Help!!! coolant leak after switching to 0-40 synthetic !!!

[e34musician]

Conincident? Or head gasket:(

I decided to covert from high mileage oil to Mobile 1 0W-40 yesterday. The car now have obvious coolant leak (repeat, coolant leak, not oil leak).

Has anyone seen this before? Are they related? I am going to try to find the source of leak today. Please help !!!

Thanks!

[Blitzkrieg Bob]

cooling system is just jealous

[632 Regal]

theres all kinds of hidden places a leak could come from. If its the rear you have a bunch of hoses and the aux water pump, front has pissers and stuff so check around carefully.

[e34musician]

cooling system is just jealous

That's good one :) Thank you and Jeff.

Found the leak. It was the hose that connects lower right of radiator to the water pump (themostat housing). It leaks at the waterpump and drips down into the oil pan. Will have to remove the airduct and probably MAF sensor to change this hose and clamps. And of course drain the raditor.

Where do you guys buy radiator hoses and clamp? Does it have to be OEM? I tighten the existing hose clamp. Hopefully, I can wait a couple days for parts.

There are actually also some slow oil leak from the driver side (upper left (front) of engine). I need to figure out if it's engine oil or PS fuild (or both:( ) - I had to top off the expensive PS fuild from time to time, but never notice any oil consumption.

[632 Regal]

I replaced all hoses and thermostat and housing so I dint have to worry about it for at lease 10 years. Choice is yours what you want to replace, my car is good for another 9 years without worries, no cooling probs expected for 9 years, then i'll do it again.

[Tiger]

T-stat housing... very common... change it to metal one... change everything while you are at it.

[e34musician]

T-stat housing... very common... change it to metal one... change everything while you are at it.

I notice that I still have the plastic T-stat housing. I will get the aluminium one (MTC) on line. Will also get a new T-Stat.

2 questions.

1.) Found 85C Wahler/Behr T-Stat at Autohausaz. $28 bucks. Any good? Is 85c too low?

2.) Do I have to worry about bleeding the system after refilling the coolant? I heard M60 has a self-bleeding system. Do I have to drill a hole on T-Stat for bleeding?

[Tiger]

1.Normal... yes good brand... 85C not 85F if you are thinking too low.

2. It is self bleeding.

Yes, from what you said where the leak is... it is the thermostat housing that is cracked and leakign from the seams of the plastic housing.

[e34musician]

1.Normal... yes good brand... 85C not 85F if you are thinking too low.

2. It is self bleeding.

Yes, from what you said where the leak is... it is the thermostat housing that is cracked and leakign from the seams of the plastic housing.

I changed lower hose, clamps, T-stat, T-stat housing and aux fan temp switch last night. No more leak! Thanks for all the info. I was able to change the housing w/o removing the water pump (U joint socket did the trick). I boiled the new T-stat to make sure it works before removing the old one.

I noticed that the old T-stat has BMW stamp on it and the temp is 95c. My new T-stat is 85c. Is that OK for M60? I noticed that my temp gauge is now slightly lower than 12 o'clock when fully warmed up. It used to be slightly higher than 12 o'clock. 10c cooler, Is this a good thing?