Help me decipher my leak down test!!

[skree25]

I'm hoping there's a solution to this that doesn't require pulling the heads...

In the midst of doing a stage 3 build and 6MT swap on my 2001.5 Avant. Leak down test showed 9-13% on all cylinders except #3 which had ~32%. Air coming out intake manifold. The engine has been out of the car about a week and test was done on cold engine...

Do the heads need to come off and valves redone, or is there another option for diagnosing and fixing this?

Obviously I'd like everything to be tight an in-spec before the build. Are there more tests I can do to better identify what might be causing this? Car ran fine prior to engine pull.

[AudiTechS4]

you can pull the intake manifold and inspect valves . close the valves and pour a small amount of water in the intake valves and see if they bleed into the engine

[NOTORIOUS VR]

32% and air coming out the intake means the car wouldn't have been running fine before you started the upgrades.

I'm going to say cyl 3 wasn't at TDC completely and an intake valve was still partially open. Verify TDC on that cylinder properly and re-do the test.

[skree25]

Ok, so I pulled the valve cover just to be absolutely sure I was at TDC and reran the leak down test. Still show a bad leak out the intake. Then I did what AudiTech suggested and pulled the intake manifold to inspect the valves. Poured a little water in all three and all held water for only a minute or so. Then I reran the leak down test and very clearly the air was leaking past all three valves (the one furthest from the passenger was the worst, followed by the closest to passenger, then the middle).

I haven't done valves before so I'm not sure how to diagnose this. I can see the valves open/close as I turn the engine over, so I don't think any of them are stuck. It would be hard to believe that the springs or valves are worn since all the other cylinders/valves show very good compression. This engine had a head job done ~20k miles ago, is it possible the valves for this cylinder weren't installed correctly?

What should I do next?

[NOTORIOUS VR]

Well you have your answer... if it's leaking air @ TDC and not holding water, you have bent valves.

Time to pull that head.

[skree25]

I was afraid of that...

Wouldn't the car have been running like crap if I had bent valves? And how would I bend valves on only one cylinder?

Is it possible that something between the lifter and valve itself is not allowing the valve to seat and seal properly? Springs or seals?


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[blitz2190]

I was afraid of that...

Wouldn't the car have been running like crap if I had bent valves? And how would I bend valves on only one cylinder?

Is it possible that something between the lifter and valve itself is not allowing the valve to seat and seal properly? Springs or seals?


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it could be carbon if you have excess oil in the intake, or something got in there and messed up the seat but most likely a bent valve, have you brought it to the rev limit a lot? maybe floated a valve, and yeah its possible to bend only a few valves. how does the lifter look? mine had the center chewed out because of a worn lobe but other than that it may be time to pull the head.

[NOTORIOUS VR]

I was afraid of that...

Wouldn't the car have been running like crap if I had bent valves? And how would I bend valves on only one cylinder?

Is it possible that something between the lifter and valve itself is not allowing the valve to seat and seal properly? Springs or seals?


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Could be... either way you need to take the head off to find out so it really doesn't matter or worth speculating at this point.

[skree25]

I don't think its carbon build up. The heads were done fairly recently and everything still looks squeaky clean.

I'll take the exhaust cam off and check the lifters but from what I could see there didn't look to be any abnormal wearing.

I guess it's time to pull the head then...


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[ElementR]

As much as it sucks, pulling the head is the right thing to do based on everything you described. Clearly you have a valve sealing issue and only way you'll fix that is to address it on the head with it off the engine. I of course assume you are certain that the cam lobes were not compressing the lifters open at all. If you really want to convince yourself, pull the cam off and run the same leakage test. At that point there is no chance the cam would be holding the valves open.

[skree25]

As much as it sucks, pulling the head is the right thing to do based on everything you described. Clearly you have a valve sealing issue and only way you'll fix that is to address it on the head with it off the engine. I of course assume you are certain that the cam lobes were not compressing the lifters open at all. If you really want to convince yourself, pull the cam off and run the same leakage test. At that point there is no chance the cam would be holding the valves open.

Yes, that makes sense. I'll pull the intake cam off tonight--might as well rule out the only other option that doesn't require pulling the head. And besides I have to wait for the head bolt socket I ordered to come in...

[spacecadet]

that sucks man. good luck with repair. gonna pull both heads if its valves? 2.8 exhaust cam time?

[vavJETTAw36]

What could be wrong with the cam that would hold the valve open? That doesn't make sense to me.


