Poor heat

[E30andy]

Now that its getting cold up here in VT, lack of heat is becoming an issue!


Kind of a weird issue, but here goes:


I seem to be getting decent, but not great, heat to the floor vents and defroster vents, cold air from the center dash vents, and slight heat from the side dash vents.


This is with heater set to max heat, and fan at either 3 or 4.


Previous owner put in new heater core and valve, thermostat is new as well. I bled the system once, did not make much difference.

Temp gauge gets up to just about halfway.


Searching the web, I keep seeing people talk about the "blend door", but I'm not sure what/where that is and how it works.


Any help is greatly appreciated!


Thanks Guys!

[packratbimmer]

Forget about the blender screw. Pull your top radiator hose and fill the fitting (block) and then the hose (radiator). You can also fill at the top heater hose, but the hose is harder to get to. Fill slowly. Warm the car up a couple of times with the heater valve off. All air should be gone from the engine system. Now warm up and try the heat while driving.

[spdracrm3]

Now that its getting cold up here in VT, lack of heat is becoming an issue!


Kind of a weird issue, but here goes:


I seem to be getting decent, but not great, heat to the floor vents and defroster vents, cold air from the center dash vents, and slight heat from the side dash vents.


This is with heater set to max heat, and fan at either 3 or 4.


Previous owner put in new heater core and valve, thermostat is new as well. I bled the system once, did not make much difference.

Temp gauge gets up to just about halfway.


Searching the web, I keep seeing people talk about the "blend door", but I'm not sure what/where that is and how it works.


Any help is greatly appreciated!


Thanks Guys!

Also check for a failed heater bypass valve ,BMW factory recall (usually installed in heater hoses near firewall) they can fail closed or partially closed reducing heat output

Sent from my SM-G360V using Tapatalk

[muuris]

Previous owner put in new heater core and valve, thermostat is new as well. I bled the system once, did not make much difference.

First check that the heater core hoses are not reversed. The hose from cylinder head should go to the bottom connector of heater core (near firewall).

[E30andy]

Cool thanks guys! Great suggestions!

I will let you know how things go...

No start this morning so I need to figure that out first! Ugh....

[E30andy]

Car is running again, weird issue....the fuel pump electrical connection was loose. Just jiggled it and it whirred back to life.

Anyway, back to my heat issue.

So I re-bled the system (didnt help, still only getting not very hot heat at the floor and defroster, cold air through the dash vents), and checked the hoses going through the firewall and they looked good.

I have not tried checking the heater bypass valve, which the previous owner claims is new, but I am getting desperate, so that is my next task.

Any tips on how to check it?

Thanks!!

[spdracrm3]

Car is running again, weird issue....the fuel pump electrical connection was loose. Just jiggled it and it whirred back to life.

Anyway, back to my heat issue.

So I re-bled the system (didnt help, still only getting not very hot heat at the floor and defroster, cold air through the dash vents), and checked the hoses going through the firewall and they looked good.

I have not tried checking the heater bypass valve, which the previous owner claims is new, but I am getting desperate, so that is my next task.

Any tips on how to check it?

Thanks!!

Other than feeling or checking at the core with infrared tester. Easiest way is to remove and install a flushing T.if problem is solved you know it's bad

Sent from my SM-G360V using Tapatalk

[muuris]

I have not tried checking the heater bypass valve, which the previous owner claims is new, but I am getting desperate, so that is my next task.

It's actually not a bypass as there is no alternative route -- it just blocks the flow from heater core. It should open when no electricity applied (or connector disconnected), but can be stuck.

Remove, disasseble, renew O-ring and put it back together. You need to drill rivets when disassembling and replace them with small bolts (M4) when assembling.

[Das Delfin]

the blend door you mentioned in your first post wouldn't prevent hot air from going to the windshield or foot panel; that door is only for the mid level vents. It works in conjunction with the temp dial - the temp dial sends an electronic signal to the heater core valve, which lets hot water into the heater core, heating the entire system. At the same time a bowden cable attached to the temp dial controls a flap door inside the heater box that allows outside cool air to mix with the warm air for the mid level vents only. The idea is to allow hot air to defrost and keep your feet warm while providing fresh air to your face to keep you alert.

