Compression loss on 2007 A4 2.0t

[RickV]

Hello everyone, I could really use some help.
I just purchased a 2007 A4 Quattro Cabriolet automatic b7 with 116k miles that has engine problems. The previous owner says it was working fine but then it just stopped and the engine light came on. I checked the codes and these two came up, p0343 and p000a. The engine will crank but not start.
I was originally hoping it would be a faulty sensor or something minor since I saw the timing belt was changed at 96k miles but after doing a compression check that's not the case. My compression readings are as follows:
Cylinder 1 - 0
Cylinder 2 - 100
Cylinder 3 - 60
Cylinder 4 - 0
I then added a cap of oil to each cylinder and tried it again and found that cylinder 1 and 2 stayed at 0, cylinder 2 stayed the same and cylinder 3 went up to 105. Correct me if I'm wrong but since it's a straight 4 I don't think those results look like the timing belt slipped. I called some local mechanics and they all said they only replace the engines since they're too complicated to work on. Is that common practice on these engines or do I just have lazy mechanics near me?
I was hoping I could repair the engine but I'm not a mechanic and not sure what I should do next. I read about doing an air pressure test to see where the leak is and was wondering if that's the next step or if there's something else I should try? Thanks for any help, it's much appreciated. 🙏

[GIACuser]

It is not true that these motors are any more complicated than any other contemporary 4cyl motors. Rebuilding it does take a lot of labor hours and ties up a mechanic so he cannot work on other cars, and it doesn't always go smoothly so some shops just don't want to deal with the possible issues and if they are a small shop they don't want to devote a lot of time to it at and possibly delay other customer outcomes.

I don't mean to insult you but have to ask. Are you familiar with the process of performing a compression test. By that I mean, you are rotating the crank to the proper position as you do the check on each cylinder. If those are true readings that indicates some major trauma. Or you didn't do the test right and you need to go back and do it right before you make any decisions.

So assuming this compression test was done correctly then here is some info for you.

1. Since I assume you are not doing the work yourself, rebuilding the existing motor would be quite expensive.
2. If there is block damage the engine may not be a candidate for rebuild.
3. Taking apart the motor to see damage and find out if it is a candidate for rebuild would be expensive and you run risk of spending a lot of money only to find out bad news.
4. The real problem is that a solution will cost more than this car is worth. Generally they get totaled at this point or bought by someone who can provide the labor and do all their own work.

It would probably cost 5K or more to buy a used motor and pay to have it installed. This is a 16 year old car and there are engines available but not likely any low mileage ones.

It is time to walk away from this and take your losses. If not, be ready to put a bunch of money into it knowing you will be upside down financially and that this is an old car and there are other parts like the trans that could fail as well. It can very quickly become a money pit. And you could find yourself looking back and wishing you had put all that money into a newer car.

[RickV]

Hi and thanks for the reply. I honestly didn't know I had to rotate the crank in a specific way. When I did the compression check I pulled the fuse on the fuel pump, then I went to cylinder 1, unscrewed the spark plug and screwed my gauge in. I then turned the key and let it crank 4 times and then wrote down that reading. I put the plug back in and went to cylinder 2 and so on. Is this incorrect?
I bought the car because it was very cheap and the guy just dumped thousands into it. He put an entirely new convertible top and motor for the top in. A new battery, all new wheels and tires, new motor mounts and rebuilt the suspension too. The car is in perfect condition inside and out also. I was kind of hoping I could just put 1 or 2k into getting the engine working and have a decent first car for my daughter. Not a lot invested in case she goes hitting curbs and things. 🤷*♂️
Where I think I'm at is like what you said, do I put money into finding out if the engine can be saved or do I just put a new used engine in it. I was quoted $4000 to replace it with one that has 90k miles on it. I would just like to know as cheap as possible if this engine can be saved or if it's done.

[GIACuser]

Actually that will work for straight compression test. Rebuilding the motor will cost way more than putting in a used one and like I said you could get it apart and find it is unusable.

If you buy that motor, be sure and have them do the timing belt replacement (get a kit). Put in a new water pump, thermostat. New fuel pump cam follower. And consider replacing coolant lines or vacuum lines that look sketchy. I would also put a new set of coils and spark plugs in. Coils are a common point of failure. And do a compression test on the motor before you buy it..

