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MG MGB Technical - Failsafe Thermostat

Not sure if many people have been using the "Failsafe" thermostat from Moss, but I put one in two years ago and it all ready went bad. I had noticed that my 73B started running cold so I pulled the thermostat and it was open. At least it did what is was advertised. It failed open. Now I have a 190 degree thermostat from NAPA in there and all is well again.

just my 2 cents,

Tim Swanson
78 midget
73 MGB
tim swanson

Tim-
What temperature is the Moss fail safe thermostat?
N. Phillips

You can get Fail Safe Thermostats much cheaper at AutoZone, but they still cost alot. I used to work there and tried for a spell to sell them to customers because I thought it was an EXCELLENT idea: If the thermostat should fail, it fails open and doesn't ruin your car. Well everyone kept bringing them back to me claiming they were defective! I could never quite explain to them that if some other part of your car is causing the car to overheat, then you haven't solved the problem, the problem is not the thermostat, and you need to fix that and oh, by the way, you've ruined that thermostat because to save your engine it locked open and I'm NOT giving you a new one for free! I stopped bothering after a while. I dont even have one in my car.

-John
John Elwood

Mr Phillips,

The temperature of the fail safe thermostat that I took out was 180 degrees. That is what the Moss calls the standard temperature but John Twist of Univeristy Motors and also NAPA both say 190 degree is better with todays modern oil and gas.

Tim
tim

Hi all.

I understand that the most common cause of ordinary wax thermostat failure is loss of wax (into the coolant), which tends to cause the thermostat to not open fully (or at all, depending on how much wax is lost).

Loss-of-wax is frequently caused by over heating the stat, so if the engine is overheated once it may overheat more quickly next time as the stat no longer allows maximum flow.

Don
Don

In over 60 years of driving I have experienced several thermostat failures, they have always failed in the open position. Maybe I have been lucky. I don't know the temperature spread between the thermostat rating and point of locking in the open position for the Fail Safe thermostat, if it's only a 20 degrees spread I think in heavy traffic on a hot day the thermostat may lock in the fail safe position with a normally operating cooling system.

Clifton
Clifton Gordon

This thread was discussed between 26/03/2006 and 27/03/2006

MG MGB Technical index

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