If you get an intermittent and/or constant behavior, could be due some rust inside the Monovalve (solenoid exactly). Sandpaper (500 or thinner) the inside of the solenoid and the piston, could help to restore its normal work. Please do this with a cool engine.
It is a good idea to get the repair kit for the MV first. Due passage of time , o-rings and rubber parts inside could be fixed to the metal part, and get damaged/cracked when disassembling it, producing coolant spilling out.
The little spring could be broken too. I don't know if the repair kit includes one. If not, you can get one taken the damaged sample. I don't have yet the lengh of this spring but, completely compressed, it must be fit exactly inside the piston.
Being this solenoid a one way device, when it reaches a 12V signal, it blocks water flow (going downwards in this case). When the 12V signal stops, the spring pushes the piston upwards to allow hot water come inside the heatercore, sucked in the aux pump direction again. This may take place several times per minute to reach the asked temp inside the cabin.
Hope this will help you.
Last edited by Sprop; 10-18-2003 at 11:33 AM.