Is my 3.0 toast?
 

So, 2004 X5 with 3.0 and 280,000km on the clock.

Recent problems with the cooling system including exploding expansion tank which also tore the neck off the radiator. Cooling system issues may or may not be related to a failed electric pusher fan, but not sure.

Extended diagnostic cycle has included a cold compresion test (obviously can't do it warm with the cooling system in pieces):

1: 165
2: 160
3: 160
4: 105 (yes, one hundred and five :()
5: 165
6: 175

Cylinders other than 4 came up to about 120 on the first stroke, then a 10 or so per additional stroke until maximum reading - about 8 strokes - pretty normal, right? Cylinder 4 came up to 40 on the first stroke (ugh) then up by 10 per stroke to 105. Repeated back-to-back tests on 4 showed higher and higher maximum readings, likely as the oil was pumping up around the rings: 120/130/140/150 with about 8-9 strokes each time. I didn't try with added oil

Spark plug 4 came out wet. Can't tell if it's oil or coolant.

So I thought maybe I was dealing with a blown head gasket but that wouldn't give better compression readings on subsequent tries. At least I don't think so.

Today I borrowed a cylinder leakdown tester and now I'm really depressed. I did tests at 80psi in since that's where my compressor trips to recharge:

1: 80/77 - no leaks heard

2: 80/68 - air leakage at oil cap

3: 80/40 - air leakage at oil cap and in cylinder 4

4: 80/45 - slight air leakage at oil cap and large leakage at cylinder 6

5: 80/37 - slight air leakage at cylinder 4

6: 80/77 - no leaks heard

At no point could I hear any air coming out the cooling system at thermostat housing.

Any ideas what I'm dealing with here? I'm thinking wherever I hear air from other cylinders it may be leaking intake valves. At no point did I hear air out the exhaust.

I'm thinking of getting a cheap used radiator and putting it back together and selling it...

Sorry to hear about the problems. Sounds a little similar to my situation now:

https://xoutpost.com/bmw-sav-forums/...s-coolant.html

I'm at about the same mileage. My compression numbers were way higher (180-200 psi), so I'm currently tearing it down to replace the head gasket and anything else, unless it is beyond reasonable repair.

In my case, the expansion tank had been replaced about 30k miles ago, so it did not explode, rather it blew out a small enough hole in the upper radiator hose to release the pressure. After replacing both radiator hoses and a new radiator (old one was fine) pressure would build up in the cooling system (I believe from combustion gases, rather than overheating) and the pretty new radiator cap would release coolant at 2.0 bar.

I did a reverse pressure test that confirmed coolant getting into cylinders 2+3, but given the high compression, I'm optimistic enough to try to repair it.

A test for combustion gases in the coolant will be helpful in diagnosing, and is very easy to do. EDIT - ... if your cooling system is intact.

Regarding your thought to slap a replacement cooling system on there to dump it, you may find yourself in the same situation I was in - if the problem involves a leak from the cylinders to the cooling system, you'll get pressure and it will need to go somewhere, and there is no external fix to that one.

Anyway, hopefully my similar experience and tests might help in your case.

My comprehension test was done cold - was yours? Car ran strong before this.

I need to get it running again in order to do more about possible leaks to the cooling system.

yes, my compression test was done cold. I'll do a leakdown test soon, which will be cold too, since the intake and exhaust manifolds are off.

Sounds like a blown head gasket in cylinder 4.

Thinking about your generally low compression numbers ...
(sorry if these are not helpful, just trying to think of a happier explanation than that your engine is worn out beyond some big problem with #4)

Was the throttle wide open?

Was a battery charger hooked up to the jump ports in the engine bay during testing?

DME relay removed?

Does your compression gauge have a Schrader valve right at the end that screws into the spark plug hole, or is it somewhere else along the hose?

I don't need to do compression tests very often on my cars, but that issue you had of the numbers increasing on subsequent tests seems weird. Maybe a problem with your test setup?

This is DBW throttle, so testing was however the throttle sits when cranking with the DME relay removed (IOW, I don't know). Comp tester has a valve on the gauge body next to a quick-connect in addition to one at the tip of the hose. The gauge will hold pressure reading with the hose popped off the gauge. Battery is new and was fully charged. Cranking speed was good and high during testing and did not taper off.


As for the head gasket, I'm leaning toward that being the case, but with three cylinders leaking into the crank case I'm leery of the integrity of the bottom end - hence the "is my 3.0 toast" thread title.


At the moment, I'm shopping for a used lump to see what I'm in for that way.

A used lump for C$1500 sounds like an attractive deal, assuming I can verify its compression and leakdown number.

Found a lump with 183,000km for $800 exchange. Looking more attractive all the time.


BTW, if you're doing a compression test with all plugs removed (SOP), opening the throttle probably makes little difference as the other open plug holes will allow lots of air in. YMMV.

I'm not sure I'd go for another block, especially with unknown history. How much to reman yours? Surely can't be more than $800 in parts? Sounds like an interesting task as well - while you're at it you could do all the known gaskets that have issues on this car and have an engine that will easily last another 200-300 km, and you KNOW it's been done right.