased from very rocky on cold idle to barely noticable at full operating temp. Seems to me metal is expanding somewhere to fill a gap. No classic head gasket symptoms like mixing oil/coolant.car drives perfectly otherwise.


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## mk2506 (Feb 23, 2020)

Well, I've just done it and cyl 4 went from 162.5ish dry to 177.5ish wet

All other cylinders are 180 - 182.5ish dry

Is that enough of a jump to indicate ring failures, or should there have been a big difference? Bear in mind that it's a BWA which are know for oil consumption due to rings, so possibly within scope??


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## IPG3.6 (Sep 5, 2015)

I'd say replace the engine or service the rings.

You're already noticing a significant performance drop. The pressures should be within each other's figures. #4 is an outlier. The engine no likey and it's showing up as errors. So. Yes. Something is "wrong enough" that you're noticing it and the computers are picking it up too.

It'll only get worse. (Sorry to be the bearer of bad news but ... I'm not going to lie)


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## mk2506 (Feb 23, 2020)

ianpgonzaga said:


> I'd say replace the engine or service the rings.
> 
> You're already noticing a significant performance drop. The pressures should be within each other's figures. #4 is an outlier. The engine no likey and it's showing up as errors. So. Yes. Something is "wrong enough" that you're noticing it and the computers are picking it up too.
> 
> It'll only get worse. (Sorry to be the bearer of bad news but ... I'm not going to lie)


I'm guessing replacing rings is going to be crazy money, even at an independent garage?


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## IPG3.6 (Sep 5, 2015)

Well it's a ton of work ...

Then it depends what they find is the cause that might increase the bill more. Might be a good consideration to get a bore scope (small insertable camera) to have a look inside #4 to see if there's damaged to the block.

Good luck.


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## mk2506 (Feb 23, 2020)

There was no sign of oil on the spark plug and no smoke out the exhaust and car still pulls like a train, it's a sickener


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## mk2506 (Feb 23, 2020)

After a quick look around engines are 1500-2000, I think a rebuild might be the option as the car is immaculate in and out (only saving grace for it atm), I'd be loathe to stick an unknown quantity engine in and find out it's as bad. Only issue with rebuilding is who's doing it! Rep of Ireland has no car scene at all hence no specialists, may have to take it up home to NI. Had only just spent 500 on a new timing belt kit before the lock down as well as 600 on tyres [smiley=bigcry.gif]


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## Iceblue (Jul 20, 2018)

Sorry to hear about your issue and hope you get it resolved. If it is cactus you should be able to buy a reconditioned motor with some kind of warranty. As a matter of interest what is your mileage and what has been your oil consumption prior to you noticing the problem at idle.


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## mk2506 (Feb 23, 2020)

72000 miles
Uses around 1tr over 700-800 miles

Not a lot of daylight between engines and rebuilds as far as I can see tbh, unknown quantities 1500-2000, I'd rather have it rebuilt and know it's a 100% strong engine. I wish this damn lock down was done with so I can get a mechanic to verify it's def rings. Seems cyl4 is a popular cyl to go down, as opposed to the other 3, there are so many posts on cyl4 probs over forums. Has to be a common link???

Can't believe I've been caught with a lemon, dealer will be speaking to my solicitor asap!


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## Iceblue (Jul 20, 2018)

mk2506 said:


> 72000 miles
> Uses around 1tr over 700-800 miles
> 
> Not a lot of daylight between engines and rebuilds as far as I can see tbh, unknown quantities 1500-2000, I'd rather have it rebuilt and know it's a 100% strong engine. I wish this damn lock down was done with so I can get a mechanic to verify it's def rings. Seems cyl4 is a popular cyl to go down, as opposed to the other 3, there are so many posts on cyl4 probs over forums. Has to be a common link???
> ...


I know it is a long shot but that kind of oil consumption may have passed audis engine replacement test. See attached and I know of one recently being replaced on this forum in the UK but obviously depends on all the circumstances. There is nothing to lose by you taking the car in for an oil consumption test at an Audi dealer. If they pick up the low compression on cyclinder 4 you could argue that is the fault of their sub standard pistons which is the reason for the high oil consumption.


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## Iceblue (Jul 20, 2018)

These are the threads from the person who had theirs replaced by audi recently
https://www.ttforum.co.uk/forum/viewtopic.php?f=19&t=1932769
https://www.ttforum.co.uk/forum/viewtopic.php?f=19&t=1943371


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## mk2506 (Feb 23, 2020)

Cheers, yeah saw a few cases of Audi contributing towards repairs. The car just had a dealer stamp 'history' with no proper receipts, in fact I have amassed more of a proper history in my ownership. Wouldn't Audi demand a full SH from their main dealers?

