BMW M5 Forum and M6 Forums banner

1 - 6 of 6 Posts

·
Registered
Joined
·
437 Posts
Discussion Starter · #1 · (Edited)
My M5 friends, I once again have a problem I have never read about and have spent 3 weekends chasing. I mean I literally have 40-50 hours chasing a coolant leak on what BMW calls a "voltage regulator for cooling system". I don't remember whether my M5 even had a transmission oil to coolant exchanger which they call "voltage regulator for cooling system", but my 2000 540i does and it leaks like a siv.

It started with what should have been a simple cooling system overhaul as I had a small leak at waterpump weep hole. When you remove the waterpump, you must also remove a tab that holds a steel line which runs just under the water pump and to the item pictured below which sits atop a large aluminum "tuna can" with cooling fins. When I replace waterpump and all hoses, expansion tank etc. I added coolant and it poured out of steel line that enters this VR for cooling system which just warms then cools trans fluid with engine coolant. I took the damn thing off and filled it with water holding my fingers over the ports and no leak which means I don't have a crack in the plastic. I have changed the O-ring twice which I had to order to no avail. I have done everything to make sure the steel tube is seated fully into the port and perpendicular on plane to the VR itself and it doesn't just drip...it has a steady dribble no matter how I move the steel pipe relative to the VR itself. BMW seems to have a crappy design here as it is simply a steel tube with an O-ring at the end which is basically just shoved into a port. All other lines have clips just like radiator hose to radiator connectors do at the nipples. This line is only kept from being able to back out of the regulator by the tab that is under one of the bolts that holds the waterpump in. The port that is leaking is on the far left in the picture below. You can see it is just a port with no means to secure the line that seats inside it. As crappy as it is, it obviously worked for 123K miles until I disturbed it. Now, no matter how I move the line relative to the regulator it won't stop leaking. I even checked 14.4mm X 3mm O-ring for size and I have the right ones.

Does ANYONE on this board ever recall messing with one of these things? I have had car down 3 weeks now spending both my entire Sat. and Sunday trying to resolve this. I am beyond exhausted and frustrated. I certainly never expected collateral damage on a waterpump job. Can anyone shed some light on this deal? I'm tempted to slather Silicon sealant all over the O-ring and shove it in, let silicon set up and hope! Please help me before I go postal...

Thank you ever so kindly and please don't delete because it is not on an M5. I have posted on your run-of-the-mill E39 boards to absolutely no avail. This board has never failed to get me in the right direction and I'd give just about anything I own to solve this very frustrating leak.

Bill
 

Attachments

·
Registered
Joined
·
1,782 Posts
Hi Bill,

Will try to help you out with this one. The M5 doesnt have a transmission cooler because it is a automatic transmission thing only, which is the reason why your 540 has one. It warms the fluid to get it to operating temp, then will cool it when it becomes to hot. As for that o-ring, its possible that when you are inserting it it may be tearing the o-ring when your installing it, spray some silicone spray on the o-ring before installing it to aid in the process of sliding it in. Inside the VR, where the pipe inserts, check for any signs of corrosion, if there is you may try a very fine sandpaper and *lightly* thin it out. If none of that helps, you can try maybe one size up o-ring.

Best of luck with your gremlin, you can PM me if you'd like and ill try to help out where i can!
 

·
Registered
Joined
·
437 Posts
Discussion Starter · #3 ·
I guess I could take some 1500 or 2000 grit sandpaper to the inside of the bore and then use the silicon or vaseline. I tried a ittle soap, but did not help. I thought the same thing about trying a slightly larger O-ring, but don't know who will sell just a few oddballs. What do you think about wrapping some teflon tape over O-ring? Thanks much for the help.
 

·
Registered
Joined
·
437 Posts
Discussion Starter · #4 ·
Guys,

I thank the many of you that have read and/or taken the time to consider my problem. I have posted for the third time on bimmerforum and not a single reply. The M5 forum was a long shot. My post doesn't belong here, but the mods here either remember me from my M5 days or they are just cool and are indulging my thread because they know the talent exists here somewhere to help. That is why this is the most professional BMW forum that exists and I suspect there is a correlation to be drawn between what you appreciate in your ride and your maturity level.

I tried patiently with a hard cotton wheel on my dremel; balancing getting an ultra smooth bore while not getting the wheel hot enough to melt the plastic. I used silicon spray and once again carefully seated the tube and a third new O-ring and you guessed it. I cleaned the tube as well, suspecting that it was really leaking from the inside of the O-ring where it should hug the steel. That did seem to slow the leak (combination of all of these tips), but the bottom line is that it is so precarious to hold the tube exactly right to slow/stop the leak that I could never trust it in real life driving. You would swear that I am missing something and that it is leakng near the port with the steel line, but I'm barking up the wrong tree, but if I manipulate the steel line enough, I feel I could stop the leak. Issue is the steel line is stronger than I am. I can not bend it and can see no way that it changed orientation with the VR. It simply can't move enough from where it must mount to have gotten bent or so forth.

So, despite my better judgment, I'm going to dry the heck out of everything and seal the line in place. Yes, I give up! The chance, assuming that I can stop the leak, of ever needing to remove that line is so minor, I'm willing to do whatever. The VR could be replaced as well as the steel line which is only about 18" long and connects into a rubber hose if it ever came to that. So, my question now is given that the cooling system generates 2 bar of pressure, but that the O-ring should handle 99% of the force, what is my best choice of material to seal it? I don't want anything that fully hardens. I want something with some give. My thoughts are silicon, hi-temp gasket maker, or something along these lines. Either could actually be removed if absolutely necessary, but they give just enough to tolerate vibration. Silicon is more tenacious than a lot of people really think and using it to fill what I perceive is a small void should be a piece of cake. I would put all around the O-ring, let it set-up fully and then pack the entire rest of the port to the end. I seriously doubt it would ever leak again in the cars normal lifetime. After all, we are just talking a MY2000 540ia!

Opinions? I am going to try one more thing first in that I tried teflon around the OD of the O-ring, but not around the steel tube which would affect the seal on the ID of the O-ring. I still just feel I am playing with fire since the whole deal did not seal right off the bat. The only thing that I wonder, but can't know is would the O-ring seal where I able to start the car and have pressure behind the O-ring? Just can't feel comfortable whatever. Anyone find an excellent sealer that is tough as nails, but stays somewhat plyable and would not crank like say marine epoxy?

Best & thanks all :byebye:

Bill Liedtke
 

·
Registered
Joined
·
6,642 Posts
Bill,speaking from experience with other setups that use a steel line in plastic,I had quite a few cases where the plastic part had some to the eye almost invisible hairline crack that made it leak.

I would suggest to replace the VR...
 

·
Registered
Joined
·
437 Posts
Discussion Starter · #6 · (Edited)
Excellent suggestion as on my last attempt to get it to seal properly today without using any sort of sealant, the port broke in half, suggesting that a hairline crack indeed existed. I have a new one on order. I will make sure when I install t that bolt that holds the steel line at the other end is out which will allow the line to move some and not put pressure on the port. Once it is in and seated, I will then install that bolt and I'm sure it will be fine. Thanks a lot to all that took the time to read and/or respond.

Bill
 
1 - 6 of 6 Posts
Top