M42 problems

[E30ruben]

Honestly, I have no idea. But that's how it was Everytime I pushed it to touch the frame it he car started.

[E30ruben]

Any help on the heater problem?

[oldmann]

Sounds like thermostat issue, sticking open, or failed open. Too much flow through the radiator, not enough heat in the coolant to make the heater effective.

[E30ruben]

But how come my car runs between 1/4 and half unless I sit in place it stays right at 1/2.

[oldmann]

Guage should read the same whether moving or not, once operating temp. is reached. My M42 shows just short of 1/2, always, once warmed up. (190 degree thermostat)

If thermostat is stuck part way open, coolant is flowing through the radiator constantly, the thermostat should cycle open and and closed to maintain operating temp in the engine block.

It takes heat in the coolant for the heater to be effective.

Use some kind of thermometer to find out actual temp. your engine is running.

[E30ruben]

So I should probably start by changing the thermostat..

[oldmann]

I don't like to tell anyone to change parts to fix a problem that hasn't been fully diagnosed.

We don't know if its the thermostat, secondary thermostat, heater control valve, (or its control) or plugged heater core, or combination of these.

Fix only whats broke, and replace or repair that, Throwing parts at it is too expensive.

1st is too find out if engine is at operating temp, around town and then on the highway. If it is, then look into the operation of the secondary thermostat, then control valve and its controls, and whatever else might keep hot water from passing through the heater core.

[E30ruben]

What's the secondary thermostat? Ive never heard of that.

[E30ruben]

Anyone?

[bmwman91]

I believe that the secondary thermostat is a retrofit part that was installed as a bypass on the heater core hoses to protect against allowing over-temp'ed coolant into the heater core (and subsequently rupturing it).

[oldmann]

bmwman91 is correct. Its located below TB and towards firewall. inline from the heater core.

Mine was gummed up, not closing all the way, would let coolant bypass the heater core. Removed it, cleaned it, and CK'd for operation on the kitchen stove, in a pan of water (wife wasn't home) worked fine after the cleaning.

[firstE30]

"wife wasnt home" lol!! I got caught using the oven to clean some oil engine parts. It was bad. :(

[oldmann]

Stove, Oven, Kitchen sink, OFF LIMITS for car parts, (when she's home);D

Heating up bearings in the oven just before Thanksgiving was a bad idea.