Heater core thermostat ?

[Bmjpv]

On my 91' Ix I have a inline (engine side of the firewall) factory thermosat before it goes to the heater core. On my 88'Is, At the time when I installed a S52 ,I remove that one . Question ,Is it really a thermotat? Does it really have to be there ? and What does it really do besides put another flow restriction in the heater system?? Thanks, Joe

[jlevie]

The is a temperature and pressure relief valve that was added to some cars as during a recall. I don't remember if was ever part of production. The intent was to prevent excessive cooling system pressure from causing the heater core to burst and release scalding coolant into the cabin.

[Bmjpv]

Ix heater

So if it's a pressure relief setup (I had heard that too) do I really need it In my Ix ? Am I wrong in thinking it's some kind of a thermostat ? I have to crank the heater control valve over to about the 3-4 O'clock to get that heat to pump out. I also installed new 189' thermostat at time of t/belt and water pump. I get a lot more heat out of 88' 24v (this valve removed) than my Ix. Any of this right ? Thanks, Joe

[jlevie]

The pressure relief valve might be introducing a slight bit of restriction, but I doubt it would introduce enough to cause what you are experiencing. A clogged up heater core, a bad hose, or a bad heater control valve are obvious suspects.

[Bmjpv]

I was hoping you would say I was right in what I was thinking but I think your answer is most likly the correct one. I'll start looking into it . Thanks for the answer. Joe

[Liam]

The Aux. thermostat goes in the hose that comes off the back of the head and into the upper heater tube (there is an arrow that should point from the engine to the core).

The heater hose that goes to the lower heater tube and to the suction side (under the manifold) gets the "T".

The small hose goes from the Aux. thermostat to the "T".

It's purpose is to bypass the heater core in the event of an overheat.

Also with this recall the 2.0 bar cap was replaced with a 1.4 bar cap.

Is it necessary? I don't know.

I have never seen a heater core burst like they were reported to that prompted the recall, but the Slide Rule Boys at BMW sure thought so.

But it does not reduce the flow (if it's working correctly) under normal circumstances.

[Knockenwelle]

I always thought is was to prevent too-hot coolant from circulating in the htr core and burning tender feet with too-hot air. I also thought it was waayyyy too heavy and complicated to reinstall.