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[NOTORIOUS VR]

Could also be a cracked valve, or heck a cracked head... only way to know for sure is the pull the head.

Certainly @ 32% leak down the engine would not be running completely round. But as with anything not everyone knows what/how a motor should really run.

I can hear loss of compression just by someone cranking their engine during start, most others wouldn't know what I am hearing to it's all relative.

[skree25]

that sucks man. good luck with repair. gonna pull both heads if its valves? 2.8 exhaust cam time?

No all other cylinders passed leak down test at 9-13% so I don't think there's any need to pull the other head. But it would be a good oppty to go to the 2.8 intake cams would make sense if I could find a good donor...

It always feels much better to do an "upgrade" than a repair...

[skree25]

Could also be a cracked valve, or heck a cracked head... only way to know for sure is the pull the head.

Certainly @ 32% leak down the engine would not be running completely round. But as with anything not everyone knows what/how a motor should really run.

I can hear loss of compression just by someone cranking their engine during start, most others wouldn't know what I am hearing to it's all relative.

Yes, the special head bolt socket tool should be here tomorrow pm, so I'll let you know what I find on Thursday hopefully...

Thanks for all the help!

[blitz2190]

2.8 intakes, the exhaust are the same

[ElementR]

What could be wrong with the cam that would hold the valve open? That doesn't make sense to me.


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Nothing wrong with cam.... cam not on base circle.

[vavJETTAw36]

Yes, the special head bolt socket tool should be here tomorrow pm, so I'll let you know what I find on Thursday hopefully...

Thanks for all the help!

What's this special tool you need for head bolts? I'll need one for my build


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[blitz2190]

https://www.amazon.com/Schwaben-Audi.../dp/B0055TBTG0 be sure to get the longer one like this, the short one can result in scaring a camshaft if your not careful, ask how i know :(

[ReggieNoble]

If you have an O'Reilly's auto parts near you, they stock polydrive bits for $10. Jus for a heads up

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[skree25]

https://www.amazon.com/Schwaben-Audi.../dp/B0055TBTG0 be sure to get the longer one like this, the short one can result in scaring a camshaft if your not careful, ask how i know :(

Did I make a mistake with this one? (the $7.50 price was so tempting...)

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[skree25]

2.8 intakes, the exhaust are the same

My DD is a 2.8, could I just swap intake cams between the 2.7 and 2.8?? Obviously would help the 2.7 but would it hurt my 2.8 much?

[ReggieNoble]

http://m.oreillyauto.com/h5/r/www.or...3182/N0716.oap This is what I got

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[blitz2190]

Did I make a mistake with this one? (the $7.50 price was so tempting...)

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Thats the one i used and ruined a cam, it works just be sure to pull away from the cam as you will need to pull the caps at the ends to reach the bolts exposing the bearing surface, it will really only show an improvement up top with bigger setups, and you would want upgraded valves to make use of them, as for the 2.8 it wouldn't be a huge difference, I'm going to go with a set of supertech springs when i do the swap to 2.8's.

[skree25]

Thats the one i used and ruined a cam, it works just be sure to pull away from the cam as you will need to pull the caps at the ends to reach the bolts exposing the bearing surface, it will really only show an improvement up top with bigger setups, and you would want upgraded valves to make use of them, as for the 2.8 it wouldn't be a huge difference, I'm going to go with a set of supertech springs when i do the swap to 2.8's.

Thanks for the heads up, I'll keep that in mind...

Yes, hopefully there's a complete bottom-end rebuild in this car's future which is when it'd make sense to just go with 2.8 heads altogether

[blitz2190]

Thanks for the heads up, I'll keep that in mind...

Yes, hopefully there's a complete bottom-end rebuild in this car's future which is when it'd make sense to just go with 2.8 heads altogether

careful, thats a steep rabit hole," once its built i get head, then i can get bigger turbos...." lol, once you start just take your time and do it right so your not in there again.

[S4James]

"may as well" is a quick way to spend 10 grand.

[NOTORIOUS VR]

"may as well" is a quick way to spend 10 grand.

Said a wise man once...

[skree25]

Well let's just "look" down the rabbit hole for a second...

I've got JHMs RS6-R turbos on there now. To fully utilize those all I'd need would be new rods right? The local machine shop that specializes in VAG said they won't upgrade rods without pistons and want $5k for the bottom end. Would it be stupid to just do rods and keep everything else as is? (Minus the bent valves) and shouldn't that be closer to $1500??