I flagged it with the trader I bought it from and the warranty company as it expired 2wks after lockdown, warranty company said they stand over any possible claim when I get it fully assessed, but they only cover up to 750. The trader is a right b******d and I know I'll have to get a solicitor involved to try force him into covering the excess.


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## IPG3.6 (Sep 5, 2015)

Man.... good luck with your solution.

To me - the easiest way out of this is a replacement, low mileage, known working engine. I've noticed the UK has a plentiful supply of engines and remember you can look into VW's, SEAT's and Skoda's for a replacement engine...

Why? To get to the stage where the piston is able to be removed you've got to dismantle SO much that you might as well swing an engine in and be done with it.

For example - *to replace the rings you must remove* (and this is simplifying the process...)
- all intake and turbo/exhaust piping 
- head (replace all torque to yield bolts and head gasket)
- driveshafts (again replace all TTY bolts)
- gearbox
- remove oil pan
- remove crank (again replace all TTY bolts plus bearings)
- finally you can get to removing pistons (where you need new rings all around.... you typically don't just do the one cylinder at this point)
- if there is damage to the block then you need a new block.... where you might as well have just swung a low mileage engine in.
All of the small, non reusable bolts and gaskets add up! Especially if sourcing from a dealer. Then you add in break in oils, before you use normal running oil where you must change your oil filters each time with each break in oil change. Again, adding up on the total
- go back from where you came from & top up fluids

Now *- to replace the engine (with a known low mileage engine)*
- all intake and turbo/exhaust piping 
- remove driveshafts (replace TTY bolts)
- remove engine and gearbox assembly (replace TTY bolts)
- attach replacement engine to your gearbox
- swing it all back in
- go back from where you came from & top up fluids

That's my 2c


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## mk2506 (Feb 23, 2020)

I know man but imagine getting another engine for it to throw up problems again. I cant find any TFSI engines under 1500. I wonder how many were trashed now that we know they suffer with catastrophic failures due to carbon build ups etc?!

If I can resurrect the engine for 1200-1500 then I'll go for the rebuild, if not, that trader won't know what hit him, that wasn't just an overnight fault :x


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## IPG3.6 (Sep 5, 2015)

good luck on getting quoted up and look forward to updates.


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## mk2506 (Feb 23, 2020)

I know, minimum 18th of May before mechanics even start up again and very possibly longer, it's crap not being able to get exact quotes!

Would a TTS lump go straight in, if it comes to getting another engine? ECU change?


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## IPG3.6 (Sep 5, 2015)

Not sure what your car is currently but yes a TTS engine will physically bolt up.

If the engine is not already a TTS one you will need to make sure it's complete with injectors, turbo, downpipe, boost piping and ecu to make the most of it.

The ecu also needs to be coded to your cluster / keys.


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## Iceblue (Jul 20, 2018)

mk2506 said:


> Cheers, yeah saw a few cases of Audi contributing towards repairs. The car just had a dealer stamp 'history' with no proper receipts, in fact I have amassed more of a proper history in my ownership. Wouldn't Audi demand a full SH from their main dealers?
> 
> I flagged it with the trader I bought it from and the warranty company as it expired 2wks after lockdown, warranty company said they stand over any possible claim when I get it fully assessed, but they only cover up to 750. The trader is a right b******d and I know I'll have to get a solicitor involved to try force him into covering the excess.


A dealer stamp history is something Audi can follow up with the relevant dealer. The key thing is to show it has had regular servicing within their recommendations which are not onerous. The point is they recognise there were some issues with some BWA's and post facelift (as in the thread above) but it is not widespread from what I have researched, and your car is well below a worn out engine in terms of miles. As I said you have nothing to lose.

I would not recommend legal action against a little guy trader post Covid given cost, grief and you may be going after a man of straw.

A TTS engine would be great but it may have had more chance of being thrashed than the base so any purchase of a 2nd hand unreconditioned engine will be a risk without recourse.


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## mk2506 (Feb 23, 2020)

ianpgonzaga said:


> Not sure what your car is currently but yes a TTS engine will physically bolt up.
> 
> If the engine is not already a TTS one you will need to make sure it's complete with injectors, turbo, downpipe, boost piping and ecu to make the most of it.
> 
> The ecu also needs to be coded to your cluster / keys.


Just base 2.0TFSI


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## mk2506 (Feb 23, 2020)

Iceblue said:


> mk2506 said:
> 
> 
> > Cheers, yeah saw a few cases of Audi contributing towards repairs. The car just had a dealer stamp 'history' with no proper receipts, in fact I have amassed more of a proper history in my ownership. Wouldn't Audi demand a full SH from their main dealers?
> ...