Timing belt service at about that mileage is normal procedure. If that belt fails the valves can come in contact with the pistons and the motor can self destruct. Cam follower for fuel pump is an inexpensive piece but if it wears through the resulting damage can be extensive.

Kits I would install before you put that motor in car:

• Cam chain - LINK
• Timing Belt - LINK
• Thermostat - not included in timing belt kit above - LINK
• HPFP cam ollower - LINK

[RickV]

Ok and thanks for the great info. I'll definitely change out those parts if I do change engines. If I do a leak down test and find out that just the rings are bad do you think it's worth just replacing the top end?

[RickV]

Or what I'd really like to know is if it's possible the timing belt slipped 1 tooth and that would then cause the compression readings that I got? Maybe it's worth it for me to pull the front end off and inspect the timing marks? If it did jump time I don't think any major damage would have been done because there's no marks on top of the pistons showing they hit anything.

[GIACuser]

Leak down test is a test of how long a cylinder will hold compression. Your cylinders all have issues and only 2 are making some compression.

Remember that timing belt kit I mentioned. My guess is that your timing belt broke. This FSI motor is an interference motor so if the belt breaks the valves can come in contact with the pistons. My feeling is that you probably have a bunch of bent valves which is usually what happens and explains why you don't have any compression. If you can find a decent indy shop and the damage is limited to the head/valves you might be able to get it fixed for under 2K. This is an unfortunate weakness of that motor. Normally recommended replacement is usually at 100K miles.

I started thinking about most likely and common causes and I bet this is what happened. All rings on all pistons would not go bad like that.

Good luck, post your progress on this to help others.

[RickV]

I pulled the timing belt cover back enough so that I was able to see that it was still there over the top pulley before I bought the car so I know it didn't break. There is also a timing belt decal by the engine stating it was replaced at 96k miles. That's why I was curious if the belt slipped a tooth or 2 if the compression results I got would be possible? I just started ripping the front apart so I can access the belt and see if it jumped time. Maybe they changed the belt 20k miles ago but didn't replace the tensioner which then got weak and allowed the belt to jump. The front end has to come off to replace the engine anyway so I figured might as well. I'll keep you posted if I find anything interesting. Thanks for all the help.

[GIACuser]

Well good that you have eliminated the possibility of a broken belt. If the belt slipped it would put timing off but not affect a compression test.
If the belt was changed then it is very unlikely it is the issue assuming the work was done appropriately which I assume it must have been as the car has 20K miles on it since the work.
Hmmmm.... what will you find.

[RickV]

So the results are in. The camshaft seized. The crank pulley turns but it ripped off all the teeth off of the bottom of the timing belt since the cam pulley won't turn. I took the belt off and tried turning the cam pulley with a wrench but it won't turn either way. I also pulled the vacuum pump off the back of the cam to make sure it wasn't that, but it wasn't. I guess it wasn't getting enough oil and just locked up. So is it better to fix this engine or get a working used one?

[RickV]

Here's some pics

[RickV]

Maybe I should check the cam follower and see if that wore out. Could that have seized up the camshaft?

[GIACuser]

Maybe I should check the cam follower and see if that wore out. Could that have seized up the camshaft?

Well the fuel pump cam follower could be the point of failure. Unfortunately damage from this can be even more extensive in the more extreme situations. If the follower wore all the way through and the pump makes direct contact with the cam lobe you can get metal shavings into motor and they find their way to oil pump and block the flow. Engine is starved of oil and you get a seized motor. Trying to find all the metal pieces and clean the motor out can be done but it is risky because often you don't get them all. So you do the expensive rebuild, get the car running and a few days later or weeks your motor seizes up again.

if oil starvation occurs parts highest will seize first, ie camshaft. So it sort of fits

If this has happened - metal shards in engine - you will probably have to walk away from that motor and look for a replacement motor. Cost is about the same - rebuild vs putting a used motor in.

Note - the turbo can be rebuilt rather easily and economically, but you would have to do that also if metal has gotten into the oil.

[RickV]

I pulled the cam follower out and it's like new. No wear at all. What else could have caused the cam to lock up? Oil pump?

[GIACuser]

Oil starvation possibles
1. Not enough oil in car, didn't keep it full. (check dipstick)
2. Oil filter not maintained, plugged up.
3. Oil pickup screen plugged.
4. Oil pump failure.
5. Head gasket failure, oil going out of system into coolant lines.
6. Hit something in road, cracked pan, sudden loss of oil.

