Low compression on #2 Cylinder

[trymes]

So, as anyone who has been keeping score at home knows, I bought a 505 turbo recently, as a bit of lark. Its a car in great condition, but has been a challenge mechanically since I got it, and it was available at a discount due to a few issues. Since I have had the car, I have had to work on replacing the turbo actuator, and it still isn't quite right. Perhaps that's due to the univrsal actuator I bought, perhaps it's related to the subject of this thread.

While working on the actuator and such, I noticed that the car is really leaking oil badly. It really became noticable when I forgot to tighten the clamps on the hose connecting the turbo's oil return line to the engine block. There was quite  a lot of oil on the undercarriage, plus lots of smoke when giving the car a bit of welly (I recognized the problem and addressed it quite quickly and topped up the oil - there wasn't that much lost, but it made quite a mess).

I noticed that the valve cover seemed to be leaking from both front corners, so I removed the cover and put Hylomar on the valve cover gasket, and it seemed to get a bit better, but I noticed that the LH side of the engine was dripping pretty badly today, after a short drive, so I did some cleaning of the block, pan, etc, and it looks like the leak is from the dipstick tube, where it enters the engine block. That led to my removing the oil filler cap with the engine running, which led to my noticing that there is a good bit of pressure in the crankcase, which led to an "Oh crap!" moment, which led to a compression test, which yielded these numbers (counting from 1 in the front to 4 in the back - is that the way Peugeot does it? No, it seems that Peugeot does it like the Jaguar XK, #1 is at the firewall):

1. 130
2. 80
3. 130
4. 130

These numbers led to a deep sigh and a fair amount of resignation. I don't know these cars that well, but here's my list of possible causes:

1. Broken Ring/Piston
2. Worn Cylinder Bore
3. Cracked Head
4. Bad Valve
5. Bad Valve Adjustment
6. ????

The only easy thing here is the adjustment, so I figure I should check it first and rule it out.

Does anyone have any thoughts, commiseration, or perhaps a known-good engine somewhere in the Northeast?

Tom

[trymes]

Joy. It looks like a bad bore and/or rings: I put some 20w50 in cylinder 2, and she pushed up to 140.

[Goce]

Tom did you do the compression test on hot engine with the throttle full open, putting oil is normal to increase the compression even on a new engine, as for the crank pressure you may have a block pvc valve or a dirty or wet air filter, if the engine idles well, don't really worry about it. I've driven na XU5 in a 405 for 3 years with 7 ,5,8,6 bar compression without any problems and the engine is still in use after i parted out the car.

[trymes]

Thanks, Goce. I originally tested the car hot with throttle open. The reading on #2 didn't change when I re-did it with the engine cold. I don't think that this car has a PCV valve, but I would love to be mistaken. This car only has a hose from the valve cover to the turbo inlet accordion tube, as far as I know.

I wouldn't be worried about the compression, as the car runs really well, and the plugs are all a nice clean biscuit color. However, the pressure in the crankcase is pushing oil out past the seals, which I cannot ignore (it's pretty bad).

[Goce]

I had the same problem with my father's 405 it turn out to be the air filter, it looks clean but it would blow out the tube from the valve cover and leak oil out of the valve cover gasket, looking closer to the filter it probably got wet at some point and cemented the fine dust, replaced the filter no problems any more.

[trymes]

Odd. I can't figure out how a blocked air filter could cause excessive crankcase pressure, but I don't doubt you. The PCV hose from the inlet to the valve cover is firmly attached, and the air filter is clean.

[Goce]

This is my first hand experience and my thinking is like this, engine when running is sucking air for the burning process with lot of force, but when the engine is at power stoke the engine pushes double the amount of air in the crankcase, that sucked in the combustion because pistons are in pair of two and only one fires at a time and if the filter is restricted even little it will make crank pressure, i only found out because i've accidentally left the clamp for the hose between engine and air box loose and it blow it out couple of time, changed the filter washed the engine and is bone dry ever sence.

[Bean]

Hi Tom,

I'd bring that cylinder to btdc and fill it with a 50/50 Acetone and ATF mix to make sure the rings are free - A stuck ring on  a car that's likely sat as much as that car has is not that unusual.  Another thing to try first would be see if you can find someone with a remote camera small enough to fit in the spark plug hole so that you can inspect the bore for scoring and the piston to make sure the ring lands are intact.

Stuck ring is the cheapest option, but worst case and you need a piston I can likely help you out as long as the piston is the same dimension.  Peugeot lettered pistons, so it would need to be replaced with the same letter assuming the bore was good.  IF it needs to be re-bored then you'd be better off with custom pistons in all 4, or a replacement block.

If I had to put money on it - I'd say stuck ring.  It would also be the explanation for having high blow by, but a word of warning - Overboost can be the cause of failed ring lands, but if that happens it usually makes a nasty racket as there are chunks of piston in the cylinder hammering everything inside.  (So I don't think it's that - but just a caution.)

Rabin

[Bean]

With respect to the oil leaking due to crankcase pressure  - the port on the valve cover that connects to the intake tube should be venting pressure building up inside the engine.  That port connects to the intake tube between the AFM and the turbo,.  That spot on the intake hose is vacuum when the motor is running., so it should draw PCV gasses into the motor to be burned in combustion. If the port on the VC or the hose that connects it to the intake hose is plugged you'll get pressure building up.

