525 thermostat

[yaofeng]

I never paid attention to the 80 deg C thermostat when I installed in May along with the aluminum thermostat housing the the SS impeller water pump. It has been giving me coolant message recently. I forgot I did the thermostat and bought one 88 deg C. Today I took it out because it was leaking, actually the car was overheating. The water pump o-ring was intact. So was the irregularly shaped red rubber ring. But the thermostat o-ring was very deformed, also with some crust. I also found the thermostat doesn't have a bleed hole. Those on my SAAB's all have one. While I don't believe in tampering with original equipment, what is the Board's recommendation on the bleed hole?


http://i21.photobucket.com/albums/b274/yaofengchen/BMW_95_525i/DSC_3258.jpg

[R1daveg]

Was it a genuine BMW item? IMO it is a good idea, sticky thermostats are well known problem. Makes sense to have a pressure relief instead of blowing your rad apart. I dont think the bypass flow (with a small hole of course) would be sufficient to interfere with the function of the cooling system. It may not be ideal in very cold climate though..

[neil_004]

i've seen the bleed hole recomended and did it on my car. works great just keep it small and put it as high as possible on the thermostat.

[granit_silber]

Drill the hole through the arrow or marking that signifies "this end up" on the t-stat. Make the hole small, I can't remember the exact size, but the bit I used was one of the three smallest one in the set (1/16 or 1/32?). After the hole is drilled clean up any shavings on the stat and insert with the hole at 12 o'clock.


-ashley

[Bill R.]

people here drill them.




I never paid attention to the 80 deg C thermostat when I installed in May along with the aluminum thermostat housing the the SS impeller water pump. It has been giving me coolant message recently. I forgot I did the thermostat and bought one 88 deg C. Today I took it out because it was leaking, actually the car was overheating. The water pump o-ring was intact. So was the irregularly shaped red rubber ring. But the thermostat o-ring was very deformed, also with some crust. I also found the thermostat doesn't have a bleed hole. Those on my SAAB's all have one. While I don't believe in tampering with original equipment, what is the Board's recommendation on the bleed hole?


http://i21.photobucket.com/albums/b274/yaofengchen/BMW_95_525i/DSC_3258.jpg

[Alexlind123]

What is the purpose of a hole??

[Mendozart]

Some people say it helps in the bleeding process, but you don't need to do this on an m50 engine. I think it mostly helps on m20 & m30 engines.

[yaofeng]

I must have messed up somewhere. As soon as I pour coolant into the tank, the leak starts at the thermostat/water pump area. Let me get this straight first. The thermostat goes into the block first pointed side facing out. The o-ring goes in next and then the thermostat housing. Correct?

Have to take everything apart again. My driveway is all wet.

[Alexlind123]

Some people say it helps in the bleeding process, but you don't need to do this on an m50 engine. I think it mostly helps on m20 & m30 engines.

I just poured in my coolant, squeezed the upper rad hose a bit, and started the engine. Once it was heated up, i opened the bleed screw. Since no air came out, i closed it and it has been perfect ever since.

[yaofeng]

For a while I thought I had a cracked head on the 525. After reinstalling the thermostat and water pump and filled coolant it started dripping. So I removed the AC compressor, the AC bracket, the two s-belt, all pulleys and the flex damper to have a look. Turned out the coolant was leaking from the bottom of the water pump to its mating surface. This is the SS impeller WP I put in three months ago. The WP o-ring is still very elastic. I am puzzled. Hope I don't need anther pump again.