Running Warm Again

[FoMoCoGoGo]

1987 325E, 5 Speed.

Within two weeks i replaced the radiator, with another used one from a friends car. He used it for months and his car ran under the half mark. New thermostat, water pump, timing belt, Upgraded the E fan clutch to I, and replaced the head gasket. STILL, it runs on the third notch. One of the thermostat sensors looks messed up, all broken to hell and has a loose connection? Could any of these sensors cause it to run warm? Before you ask the cooling system is currently just running water. No leaks, has pressure, i bled it properly, many times.

Any ideas would greatly, greatly help, This is getting very old.

Anyone?

[chefthomas]

unless you have your core pressure tested my guess would be the radiator, when it is running hot feel around for cool spots and I feel your pain as I am going through the same right now. Best of luck

[dashboardmonkey]

bleed it lots with the heater running full blast

and when you think you are done bleeding it, do it some more, prefferably on an incline withe front up higher of course

[Dunnavant]

As I discovered a few months back there is a poor design thermostat out there that doesn't allow proper flow for these engines AND doesn't allow proper bleeding unless you drill a good size hole in the plate before mounting. Can't recall the brand but it is not one that our favorite sources carry (I bought two before I learned).

I think I bought a proper one from BavAuto, which is working fine today. Before mounting it I did the following:

- Placed the proper style and the poor design in a pot of water and heated.
- At the same temp. both began to "open"
- At the same lower temp. both began to close

It is very obvious, with them side by side, that the proper type will allow flow sooner and much more flow fully open than the poor design. The poor design also would begin to restrict flow much sooner as it closed. Not as obvious just looking at one right out of the box.

I would mention a brand but can't find my notes yet. They are common and probably make good products, just not this particular one for this purpose.

Found my notes. CST # 3087 and similar are the GOOD and PROPER design.

DO NOT, REPEAT, DO NOT install an AEOLUS THOMSON or similar thermostat in your M20 as this can cause you much grief even if it is just a wasted day or three of bleeding air from the system. This style thermostat is basically a bubble generator and even when fully open will restirct flow as if you had your thumb over a garden hose (compared to the correct style).

[FoMoCoGoGo]

Thank you, i will drill a hole in my thermostat and see how that goes.