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[ElementR]

If your pistons are in good shape and all you need is a light hone and rings, then you can certainly save some money, but all the little things add up fast... bearings, new hardware, gaskets, timing belt set, water pump (should do that while you're in there). Ignore your heads, include price of new rods and consider reusing your pistons and you're still looking at $1500-2000 just in parts and depending how much of it you do yourself vs farm out another $500 to few grand in machine/assembly work. On the cheap end, that assumes no balancing of the crank, just pin fitting the rods and cleaning and honing the bock. Rest is all on you (gapping and installing rings), checking bearing clearances and installing bearings, assembly of pistons/rods/oil pump/mains/etc. How much you do yourself will come down to how much you know how to do or want to take the time to learn how to do, how much time you have and how good your tool arsenal is.

On the flip side, it's possible that after a hone on the block, your pistons are too small for the block (all it takes is one cylinder to need a decent hone and you need a whole new set). So many unknowns until you get into it.

And some will say just pop the rods/pistons out and R&R the rods and throw it back together. I would never go that route personally.

[spacecadet]

My DD is a 2.8, could I just swap intake cams between the 2.7 and 2.8?? Obviously would help the 2.7 but would it hurt my 2.8 much?

every junkyard around me is full of 2.8's. If your really interested I would think your local yard would have some donors too. i hope you get your stuff figured out ! i have a bad feeling i have bent valves too but my leak down is coming back fine, but maybe we are, in fact, bent valve buddies.

[NOTORIOUS VR]

The local machine shop that specializes in VAG said they won't upgrade rods without pistons

Get a new shop... if they truly specialized in VAG, they would know how good the pistons are in the 2.7T and wouldn't make a claim like that.

[blitz2190]

Well let's just "look" down the rabbit hole for a second...

I've got JHMs RS6-R turbos on there now. To fully utilize those all I'd need would be new rods right? The local machine shop that specializes in VAG said they won't upgrade rods without pistons and want $5k for the bottom end. Would it be stupid to just do rods and keep everything else as is? (Minus the bent valves) and shouldn't that be closer to $1500??


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Building the bottom end myself with all new parts, rpm rods, arp main studs, including timing belt kit mine came in around 2600 (closer to 3k if you need the tools) including a hone, balanced assembly, and having the rods checked and honed for my pins, done by a good machine shop local to me. I haven't begun building the heads yet. And yeah if they make that claim they don't know the 2.7.

[skree25]

It's Integrated Engineering out of Salt Lake so I assume they'd know the 2.7... but I'll do some shopping around. If I could get it close to $3k it'd be worth it


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[skree25]

And I pulled the intake cam this morning to make sure no issue with the lifter. Everything looked ok so I'll pull the head tonight and take some pics of what I find...


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[skree25]

Building the bottom end myself with all new parts, rpm rods, arp main studs, including timing belt kit mine came in around 2600 (closer to 3k if you need the tools) including a hone, balanced assembly, and having the rods checked and honed for my pins, done by a good machine shop local to me. I haven't begun building the heads yet. And yeah if they make that claim they don't know the 2.7.

Are you not doing piston rings since you're honing cylinders?


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[ElementR]

I'm sure he factored in rings even if not specifically listed. That cost sounds about right.

[ElementR]

It's Integrated Engineering out of Salt Lake so I assume they'd know the 2.7... but I'll do some shopping around. If I could get it close to $3k it'd be worth it


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IE should know this engine no doubt, but if your pistons are in good shape and you don't have to remove to much to clean up the cylinder walls, then they should be able to be used. Mahle made the OEM pistons. I have an aftermarket version in mine. I would have used the OEM pistons, but one of the cylinders in the block that I purchased for my build needed just a bit more than was safe to run factory piston so I went next size up with the Mahle Powerpack pistons. You generally won't know until you get into the engine. So factor $500-700 more for new pistons worst case and that considers that you offset some cost of not buying rings since they come with new pistons. You may also want to get the skirts coated if you re-use the pistons. The skirts have an anti-friction coating and chances are that it's worn down on the OEM pistons. It's a nominal fee vs new pistons.

[blitz2190]

Are you not doing piston rings since you're honing cylinders?


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yes, oem rings, sorry I didn't list everything but I replaced every bearing, washer, seal etc in the bottom end.And IE as in the major parts guys everyone uses? or another shop that also calls themselves IE? if its the first they definitely should know the engine as well as that the oem pistons are good pistons.