Where is the Coolant Going

[zonefive]

The #6 cylinder was very slowly leaking coolant through a worn head gasket. So, the top end of the engine is being rebuilt, along with new timing chains and guides.

Two of the spark plugs were contaminated with oil and the valves were leaking, so that is likely a significant component of the oil consumption (1 qt per 1,000 miles).

The piston rings are not going to be replaced. Not cost-effective. It will be interesting to see what the new oil consumption rate will be after the work is done because theoretically it will all be coming from worn rings.

[X5chemist]

How was the leak found? Do you have any pics?

[X5only]

Originally Posted by X5chemist

How was the leak found? Do you have any pics?

I bet via an endoscope peeking the cylinders with spark plugs removed or via Effduration's suggestion (https://xoutpost.com/1221915-post7.html)

[Effduration]

Piston rings are not likely worn… it’s far more likely that the bottom oil ring is clogged with carbon as the original oil drain holes were too small. Clogged rings can lead to oil consumption.

You can clean them with a proper BG Engine flush.

[X5chemist]

Originally Posted by Effduration

You can clean them with a proper BG Engine flush.

How's the BG engine flush used? I'm about to change the oil pan gasket. I can do a quick flush before draining it. After buying the X5, I did a Liquid Moly flush. The oil change was nasty black. Might as well do another good flush before the oil pan comes off.

[Effduration]

https://www.e46fanatics.com/threads/...ption.1259657/

See post# 4

It uses BG EPR #109 in the crankcase and among other steps, lets the car idle for several hours.

I have not done this myself, but would do it if I had a bothersome oil consumption issue.

MrMCar (author) is a long-time BMW Tech.

[zonefive]

I don't have pictures. I'm not mechanically inclined so I took the vehicle to a trusted mechanic and he did the borescope that was suggested here.

Of note, prior to the coolant loss becoming a major issue, I used Seafoam in the crank case prior to the last oil change to try and mitigate the oil consumption. Consumption went from a quart every ~700 miles to a quart every 1,000 miles. And the engine ran with less vibration at idle as well.

Not sure how Seafoam compares to the BG product.

[EODguy]

For me...

I've found/had small leaks from the o-rings on the transmission cooler, the smaller diameter hose from expansion tank to water pump, leaking drain petcock on radiator tank and a hairline crack in the radiator plastic tank that masu have seeped only occasionally until it detonated the other day.

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[jdstrickland]

Originally Posted by zonefive

I'm losing coolant at the rate of about 2 oz per 100 miles for about the last 2,500 miles. I've taken it to two BMW indies.

The first could find no leak and said he was stumped. Pressure tested the car overnight. The second said he found a radiator and a thermostat leak via pressure test and he replaced both.

After the radiator and thermostat were replaced, the low coolant light came back on after 400 miles. The indy who replaced the radiator/thermostat told me there were no external leaks after a second pressure test but that they car smoked on start up after the pressure test and told me I need a new motor because the engine is consuming coolant somehow. Compression of all cylinders was over 200 except for #1 at 175.

I've owned the car since new. 2001 3.0 207,000 miles. The car has never overheated. The engine has no power issues, never smokes on regular start up, idles smoothly.

The second mechanic told me that it cannot be the expansion tank, which was replaced 35,000 miles ago, because it did not leak under pressure. The water pump was replaced 65,000 miles ago. They said they checked the coolant pipes going in to the engine and they had no leaks.

The first mechanic told me to keep driving the car until the source of the coolant loss revealed itself, and he doubted there was a crack in the head or block, or a head gasket failure because there would be other symptoms besides a slow coolant loss.

It's tough because I feel nervous driving the car for extended distances -- don't want to get stranded by the problem ultimately getting suddenly much worse.

Tempted to replace the rest of the cooling system --- hoses, expansion tank, and water pump and see if it stops the problem.

Advice appreciated.

I JUMPED IN WITHOUT READING ALL OF THE POSTS....

I had an E36 with the M50 engine, and I missed the part where you say which motor you have, so my comments might not help you in your quest for information.

My M50 developed a cracked head that gave me absolutely in symptoms at all, except for the minor (like yours) consumption of coolant that could not be explained. You should Google, BMW M50 CRACKED HEAD, then look at the Images. I'm pretty sure the M54 will have a similar, if not identical, problem.

The Backstory....
I had just bought my E36 and was driving it over a mountain road to commute to the office. I was coming home one night and smelled coolant, not realizing it was mine I passed a couple of places where I could pull over and wait for the tow truck, except that cell service on this road was spotty at best 20 years ago. By the time I realized that the coolant was mine, I stopped and hosed down the front of my car and attempted a roadside repair that held to the summit of the road I was on, then I coasted without the engine to the bottom of the hill and called AAA. They brought the car to my house, I bought a bunch of stuff and put it on, and this cured the immediate problem, and brings us to why this is relevant to you. After I fixed the catastrophe, I found that I was consuming coolant similarly to your consumption. Then, one random Monday morning several months later, my engine hydrolocked upon Engine Start in my garage. I pulled the plugs and turned the engine by hand and the contents of Cylinder 3 came out. Coolant.

My car was consuming coolant very slowly, and there was a crack between the #3 Exhaust Valve Seat and the adjacent water galley. The coolant was leaving so slowly, there was no perceptible steam. Temp control (by the needle remaining at midscale) was good. My mechanic could not explain the hydrolock, except to say that the head gasket was toast. When he pulled the head, he discovered that the head gasket was not toast, and we needed to find a different problem. That's when I found out about BMW Cracked Heads.