Mysterious M44 Coolant Leak - Please Help!
 

Hi all,

I've noticed a puddle of coolant under the AC compressor on my 1998 318ti (203k miles) in the last few weeks. I bought the car last May, and had no cooling issues until this - perhaps not coincidently we had our first cold front move through around the time the leak started (overnight lows in the mid-teens).

I've tightened the hoses on the T-stat and have cleaned the front of the upper timing case to check if this is where the leak is coming from. I don't see any evidence that the leak is from the T-stat housing or the hoses.

The leak appears to be coming from near the mating surface of the upper and lower timing case covers just below the timing chain tensioner. There is visible coolant coming down both sides of the compressor. Does the m44 have a profile gasket that could leak coolant in this area? Any other thoughts as to what may be happening?

I've driven the car about 70 miles since this has happened and have not noticed any white smoke or mixing of oil and coolant.

Any thoughts appreciated. Thanks!

Yes, there's a rubber profile gasket that sits between the top of the timing chain case and the bottom of the cylinder head, it's #10: http://www.realoem.com/bmw/enUS/show...diagId=11_6003

If that's where the trouble lies, I'll pray for your soul, as that's a bitch to change. I ended up removing the head to get the new gasket in. But, I think there's a way to replace it without removing the head.

It sounds like you've ruled out the water pump, as you're seeing coolant above it?

By the way, where are you at? I'm in Greeley.

Paul
'96ti 246,800 mi.

Hi Paul,

Thanks for the response! Yes, it does seem to be coming down from near the top of the AC compressor which is above the water pump, so unfortunately I don't think that is where the leak is. I haven't been able to catch drips of coolant anywhere above the bottom of the compressor.

When your profile gasket failed, were you seeing coolant leaking on the outside of the block, or were you having symptoms of coolant mixing with oil? I would have thought that the profile gasket would allow coolant into the timing case, but maybe not always?

I used to live in Windsor, back when I had the 95' 318ti. My wife worked at UNC in Greeley, so we know that area well. We are in Albuquerque now. I'll update my profile now.

No coolant - I changed the profile gasket due to oil leaking out of the chain case, where the case and cover meet. The oil was dripping down the right hand side, near the tensioner. I haven't noticed any co-mingling of oil and coolant.

The issue, when replacing the gasket, is that the new gasket has not been compressed, thus takes a lot of force to slide the chain case back in. And the rectangular coolant passage on the underside of the head will tear up the gasket when you try to slide the chain case into position. The solution is to use very thin feeler gauges, either 0.001" or 0.002" thick, well lubricated, during the install. Then pull them out afterwards. I can tell you that I used 0.006" thick shim stock and it was much too thick, couldn't pull it out without distorting the gasket.

The '95ti - did you buy that 2nd hand? I worked with someone at HP in Loveland, they had a green 'ti, think his name was maybe Edgar or Edwin, wondering if it was his originally.

Hi Paul,

Sorry, I just saw this. You're right, I think this is the dreaded profile gasket. As the leak only shows up in winter and I mainly only use this car around Albuquerque, I've decided to just live with it.

The Green m42 ti, I bought in Denver in 2014. I bought from a younger guy in his early 20s at the time. I sold the car in 2017 to a guy in Oklahoma to make room for a manual E46 Wagon.

I missed the ti so much, I replaced in in May, 2018 with a Titanium Silver, 1998 318ti Msport. I'm slowing going through it. After doing a 250 mile trip in it yesterday with no AC when it was 106 degrees out on the return, I'm not trying to troubleshoot that.

Do you know much about how these systems function on the ti? I diagnosed the clutch on the compressor as not engaging due to too low of refrigerant. Refilled to 35 psi on the low pressure side and now the clutch engages correctly, but I still have hot air at the vents :confused::confused::confused:

AC is not my strong point - while 35 psi may be enough to make the compressor clutch engage, I'm not sure if it's enough to get cold air. I'd try charging it a bit more just to rule out low refrigerant. The other thing to look at is the hot/cold control - I think it controls a mechanical damper. The cable assembly has been known to fail - you'll feel a lack of tension when you rotate the knob, if it's broken.

Hey Paul,

Boom! - You hit the nail on the head. Turns out my old low-side gauge was not reading pressure correctly and it only was at 20 PSI. Used a new gauge, filled to 32 psi (that's about all it would go) and now I have cold air. Clearly there is a leak and we'll see how long this holds pressure for.

Good call on the damper - I wasn't getting heat a few winters ago and ended up zip tying my Boden cable to the center console to get the appropriate tension to move the damper. It's not perfect - but is unseen in the cabin.

How is life in Greeley? My wife used to work at UNC and I hear things are very difficult there amidst the pandemic. I hope the rest of Greeley is doing well. I really liked that town - much more friendly and less pretentious (I thought) than the front-range towns.

Thanks again!

Rob

I've had varying success chasing AC leaks - on one vehicle, it was subtle, never did find it. On another it was blatant, refrigerant bubbling out due to old dried up orings.

I'm very careful when I move my temp control, because it's such a common failure. It can be a little sticky, but I gently coax it.

The epicenter of the virus here is the meatpacking plants - close quarters and minimal masks, I suppose. I've been here since 1989, moved from back east (NJ) - pretentiousness; that's one thing you don't have to worry about here in Greeley. I was in ABQ a few years ago, had a meal at Twisters, aka El Pollo Loco, sat in Walt's booth. What did your wife do at UNC?

She worked as an academic advisor with the performing and visual arts students. She also got her M.A. in academic advising at UNC.


Let me know next time you're in ABQ!