That's his problem, this all started fairly soon after I bought it, he obviously wiped faults and reset the ECU. He's being an a****** about it so he's getting what he deserves and will be going to court no matter what, find it strange you'd pity what's little more than a thief? He was quite happy to take 7K off me.

What kind of prices are TFSI/TTS engines over the water, I see some on eBay but surely there's others that don't advertise there?


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## Taylortony (Feb 10, 2012)

A cylinder wall has micro scratches on it to retain oil and help form a seal with the rings, often when you have a cylinder down this can be because the cylinder in question was the one on the compression stroke and the fuel air mix washes that oil layer off the walls. hence you do a wet test to re-establish that sealing capability.

Aircraft engines we do a compression test every one hundred hours, low compressions can often be caused by several factors, glazed bores where the oil has burnt on and filled the micro scoring preventing a good seal, rings chattering and aligning, ( each ring stage is normally installed 180 degrees from each other to form a good seal), it's not unheard of for them to align. wear.

what we do is remove individual cylinders, check the bores and rings for wear, replacing any ring sets that fail, clean carbon out of the ring groves, glaze bust the cylinder if serviceable and reinstall it. this is what we use to glaze bust

https://www.buncerental.com/equipment.a ... y=115-2410

To be honest I still cannot see why that would be causing your misfire especially if the plugs are not fouling and I take it the oil isn't black ( A sign of blowing past the rings).


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## mk2506 (Feb 23, 2020)

Taylortony said:


> A cylinder wall has micro scratches on it to retain oil and help form a seal with the rings, often when you have a cylinder down this can be because the cylinder in question was the one on the compression stroke and the fuel air mix washes that oil layer off the walls. hence you do a wet test to re-establish that sealing capability.
> 
> Aircraft engines we do a compression test every one hundred hours, low compressions can often be caused by several factors, glazed bores where the oil has burnt on and filled the micro scoring preventing a good seal, rings chattering and aligning, ( each ring stage is normally installed 180 degrees from each other to form a good seal), it's not unheard of for them to align. wear.
> 
> ...


Yeah there's absolutely no telltale signs like an oily plug etc, no smoking from the exhaust. All plugs were an even light tan and are in around 2000 miles. Changed oil last week for first time so can't really comment on it until it's done a few miles, but was just the same shade of black as any other 3000+ mile oil I've ever taken out of any car/bike, there was the faintest smear of 'mayo' under the cap when I topped up the new oil oil but a short trip could do that I've read.

I think I'll redo the test as it was my first time doing one, and pay attention to what cyl 3 looks like as it had a tiny diff compared to 1 and 2, just to rule out any possible head gasket leak between 3 and 4. It's the fact that something is def sealing up 90% compared to cold start and up to full operating temp that gives me a tiny bit of hope!

the more I research this the more I'm seeing cyl 4 being a problem on these engines regarding misfires, I wonder is fuel rail pressure a common problem possibly contributing to bigger problems??


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## Iceblue (Jul 20, 2018)

mk2506 said:


> Iceblue said:
> 
> 
> > mk2506 said:
> ...


I am not taking pity on a thief but rather giving you the benefit of my legal litigation experience (ex litigation solicitor). Matter for you if you want your day in Court but when you add up the cost/benefit it often does not make sense. This could be exacerbated by the post Covid environment.


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## mk2506 (Feb 23, 2020)

Just small claims court to make him cough up any excess not covered by warranty claim, costs are small for me to do that.


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## Iceblue (Jul 20, 2018)

Fair enough, if the terms of the warranty covers that damage and you can prove that it existed over the period covered by the dealers warranty. I suspect that if you are successful under the dealer warranty, the damages will be limited to the purchase of a reconditioned used motor if it is less than repairing your existing one. If you claim via audi you may get a brand new engine. Long shot I know but good luck with it all and keep us posted.


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## mk2506 (Feb 23, 2020)

And..........the culprit was just a broken lifter all along!! Happy to be only out 400 

Wet tests are NOT automatically a piston ring problem if compression increases, thank goodness!


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## IPG3.6 (Sep 5, 2015)

finally got the the bottom of it! good job - now have fun!


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## mk2506 (Feb 23, 2020)

Yeah, I was bricking it in case it was an engine write off!

Cheers, I intend to!


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## Taylortony (Feb 10, 2012)

Told you i doubted the rings were doing it  Glad its sorted.


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## mk2506 (Feb 23, 2020)

Taylortony said:


> Told you i doubted the rings were doing it  Glad its sorted.


 This man knows the score :wink:


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