Re: <E28> 88/535is heater

["Gilbert, Clark" <Clark_Gilbert@xxxxxxx>]

Gene - 

This is a classic sign that your heater core needs replacement. The worn
heater control valve gets stuck in the tapered body and can't overcome
the coolant pressure at highway speeds. When you slow down, the heater
core pops out and you get heat. Parts costs about $25, easy to do it
yourself. 

1. Valve body is located on the firewall on the driver's side. Clamp off
the hoses that go into the heater control valve block. I use vise-grips.
Little to no coolant loss.
2. Remove the top of the valve body. Three or four cap screws.
3. Pull out the guts. Note the order that all the washers and stuff fit.
4. Insert new heater valve core.
5. Reassemble. 
6. Unclamp hoses, very important for resumed heater functioning.

Clark
87 535is
Done that