Milky oil. Thoughts?

[greeny525]

1993 E34 525i

https://uploads.tapatalk-cdn.com/20240517/8c5e0ecafcf79125478396b294d65c04.jpg

I did a head gasket job a few months back but I haven't brought the car out for a drive yet because I still have other things to do on the car. I thought it would be a good idea to warm the car up periodically just to keep the engine running and every time I do so, I check the coolant level and it hasn't dropped until now.

I just now realized when I checked under my fill cap and dipstick, the fluid appeared milky. And so I thought I should change the oil and as you can see from the photo, it looks concerning. Fyi, this oil is from my 3rd oil change after the head gasket work.

After reading a few threads, I learnt that it could be condensation but, could it be this excessive??

[fo3]

Sorry mate, but that is screwed. No way oil looks like that unless complete head gasket failure.

[whiskychaser]

A bit of mayo under the filler cap could be put down to short journeys during cold weather. Unfortunately, this looks much more serious. What was the reason you were obliged to replace the head gasket once already? Next steps: pressurise the cooling system and check for leaks, check for water in the cylinders and then compressions? And perform a sniffer test? BTW, did you disturb the timing chain case at all?

[greeny525]

A bit of mayo under the filler cap could be put down to short journeys during cold weather. Unfortunately, this looks much more serious. What was the reason you were obliged to replace the head gasket once already? Next steps: pressurise the cooling system and check for leaks, check for water in the cylinders and then compressions? And perform a sniffer test? BTW, did you disturb the timing chain case at all?

I bought the car as is as my first project car. Previous owner sold it with a failed head gasket or so he claimed.

I will do those tests once I have the test kits. I remember the machine shop saying my cylinder head was good. I did not disturb the block though, because it wasn't something I wanted to touch on yet. Could it be a crack between the coolant and oil jackets in the block? Is it common on M50s? And yes, I did remove the timing chain case to replace the broken plastic tensioner guide. Installed everything back with new gaskets and torqued to spec.

[whiskychaser]

Yes, you can't tell by just inspecting it if there is a crack in the head. So before you refit it, it is best to have your shop pressure test and skim it. Did you replace the locating dowels when you refitted the timing chain cover? It carries coolant and if you don't get the height correct and sealing surfaces water tight, coolant can leak out between the cover and the head or down into the sump. The original timing chain cover gaskets are paper thin and it is quite easy to disturb them when refitting the cover.

[greeny525]

Yes, you can't tell by just inspecting it if there is a crack in the head. So before you refit it, it is best to have your shop pressure test and skim it. Did you replace the locating dowels when you refitted the timing chain cover? It carries coolant and if you don't get the height correct and sealing surfaces water tight, coolant can leak out between the cover and the head or down into the sump. The original timing chain cover gaskets are paper thin and it is quite easy to disturb them when refitting the cover.

I'm not sure what sort of tests they did on the head but they did skim it. It was a reputable machine shop, so I trusted their work.

No, I did not replace the locating dowels. I did use RTV with the paper gaskets when refitting the cover though. I guess for now I'll just have to do the tests you mentioned before and report back.

[danespann]

I'd not condemn it until you actually go drive the thing. If it has good compression numbers and isn't disappearing coolant it's probably fine. If you live in a humid place, the oil will pick up a good bit of condensation when just idling it with no load or with owners who exclusively take very short trips.

[greeny525]

I'd not condemn it until you actually go drive the thing. If it has good compression numbers and isn't disappearing coolant it's probably fine. If you live in a humid place, the oil will pick up a good bit of condensation when just idling it with no load or with owners who exclusively take very short trips.

What range of pressure should I be looking at for compression?

I would say I live in a humid place but could condensation be this excessive? I do notice a slight oil leak from the oil filler cap, could this be a reason for moisture to get in?

[whiskychaser]

Bentleys says minimum compression is 142-156psi with a max difference between cylinders of 7 psi.

You can have great compressions and still lose coolant. If water is getting into the cylinders, the engine could be damaged when you try to start it as water will not compress. Remove the plugs and check if any of them are very clean. With the plugs out, you could turn the engine over briefly. If the head gasket has gone, you can sometimes get a fountain coming out of a cylinder.

[greeny525]

Bentleys says minimum compression is 142-156psi with a max difference between cylinders of 7 psi.

You can have great compressions and still lose coolant. If water is getting into the cylinders, the engine could be damaged when you try to start it as water will not compress. Remove the plugs and check if any of them are very clean. With the plugs out, you could turn the engine over briefly. If the head gasket has gone, you can sometimes get a fountain coming out of a cylinder.

If water were to enter the cambers, I should expect to see smoke coming out of the exhaust when the engine is running right? But there were none. Even so, I'll check the plugs as soon as I can.

[greeny525]

Just pressure tested the cooling system as per post #2 here - https://www.bimmerforums.com/forum/showthread.php?1828511-How-do-i-do-a-coolant-pressure-test


1st test

Hooked up the tester and pumped 15psi into the expansion tank and inspected for leaks.

Results: Losing pressure. Found minor leaks from the hose connections at the front and rear of the engine. Tightened the hose clamps and repeated the test. No more external leaks, moving on to the next test.

2nd test
Pressurize the system to 20psi and monitor any pressure loss after 2 hours.

Results: Pressure dropped to about 12psi after an hour into the test with no external leaks.

Welp! As you guys have suspected, this definitely means I have a head gasket failure. Very unfortunate, but you live and you learn. I'll send the car to an authorized mechanic to run the other tests and have the car fixed up when I am financially able to.

[whiskychaser]

Sad news but not totally unexpected. As you say, next step is to find out how/where coolant is getting into the oil.

BTW. You mentioned changing the tensioner arm but did you consider changing the guide(s)?

[greeny525]

I just ordered a compression test kit so I'll run the test once I have it.

And yes, I've replaced most of the timing components - Timing chain, Tensioner arm/guide rails and Tensioner spring

[greeny525]

I inspected the spark plugs as you suggested, whisky, and here's how they look:

https://uploads.tapatalk-cdn.com/20240521/c5a26d63d1dffa0d206f9a755fd981e5.jpg

None of them appear very clean so I would assume there weren't any coolant entering the cylinders. I do notice some greenish residue around the insulator though. Not sure if that's coolant since I have the BMW blue coolant in the system.

Also, I checked the piston tops through the plug holes by simply shining a light into it and they don't appear abnormal. Just carbon residue from combustion.

Now, while the plugs were out, I tested the compression and here are the results:

Cyl 1 - 160psi
Cyl 2 - 160psi
Cyl 3 - 157psi
Cyl 4 - 150psi
Cyl 5 - 153psi
Cyl 6 - 134psi

It appears Cyl 6 isn't getting enough compression. Would this narrow down the area where the head gasket failure is located?

[dannyzabolotny]

That's a little low compared to the rest, but the neighboring cylinder is fine... usually a typical head gasket failure (in the combustion area) will show up as two adjacent cylinders being equally low (typically 5 & 6). That being said, you may have a head gasket failure or crack in the head in the coolant/oil passage areas that's not affecting the combustion seal, I've seen that plenty of times too.

[whiskychaser]

Is the green deposit greasy or like a powder? If it is greasy, it may just be some form of dialectric. The centre electrodes look wet but that may be just my screen.

Low pressure on 6 could be the HG, a crack, or a problem with the rings/bore. You can narrow it down a bit by adding a teaspoon of oil before testing each cylinder and repeating the compression test.