vazbmw
vazbmw HalfDork
2/26/20 6:54 p.m.

Folks,

Yesterday morning I went out to start my E39 525 and it didn't start...I had not driven it in a day, but it was running perfectly previously.

1. has fuel

2. has spark

but zero compression on all 6 cylinders.

I have never seen a car with zero compression...without a catastrophic failure. 
 

I poured some oil down the cylinders and got 150psi, but it goes back to zero once the oil is gone.

 

any thoughts or ideas?

 

thanks

 

Patientzero
Patientzero Reader
2/26/20 6:57 p.m.

Are you checking compression with the throttle open?

02Pilot
02Pilot SuperDork
2/26/20 7:38 p.m.

The rings are a problem and can break on the M54B25. It's a known issue. Now, breaking on all six at once? No, that seems unlikely.

My usual recommendation when it comes to any strange running problem on these is to look at the CCV. How that might cause zero compression I have no idea, but the low vacuum in the CCV caused all kinds of oil consumption past the rings in mine, so there's some relationship between the two.

AngryCorvair
AngryCorvair MegaDork
2/26/20 9:16 p.m.

Does that engine use the "valvetronic" system of varying intake valve lift?  If so, and if it failed in the "minimum intake lift" condition, you'd probably see really low compression on all cylinders, maybe low enough that it would appear zero.

vazbmw
vazbmw HalfDork
2/27/20 3:05 a.m.

In reply to Patientzero :

Yes to throttle opened

vazbmw
vazbmw HalfDork
2/27/20 3:09 a.m.
02Pilot said:

The rings are a problem and can break on the M54B25. It's a known issue. Now, breaking on all six at once? No, that seems unlikely.

My usual recommendation when it comes to any strange running problem on these is to look at the CCV. How that might cause zero compression I have no idea, but the low vacuum in the CCV caused all kinds of oil consumption past the rings in mine, so there's some relationship between the two.

I had no oil consumption.

just a normal car one day and a day or so later no start/no compression

vazbmw
vazbmw HalfDork
2/27/20 3:13 a.m.
AngryCorvair said:

Does that engine use the "valvetronic" system of varying intake valve lift?  If so, and if it failed in the "minimum intake lift" condition, you'd probably see really low compression on all cylinders, maybe low enough that it would appear zero.

It's not valvetronic. But, even so, I would not think adding a teaspoon of oil to the cylinders would seal up open valves (when I added a bit of oil, compression went to 150), right?

Shadeux
Shadeux HalfDork
2/27/20 5:31 a.m.

With Google-Fu this seems to be a fairly common issue with BMW's. I skimmed some threads and it seems the engine can flood and give you a no compression situation.  I doubt anything's broken, so that's the good news!

02Pilot
02Pilot SuperDork
2/27/20 5:51 a.m.
Shadeux said:

With Google-Fu this seems to be a fairly common issue with BMW's. I skimmed some threads and it seems the engine can flood and give you a no compression situation.  I doubt anything's broken, so that's the good news!

Flood with fuel? How does it get to zero compression - washing down the cylinder walls? What's the cause?

In certain conditions the CCV failing will dump oil in the cylinders, but that tends to be more catastrophic.

Streetwiseguy
Streetwiseguy MegaDork
2/27/20 6:25 a.m.

Lots of Nissan's lose all compression from flooding, too.  

Manual trans?  A tow start will be a whole lot easier on things than grinding the starter to death.

vazbmw
vazbmw HalfDork
2/27/20 8:18 a.m.
Shadeux said:

With Google-Fu this seems to be a fairly common issue with BMW's. I skimmed some threads and it seems the engine can flood and give you a no compression situation.  I doubt anything's broken, so that's the good news!

Thanks. I did. I saw things about rings stuck etc.

Came to the mountain of GRM to see if the oracles had any experience with this first or second hand.

vazbmw
vazbmw HalfDork
2/27/20 8:19 a.m.
Streetwiseguy said:

Lots of Nissan's lose all compression from flooding, too.  