That being said, I would say first to check your heater control valve since they like to stick, but if you said it's new (and assumedly plugged in and working correctly), then I'd try to make sure the heater hoses are plugged into the correct fittings on the heater core.

Your temp gauge is where it should be. The bypass valve muuris is talking about is deletable if you can find the original hose from realOEM. It was a recall to prevent a failing heater core from leaking scalding hot water onto the drivers feet.

[E30andy]

the blend door you mentioned in your first post wouldn't prevent hot air from going to the windshield or foot panel; that door is only for the mid level vents. It works in conjunction with the temp dial - the temp dial sends an electronic signal to the heater core valve, which lets hot water into the heater core, heating the entire system. At the same time a bowden cable attached to the temp dial controls a flap door inside the heater box that allows outside cool air to mix with the warm air for the mid level vents only. The idea is to allow hot air to defrost and keep your feet warm while providing fresh air to your face to keep you alert.

That being said, I would say first to check your heater control valve since they like to stick, but if you said it's new (and assumedly plugged in and working correctly), then I'd try to make sure the heater hoses are plugged into the correct fittings on the heater core.

Your temp gauge is where it should be. The bypass valve muuris is talking about is deletable if you can find the original hose from realOEM. It was a recall to prevent a failing heater core from leaking scalding hot water onto the drivers feet.

Thanks Das!
I'm wondering again if the blend door is my issue?
I DO have heat at the defroster and foot vents, but NONE at the dash vents-unless thats the way BMW designed the system to work, as you mentioned? My 124 class Mercedes was the same way, only cool air from the center dash vents to "keep the driver alert".

[Das Delfin]

It sounds like your blend door may be partially open, but the heater control valve is what allows hot air to flow to your feet and windshield, and if you're not getting hot air there, your blend door isn't at fault

It's almost like your temp dial isn't telling the heater control valve to completely open AND isn't telling the door to completely shut. But since these two systems are controlled separately I'm not sure how one problem could affect both. You might have to take out your radio and its panel and check out the actuation of your bowden cables to start

here's a diagram from the bentley manual that may help


and another


this from the owners manual


This article may be helpful as well

http://www.e30zone.net/e30zonewiki/images/3/3d/E30_heating.PDF

there isn't a complete solution here, but hopefully this helps your thought process along

[E30andy]

Very helpful, thanks Das!!

[muuris]

the temp dial sends an electronic signal to the heater core valve, which lets hot water into the heater core, heating the entire system.

The shutoff valve has no connection to the temp gauge or any sensor in E30.

The bypass valve muuris is talking about is deletable if you can find the original hose from realOEM. It was a recall to prevent a failing heater core from leaking scalding hot water onto the drivers feet.

I was talking about the shutoff valve, which is the only valve in the heater system originally. As in the pic from ETM you posted, it is controlled by a switch in the temp control dial. As mentioned before, it's normally open, meaning disconnecting either the dial or valve connector makes it open all time -- if the valve isn't stuck.




I've disconnected the valve connector in mine, meaning water is always flowing through heater core. As I live in Finland, this isn't a problem. Yes, it will heat up the dash and inlet air a bit even in the full cold position, but is better for the engine this way.

[E30andy]

Here another clue since I haven’t had a chance to tear into the dash to check the valve and flap.

I notice cold air coming through the slider slots for the air flow direction levers. That can’t be normal!

Any thoughts if that means anything?

Thanks again guys!

[muuris]

Here another clue since I haven’t had a chance to tear into the dash to check the valve and flap.

I notice cold air coming through the slider slots for the air flow direction levers. That can’t be normal!

Any thoughts if that means anything?

Thanks again guys!

Sounds like disconnected or broken tubing inside dash.

You only need to remove the trim above driver's feet and center console to access the valve.