Heater core bypass

[PuebloPete]

OK, before everyone starts yelling at me and saying google it, I did. And found probably around 15 threads from here, e30tech and bimmerforums. Here's my issue, a lot explain how to do it, but the problem is that there is no concensus on one way. 50% of the people say to block off the rear port of the engine and run the expansion tank right into the place where the spider hose went. The other 50% says to loop the 2 lines where the heater core was. On the M20, the valve that blocks the heater core when not in use has a bypass line. (Correct me if I'm wrong) From RealOEM there is no bypass line on the S52. So I'm assuming that when the valve is off, it is simulating that the back of the head is blocked off. If the back of the head is blocked off, does the coolant still flow through the head and out internally?

Originally I looped it, but I want to make sure I'm doing this right. Thanks for any input!

[Mr.SWISS]

OK, before everyone starts yelling at me and saying google it, I did. And found probably around 15 threads from here, e30tech and bimmerforums. Here's my issue, a lot explain how to do it, but the problem is that there is no concensus on one way. 50% of the people say to block off the rear port of the engine and run the expansion tank right into the place where the spider hose went. The other 50% says to loop the 2 lines where the heater core was. On the M20, the valve that blocks the heater core when not in use has a bypass line. (Correct me if I'm wrong) From RealOEM there is no bypass line on the S52. So I'm assuming that when the valve is off, it is simulating that the back of the head is blocked off. If the back of the head is blocked off, does the coolant still flow through the head and out internally?

Originally I looped it, but I want to make sure I'm doing this right. Thanks for any input!

Yes, because of where the vavle is located it directs back to through the spider into the thermo housing on the M20. Jlevi and I had it out about this on BF.c as he says it's bad to loop the lines, and I called BS and illustrated how the loop still exists, it's just a smaller loop without the core going from the back of the head back into the spider hose and into the system. Nice to see you're finally putting that E30 back together, I remember the thread on bimmerfest 3 years ago when you tore out the inside.

[jlevie]

This applies to all vechicular engines...

The cooling system is designed such that flow through the heater core occurs whether the thermostat is open or not. That is done to provide full heat regardless of ambient conditions. What that means is that the flow that goes through the heater core bypasses the radiator. If you want to eliminate the heater core the proper action is to plug each of the hoses. If you loop the hoses part of the flow that should go throgh the radiator will just circulate through the block.

The "bypass valve" on an M20 is actually a temperature/pressure relief valve. Early production cars didn't have that valve, but a recall was issued to install the valve to avoid failure of the heater core (and potential scalding) during an overheat situation.

[etxxz]

^^ Really? is that so?.... news to me. i looped it guess i gotta go back and take some corrective action.

[matt]

^^ Really? is that so?.... news to me. i looped it guess i gotta go back and take some corrective action.

Yes, everything he posted is exactly right.

[PuebloPete]

I read so many threads on this subject and not everyone could agree. There must be a "best" way to do it. I think I should go back and block the end of the head. As long as it is still circulating through the head, thats all that matters to me. Its amazing when you read them all, some say I had it blocked and the engine overheated and went back to a loop and was good, others say I had it looped and went back to blocking the port and was good...

So for the record, I kinda agree with jlevie and makes sense that you dont have to wait for the thermostat to open to get circulating coolant thru the heater core. And if that is true, then yes, you could possibly get a percentage of heated coolant back thru the engine. When the heater is on, its acting like a radiator anyway.

Swiss, I haven't been on bimmerfest in a long time. About as long as this freakin build!! I see you graduated to MR Swiss.. ha ha..

[PuebloPete]

I feel like there is no definite answer. Can anyone tell me how the coolant flows through the S52? I'm an M20 guy.... used to be.... haven't dug into an S52 yet. Thanks!

[matt]

The definite answer is in post #3 of this thread.

[PuebloPete]

The definite answer is in post #3 of this thread.

Yeah? So when the thermostat is closed, does the coolant flow thru the head to the back of the head and into the heater core and back? Or the other way around?

[Mr.SWISS]

Here's the scheme. As you can see swapping out the heater core for a length of hose does absolutely fucking nothing but take a teeny tiny radiator out of the equation. One designed for comfort, not maximum heat dispersal.

[PuebloPete]

So if I do this, then it is safe to say that the red arrows I had drawn in there is correct, right?



Thanks

[Mr.SWISS]

That's what the others are saying. It doesn't make sense to me as the water from the rear of the head needs to go through the heater core and into the spider hose to get returned into the thermo housing and recirculated back into the system via radiator or back into the block. I say run a length of hose instead of the heater core.

[PuebloPete]

What I have read somewhere though was that the valve thats mounted at the heater core has no bypass. So in the summer when you have your heat off, its simulating the same thing the diagram I posted?

[matt]

That's what the others are saying. It doesn't make sense to me as the water from the rear of the head needs to go through the heater core and into the spider hose to get returned into the thermo housing and recirculated back into the system via radiator or back into the block. I say run a length of hose instead of the heater core.

No it doesn't. When you have the heater valve closed, there is no flow through the heater core. There is no bypass for the heater valve.

With the heater valve closed, and the thermostat "cold" the coolant circulates ONLY through the block and head.

Have you ever wondered why head gaskets have different sized holes in them front to back? So that the coolant flows evenly between the block and head.

[PuebloPete]

Matt,
Would you say my diagram is correct?