Manual trans?  A tow start will be a whole lot easier on things than grinding the starter to death.

It's an auto

I agree

vazbmw
vazbmw HalfDork
2/27/20 8:20 a.m.

I bought some Seafoam, and I am going to make a mixture of that and trans fluid to see if I can get cylinders and rings to act right. Will update

 

 

vazbmw
vazbmw HalfDork
3/1/20 5:23 p.m.

Update:

I made a solution of Seafoam, transmission fluid and PB Blaster. I poured it in the combustion chamber and let it sit for a few days. I then poured a bit of motor oil in the cylinders and cranked it until it fired off. Created the biggiest smoke show that I have ever seen, but it's running, and running very smoothly. I now need to figure out what causes the cylinders to get washed down.

Thanks Everyone

-Vaz

Slippery
Slippery UltraDork
3/1/20 5:46 p.m.

Great news!

The solution is to never let it sit for more than a day laugh

02Pilot
02Pilot SuperDork
3/1/20 5:51 p.m.

Hit the redline at least once every time you get the engine up to temperature. I'm also a fan of the water induction steam clean - it does wonders at cleaning up the combustion chambers - but it's not for the faint of heart. And change the whole CCV system if you haven't already.

Slippery
Slippery UltraDork
3/1/20 5:53 p.m.

In reply to 02Pilot :

Whats that water induction steam clean you talk about? Might come in handy someday. 

Don49
Don49 Dork
3/1/20 6:25 p.m.

With the engine running at a high idle slowly spray water into the intake. It will decarbonize everything. Be prepared for lots of white smoke and keep the rpm's up as you do it.

Knurled.
Knurled. MegaDork
3/1/20 6:36 p.m.
Streetwiseguy said:

Lots of Nissan's lose all compression from flooding, too.  

Manual trans?  A tow start will be a whole lot easier on things than grinding the starter to death.

Nearly crapped my pants when this happened to the GA16i in my Sentra.  It sat for a couple weeks after I'd bought my Golf.  i went to move it and it cranked normally for about one revolution, maybe two, and then it free-spun like the timing chain had fallen off.

 

I clear-flood cranked it for about 30 seconds and it started to build compression again, and it was able to start.

 

I knew this could happen with rotaries, never experienced it with a piston engine before.  Apparently it was common enough with 1.8t engines that there was a TSB detailing how to get the compression back!

02Pilot
02Pilot SuperDork
3/1/20 7:33 p.m.
Slippery said:

In reply to 02Pilot :

Whats that water induction steam clean you talk about? Might come in handy someday. 

As Don49 said, it's basically introducing a small but steady stream of water into the intake (some prefer other solutions, like Windex for example, but water's always worked fine for me). Engine must be fully up to temperature, and do not let it stall. I put a small-diameter nozzle on the end of a hose and let engine vacuum suck the water in rather than forcing it. Just as a head gasket leaking coolant into a cylinder will steam-clean everything, so will this. I usually use a quart of water or so, depending on the state of the engine.

vazbmw
vazbmw HalfDork
3/4/20 10:15 a.m.
Slippery said:

Great news!

The solution is to never let it sit for more than a day laugh

LOL!!!

iceracer
iceracer UltimaDork
3/4/20 10:51 a.m.

A leak down test will show where the compression is going.

Why it happened suddenly could be a mystery.

vazbmw
vazbmw HalfDork
3/4/20 12:42 p.m.
iceracer said:

A leak down test will show where the compression is going.

Why it happened suddenly could be a mystery.

 

Compression was going pass the rings, since oil sealed up the cylinders. It seems to be a relatively common thing with these BMWs. The internets say there are two main reasons that it happens:

  1. Stuck rings
  2. Cylinders get washed down with fuel…maybe leaky injector

I didn’t know this until it happened, and I started researching.

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