Drain oil and look for any glitter (metal)
Pull oil filter and look for any glitter
If you find metal you may just want to go for a used motor. If not you may want to consider saving the motor.

Since the cam froze it also froze the valves in a position while the crank kept rotating for a bit, likely the pistons came in contact with some of the valves and you have some bent valves which would explain the lack of compression as discussed earlier post.

So if no glitter might be worth repairing but you would need to pull the head to see how much damage there is. If it is limited to valves and cam that may not be too bad. you will of course need new timing belt kit, full kit the big belt, guides and the small chain stuff too.

If the head itself is not cracked (total loss if it is) the cam shaft that froze would need to be replaced and line bored (machine shop work but not real expensive).

May not have to pull the motor to fix it if it is just headwork.

[RickV]

Ok so I found a good used engine to replace my bad one. I'm going to order all those parts you suggested but I was wondering if there's certain seals and gaskets I should change too? I don't want to have to pull this engine to fix an oil leak or something right after I get it in. Thanks so much for all the help.

[GIACuser]

Well rear main seal, often the oil filter housing leaks and generally it is best to put a new housing on because the plastic does warp over time but at least put a new gasket in. Valve cover gasket. The vacuum pump up by the hpfp is often a point of oil leak, you can buy a new set of seals for it.

And of course while the motor is out have a look at all the vacuum tubing and replace as needed. There is one vacuum line on the transverse motors that is a hard line near the vacuum pump and it often gets brittle over time and you should just replace it. I suspect that your longitudinal motor would have that same line.

Not sure what your new motor is coming with such as injectors, turbo, coils, hpfp. If you have to take turbo from the old motor, it will have to come apart and you will need to at the very least flush it out. The middle section is one piece call CHRA, before you take the turbo apart see if there is any play both in/out and left/right of that turbo shaft. If so you will need to replace the CHRA. Fortunately they are not terribly expensive - around 200.

Also check the wastegate arm for play. This is the shaft from the outside arm to the actual wastegate flap. Ususally if this has play the turbo won't hold boost and usually you replace the turbo. A new K03 is about 600 dollars new. Probably can find one used for 1/2 that or less. There are kits on ebay to rebuild the wastegate setup but would only consider it if you have a friend that is pretty mechanical and can weld.

Good luck sir. Best to get a Bentley Manual (hard copy) for your car, will help a lot. Look for a used one on ebay, they are 149.00 new.

Also once car is up and running I use my win based laptop and Ross-Tech cable/software to do diagnostics and solve issues, super helpful tool. Ross-Tech.com

[RickV]

Thanks so much! I appreciate all the help. I got everything ordered and can't wait to get it back on the road. 🙏

[boomtime]

Ok so I found a good used engine to replace my bad one. I'm going to order all those parts you suggested but I was wondering if there's certain seals and gaskets I should change too? I don't want to have to pull this engine to fix an oil leak or something right after I get it in. Thanks so much for all the help.

Do as much as you can with the engine out. The tranny may also be easier to service, fluid and filter. Test compression on the used longblock before swapping it in, check for shavings in the swap engine oil pan, then install a magnetic oil drain plug with the new oil.

[GIACuser]

You are welcome. Let us know how things are going and how it all comes out.
In the short term I have a Bentley manual for the VW GTI same year as yours, many things are the same if you need pics of any pages of info just send me an email. I will pm you my email address.

[RickV]

Hey I've only got the turbo left to check out and my replacement engine will be ready to go in. I don't completely understand what to do to check its condition. I have it off the engine but what should I do next to see if it's good to use? Thanks in advance.

[GIACuser]

Hey I've only got the turbo left to check out and my replacement engine will be ready to go in. I don't completely understand what to do to check its condition. I have it off the engine but what should I do next to see if it's good to use? Thanks in advance.

There should be no shaft play. In/out or side/side.

Wastegate bushing that comes out of housing and connects to arm should have no play.

Look at blades, nothing broken.

Center shaft should spin freely and smooth.

[RickV]

So I pulled out the seized engine that has the cam locked up and found the chain tensioner failed. What kind of damage is likely done to the engine now? The head would need to be rebuilt but the bottom end is likely ok?