If memory serves there is a screen filter inside the valve cover - and that may need cleaning if air isn't "puffing" out that port.  Older engines also generate a fair amount of oil vapor in the PCV system - so I'm installing a Provent 200 inbetween the valve cover port and the intake tube on my car...  Eventually.

Rabin

[trymes]

Rabin: Thanks for that. Just as I am certain it's a broken piston and/or rings, you come along and offer hope - what a dangerous thing! I have now had suggestions of Acetone/ATF and Seafoam/STP Oil Stabilizer, and I bet I could find 1,000 other suggestions online if I looked. I'll try and do some homework, but I do have a few questions:

1. How best to tell when the piston is at TDC? I'm used to cars where the spark plug hole is much more accessible, so a chopstick or other method makes it easy to see where the cylinder is. The fact that this car is an automatic doesn't make it easier, either.
2. Do I need to crank the engine afterwards to shove the mixture out the plug hole/valves? Or does it just get burned up?
3. I tried a borescope (camera), but it just wasn't able to really give a good idea of what the cylinder and piston look like. I'm sure it was user error on my part, but the angle at which the plug seems to enter the chamber doesn't seem to be helping much, either.

Any thoughts you have would be great. There is definitely not any untoward noise coming from the engine, and I also realized why my oil leaks increased so much: I replaced the dipstick with no head on it with one that sealed quite well - the pressure (and with it oil) had to find another way out, and it did!

Tom

[trymes]

11 hours ago, Bean said:

With respect to the oil leaking due to crankcase pressure  - the port on the valve cover that connects to the intake tube should be venting pressure building up inside the engine.  That port connects to the intake tube between the AFM and the turbo,.  That spot on the intake hose is vacuum when the motor is running., so it should draw PCV gasses into the motor to be burned in combustion. If the port on the VC or the hose that connects it to the intake hose is plugged you'll get pressure building up.

Yeah, I have this hooked up to the intake as it should be, and there is no restriction. positive pressure makes it out of the elbow on the valve cover. It's almost certainly blowby.

Quote

If memory serves there is a screen filter inside the valve cover - and that may need cleaning if air isn't "puffing" out that port.  Older engines also generate a fair amount of oil vapor in the PCV system - so I'm installing a Provent 200 inbetween the valve cover port and the intake tube on my car...  Eventually.

Yes, I noticed oil in the hose leading to the turbo inlet, but this is pretty extreme pressure. Car drives just fine, though. Spark plug is a nice, toasty brown, just as it should be. I'll try to get something in the cylinder to see if a ring is stuck, but I don't think I am that lucky.

Tom

[Bean]

If you google 50/50 Acetone and ATF you'll find numerous sources verifying that it's one of the best rust penetrants.  Since it's relatively cheap, you'd have lots to fill the cylinder up with.  As for getting it out - if the leak is as bad as you say it likely will go straight into the oil pan, so you will want to do it with the oil drained and oil plug open so you can get an idea of how much is getting by the rings.  I'd do maybe 1/2 cup at a time if it leaks fast just so that it gets repeated doses of the stuff to see if it frees up the rings.  

If it doesn't drain fast - fill it up and let it sit as long as possible.  To empty you have to crank it with the plug out so that the piston expells the liquid out the plug hole.

BTDC is bottom top dead center = piston is at the bottom of the stroke.  Easiest way is to use a rubber hose on the plug hole, then crank motor over by hand and feel the air being sucked into and out of the hose.  When it's blowing out the hose and stops it should be at TDC.  Locate the crank mark and turn the crank 180 from there -  that cylinder should be at the bottom now.  (Air will suck in the hose as it goes down and then it will stop a the bottom of the stroke as well.)

Scope needs to have a light source, and it has to be fairly "bendy" to go into the plug hole and then fall to the bottom - hopefully you could see well enough to see if there was any damage.  I've never done it - Just thought it might be worth trying for peace of mind.

Make sure to check that PCV pipe off the valve cover - that should move a ton of air if it needs too and your motor shouldn't be pressurizing too much if it's working as it should.

Rabin

 

[Bean]

If it helps - I'm an eternal optimist, so I'll only settle for absolute proof before I'll concede defeat.   The stuck ring hypothesis is cheap and easy to pursue so it's worth it to me to give it a go at least.  

Worst case scenario is one you already accepted, so it can only get better for all intense and purpose.  If it is worst case scenario - Do you have the facilities and tools to pull the motor?  Even a single piston replacement to get the engine fully functional is a fair bit of work - but luckily your car is VERY nice and likely worth all the effort involved - but I might be a wee bit biased.  

Rabin

[Bean]

VVT sent me a picture of his intake that he just repaired and it occured to me immediately on your pcv problem - the connector on the intake tube has a tiny orifice - No way it will allow the motor to vent properly.

I'd look at either opening that metal part up to at least 1/2", or rigging up a filtered vent through a catch can set up.

Rabin

 

 

[trymes]

Well, to be more precise, I'd say that there is no way that restrictor will allow the PCV to bleed off all of the excessive pressure caused by blow-by that shouldn't be there to begin with!

On the other hand, enlarging the orifice in the restrictor will cause too much air to enter the intake without passing the MAF, no?

[Bean]

Technically - Blowby is already metered air.  

As much as it feels like, the actual volume of air will still be a small fraction of the air being consumed by the motor.

You could always plug the intake port on the hose and vent via a catch can to atmosphere instead until it's resolved.

Rabin