Rattling noise in pump or thermostat...

[kapitaljin]

Hey guys, I was meaning to post this up a long while ago but forgot until I was doing some engine bay cleaning yesterday.

While the car is off, I usually check the hose pressure before unscrewing the radiator cap. However, when I squeeze and let go of the hose, I hear a subtle rattling noise, (like maybe baby rattle toy?) Its very subtle and sounds like its only a single piece rattling when I squeeze and let go.

I dont think this is normal but again, bimmers may be different???

BTW it is a 540i, 97, the water pump was not done yet but I do plan on doing it very soon.


Also, OT question, where is the brake master cylinder located and how do I get to it? I have a feeling its under the driver side filter housing. Please correct me if I am wrong.

[atlantisvip]

The impeller in your water pump could have broken and the pieces are flying around.. Not sure about the 5s but E36s had an issue with faulty plastic impellers.

[waterboy]

I had a 92 525i and mine would make that sound but not so much as what you said but mine was from the thermostat it has just a little play in it.Does the car get to hot or does the temp go up and down alot. My t-stat went out on that car and then knock out my waterpump so keep an I on the temp.

[kapitaljin]

My temperature doesnt fluctuate at all. However, about 3 weeks ago, my car kept dying on idle after I installed new plugs. After I took the car for a run on the highway, braught her back home and revved her up a little bit. It was enough to blow my radiator, luckily in the comforts of home, not the highway!

I beleive the sound was still present before the radiator blew up though. I replaced all the hoses, the expansion tank (although the tank and the sensor is still good) and ofcourse the radiator.

I am searching around for a well priced metal impeller water pump, and also the valve cover gasket as my plug valley's had some remains of oil. I was just wondering if I should replace the thermostat as well. I was just a little worried because of the subtle rattle, but it is hardly noticeable (when engine is off). I also found some idler pully play which may be what is causing this high pitch noice from the area as well but I dont know if the 2 idler pullys are the same...

Anyone know a good place for the water pump for a good price? I only know of pelican parts and its running at nearly 140 minus the gasket and o-ring.

[atlantisvip]

Definitely change the thermostat if you do the pump.

[bmwdirtracer]

The master cylinder is indeed under the driver's side microfilter box. Pull up the rubber moldings, remove filter lid and filter, squeeze hairpin clip that holds front of microfilter housing to inner fender, voila, no tools required.

Rattle, I'd have to hear, perhaps part of the water manifold system being normal, perhaps a piece of your rad, or water pump, stuck inside. Water pumps, and thermostats, on BMWs, are maintenance parts, and it's time, anyway. Can''t help you one where to find one cheap, beyond say realoem.com, etc. Do the thermostat while you're there, it's half the job without it, they live together.