Wet carpet underneath drivers footwell

[milarsky]

Well, I think this could be heater core, as I have been noticing a small amount of coolant disappearing over time. I have driven around 4500 miles cross country over the past few months, so maybe it was time? Please advise on this issue. I will pull the panels and pull the carpet as well to investigate.

Thanks for the advice,
Jeff

[MyE24]

Heater core or clutch master.
Just need to get under there and look.

[milarsky]

Yeah, not clutch master. Had a looksie.

[milarsky]

Anyone with a spare (new) M5 heater core to sell me? I need it kind of asap, and it could take a month or so to get the part. I would even order one, and send you the new one once it arrives.

best,
jeff

[milarsky]

Also, to change the core, do I have to remove the dashboard or just only the center console?

[Fanclutchnut]

I am researching this job now as I’m about to take out the AC box to redo the floor pan and carpet in ours. It looks the there are 2 ways to do the heater side. You can remove the dash, or do it from below by removing the ac box. If your ac works and you don’t want to evacuate it, you should probably remove the dash. I’m definitely not the authority on this so hopefully someone else can be of assistance.

Also in a pinch, you might be able to bypass the HC by installing a section of tube between the 2 hoses untll your replacement comes in.

[Fanclutchnut]

Also, Rockauto has one left in stock!

https://www.rockauto.com/en/moreinfo.php?pk=6381720

[MattC]

I did this job last summer on my 533 and was able to do it with the dash in place, however, I did remove the A/C evaporator box. I would tend to agree with Fanclutchnut that leaving the Evaporator in place probably necessitates removal of the dash.

[milarsky]

Thanks all! I actually bypassed the heater valve and core, but connecting the coolant hose from the back of the block to the hose from the water pump/thermostat. I am in Santa Fe, so no heat needed until I can get this job done. If anyone runs into problems I can walk you through this procedure.

all best,
jeff

[Preyupy]

watch your water temperature!! By running the water from the back of the block to the T-stat housing you are recirculating water through the block and head WITHOUT it going through the radiator.

When the heater control valve is open the water is going through the heater core and thus cooling the water, When the heater valve is closed the water just goes through the head and through the entire cooling system (including radiator as needed). If you are going to bypass the heater core I would block off the hoses or at least put a restrictor (1/4" hole max) in the line to force the water through the head and the radiator.

[milarsky]

Thanks for this. I am not sure I understand. The coolant is circulating around and around in the block through the front main radiator. Could you explain further? I have only bypassed the tiny radiator in the dashboard. Sorry for my confusion. Also, the water temperature is more stable for sure and is planted dead center, and sometimes moving to the left when the cooler air is forced through.

[Preyupy]

The water path through the heater core is out of the back of the cylinder head> Through the heater core> and directly back into the inlet side of the water pump (through the T-stat housing). This mixes with the water coming out of the front of the head and/or out of the bottom of the radiator (depending on the temp and position of the T-stat)

If the temp starts to climb and you need close to maximum cooling from the radiator the amount of water going directly from the head to pump might be enough to cause an overheating problem. In mild weather this shouldn't be a problem but if you get caught in 90deg + weather you could have a problem.

[milarsky]

Thanks. But I just finished 95 degree days last week here in Santa Fe with no problems and I drove the snot out of the car. I do have an all aluminum radiator, if that factors at all.

best,
Jeff