PeachParts Mercedes-Benz Forum - View Single Post

Stevo · #7 11-09-2003, 11:56 AM

Diesel Power

Below is a copy of a .correspondence. the first is from me and the reply is from the guy that turned me on to this by pass flap thing. You might have the erosion problem he talks about.

Bruce

Well it sure would interesting to try a "NEW" and I mean new T stat housing. That would prove your theory. Actually that engine is now in a car I sold to a friend and it was well over a year ago I talked to you about this. It was running a little warm for no reason that I could find. It was flushed, good radiator, the works, MB coolant etc, etc.. The "80" engine I rebuilt (3K now) is running at 90C and will run a taste over that when on the highway.

Date: Sat, 08 Nov 2003 13:01:46 -0800
Steve,

I have two housings that are eroded and there is no absolute way to
determine their condition except by measuring the valve seat depth and
runout with a depth gauge. I have noticed that both of the bad housings
have dark discolored areas adjacent to the valve seat surface which might be
metal particles flushed from the wear surfaces. I suspect that the wear is
caused by two factors: electrolysis, and metal-to-metal abrasion between the
thermostat valve and the housing seat. The seat must be perfectly flat to
seal the bypass, and at the correct depth corresponding to the thermostat
travel. If not, hot coolant will leak past the bypass valve back into the
engine block instead of flowing through the radiator. The hole in the
thermostat valve makes the thermostat push the bypass valve farther into the
valve seat, hence sealing off the bypass better and forcing more coolant
through the radiator.

Bruce