Heater Core Delete (bypass)???

I know this is the track section, but still the most likely to be frequented by those that have done this and/or know how...

I am going to pull the heater core to remove the carpet (don't want to cut it) and I would like to not put it back... I would rather have A/C in the southeast than heat (for comfort and defogging).

Do you need to keep the ancillary water pump for the heater and just route the lines through it and back to the engine or can you eliminate the pump as well? If you delete the pump, can you just plug the engine ports at both ends?

Cut the carpet.

You have to remove the entire dash to take out the HVAC module to free up that section of carpet. It's more work than it's worth.

Originally Posted by PEI330Ci

Cut the carpet.

You have to remove the entire dash to take out the HVAC module to free up that section of carpet. It's more work than it's worth.

I probably should have waited for reply for last three hours, but free time is limited, it's too late!


In for a penny in for a pound. I decided I wanted it out anyway and want to get all the unneccesary sound absorbing material out.

Now I am seeing it looks like I need to discharge AC lines to get it out so I may cut it anyway. Arrrgh... Cut carpet or not the heater core is gone now and isn't going back if I can help it.

But for the original question; can I just delete the pump and plug both ends of the coolant circuit for heater at the engine? I am pretty sure functionally it is fine, but I am wondering about causing faults in the IHKA controls.

All you need to do is take the hose that comes out of the back of the expansion tank (#4), cut it down and plug it into the hose that goes to the back of the engine (#5) (it actually goes to the plastic pipe that runs to the front of the engine). Just use a splice that you can get at any auto parts store (I think it's 5/8").

Originally Posted by mrshelley

All you need to do is take the hose that comes out of the back of the expansion tank (#4), cut it down and plug it into the hose that goes to the back of the engine (#5) (it actually goes to the plastic pipe that runs to the front of the engine). Just use a splice that you can get at any auto parts store (I think it's 5/8").

That expansion tank does not exist... I am guessing it is for base e46... those parts aren't listed for M3 page on realoem where I linked that pic.

Yes I can run a hose to bypass the heater core, but I am wondering why not cut the circuit altogether. The main coolant route is within the engine block, that is just a path to the heater. If I plugged both ends I am just wondering: why not?

That said, it looks like there is no weight to save unless you get rid of AC too. The heater core itself is barely over 1lb. The only real reason to get rid of it is one less thing to maintain/break/leak, but if it causes me other problems then that is pointless too... there is a lot of CAN-bus BS that I want to make sure isn't going to be screwed up if keeping AC but deleting heater. Just bypassing the heater core and leaving the tubing extra valve/pump is not something I want to do.

Originally Posted by turbo diesel

That expansion tank does not exist... I am guessing it is for base e46... those parts aren't listed for M3 page on realoem where I linked that pic.

Yes I can run a hose to bypass the heater core, but I am wondering why not cut the circuit altogether. The main coolant route is within the engine block, that is just a path to the heater. If I plugged both ends I am just wondering: why not?

That said, it looks like there is no weight to save unless you get rid of AC too. The heater core itself is barely over 1lb. The only real reason to get rid of it is one less thing to maintain/break/leak, but if it causes me other problems then that is pointless too... there is a lot of CAN-bus BS that I want to make sure isn't going to be screwed up if keeping AC but deleting heater. Just bypassing the heater core and leaving the tubing extra valve/pump is not something I want to do.

Sorry for digging up this thread. Have you done it ? How?

I am currently plugging those hoses on the electric water valve. It has no problem. However, when the climate goes a bit cooler and flapper does it job, I can feel warm air from the vent.

Originally Posted by crayonz

Sorry for digging up this thread. Have you done it ? How?

I am currently plugging those hoses on the electric water valve. It has no problem. However, when the climate goes a bit cooler and flapper does it job, I can feel warm air from the vent.

I blocked the rear outlet in the head with a brass pipe plug in the rubber hose and a hose clamp (it is hackish).

And I went to Napa to get a freeze plug for the water pump... none of the heater circuit is left in the car.

Thank you turbo_diesel. This is a very useful information.

TurboDiesel - how did this work for you? I've doing the same thing in my M3 race car build. Anything that is not absolutely necessary is gone. Ignore the rubbish of not removing the dash etc. As you know (and for everyone's edification) it's a snap. The heater assembly, A/C exchanger totaled 35 lbs. Thats cheap weight savings. Especially on stuff that is not needed. I had everything out in an afternoon. Nothing damaged either.

Originally Posted by turbo diesel

Do you need to keep the ancillary water pump for the heater and just route the lines through it and back to the engine or can you eliminate the pump as well? If you delete the pump, can you just plug the engine ports at both ends?

Great thread for weight loss! Any answers to the above question from OP?

Originally Posted by das86turbo

TurboDiesel - how did this work for you? I've doing the same thing in my M3 race car build. Anything that is not absolutely necessary is gone. Ignore the rubbish of not removing the dash etc. As you know (and for everyone's edification) it's a snap. The heater assembly, A/C exchanger totaled 35 lbs. Thats cheap weight savings. Especially on stuff that is not needed. I had everything out in an afternoon. Nothing damaged either.

Sorry for the late response... It was working fine. I was still driving it on the street all summer 2011 but had no track time. My car has basically been parked since September 2011 waiting on the CSL airbox SNAFU (m3F group buy) and some other things in life that come up so I don't have much experience other than driving the car in the heat and humidity of the southeast that summer and having no issues (don't have viscous fan either).

I plugged the rear hose, and used a freeze plug on the water pump and removed everything.

The only issue that kind of concerns me but I never found a real answer is if coolant temps may be higher in the back of the engine because of the flow rates being affected...I assume that there is no flow in the heater core circuit unless the heater is on, but if that is not the case you may have lower flow rates the further back you go in the coolant circuit.