Hooked up bypassed heater core, some problems

[Reuben Lim]

Hi all. Hooked up heater core for my 89 525i a US version, which was bypassed by PO, thought this was reason why I have persistent idle problems especially when engine cold; it wasn't, still have this problem. Now have heat coming thru front vents, problem though is that I lost cooling at the rear vents, and there's this slight coolant smell from there, too.

The aircon guy says he would have to remove the dashboard to solve this problem. Any way I can solve this without going through that, worried this could screw up my electricals. May just re-bypass the heater core, am in a tropical country anyways.

[uscharalph]

Hi all. Hooked up heater core for my 89 525i a US version, which was bypassed by PO, thought this was reason why I have persistent idle problems especially when engine cold; it wasn't, still have this problem. Now have heat coming thru front vents, problem though is that I lost cooling at the rear vents, and there's this slight coolant smell from there, too.

The aircon guy says he would have to remove the dashboard to solve this problem. Any way I can solve this without going through that, worried this could screw up my electricals. May just re-bypass the heater core, am in a tropical country anyways.

This is a very labor / time intensive repair. If you don't need the heat, just re-bypass the heater core. Mine is bypassed till either I get enough time to do it or am willing to pay $700 - $1000 (Just a guess) to have someone else do it.

[shogun]

Reuben,
the heater core has no influence on cold idle.
When engine is cold, the large coolant cycle is closed first and is only circulating in the small cyclie = engine, and thermostat is closed.
If you do not need the heater core in your nice tropical country Philippines, by pass it.
As for cold behaviour of the engine, check for air leaks, check the temp sensor for coolant and intake air, maybe also the injector seals.
All these things are 'shrinking' when cold and expanding when at proper running/operation temperature.
That is why leaks mostly are noticed when engine is cold.

[Reuben Lim]

Ok Erich, thanks for the idling issue heads up, but would really want the car returned to stock, i.e., heater working, am a bit weird about wanting everything in the car, even the littlest switch, to work (save for those the funny-sized cigarette lighters, and some rows in the rear window defogger, they all do). Do go up to the mountains occasionally, and there it's cold enough for the heater to be useful. Any ideas on what could be causing the lack of cool air and the coolant smell coming from rear vents? But if there's a lot of possible causes, and it would cost me a bundle to fix like Ralph said, will most likely just go back to the bypass. Cheers!

[genphreak]

The smell is the Heater core or connecting hoses leaking. They crack/rust/break and cost about US$160 new I think and u need the pipes adn o-rings with them. But you have to take the whole dash apart to change them as uscharalph said... Nick

[Paul in NZ]

the rear vents (at the back of the console) only pass air from the outside dont they.Only the floor vents have heat or cooled air....

[Reuben Lim]

That's new to me. Will have to check around for parts, see how much the whole heater core thing will cost me. Will probably just bypass the thing again. Cheers!

[shogun]

But contrary to older instructions - here the first one on the net from Stefan Borch- it is not necessary to remove the whole dashboard but just the lower part. 1 day complete or let's says a weekend and it is done. My friend here made it in 7 hours on his E32 735. But if you make it the first time, take your time, make fotos of all the parts and notes where and how they were installed. Makes it much easier for assembling again. The cost is not that much, just the time.
Maybe similar to the headliner. Before I did that one the first time I was really wrried how to do. Took me one Saturday from 10-18 H. But actually is was quite easy to do, just a time factor.
Prepare yourselves good by copying papers with instructions, have more than necessary spare parts on hand (that takes most of the time, when you suddenly notice that some simple gaskets or clips are missing and the shop is 30 miles away or closed already.), and friend who can give you a hand, tools and TIME. Make a break in between and relax and then the start again is much easier.
Here some info from Stefan
http://www.homeofsbc.com/Fixes/Heater/heater.htm

[uscharalph]

But contrary to older instructions - here the first one on the net from Stefan Borch- it is not necessary to remove the whole dashboard but just the lower part. 1 day complete or let's says a weekend and it is done. My friend here made it in 7 hours on his E32 735. But if you make it the first time, take your time, make fotos of all the parts and notes where and how they were installed. Makes it much easier for assembling again. The cost is not that much, just the time.
Maybe similar to the headliner. Before I did that one the first time I was really wrried how to do. Took me one Saturday from 10-18 H. But actually is was quite easy to do, just a time factor.
Prepare yourselves good by copying papers with instructions, have more than necessary spare parts on hand (that takes most of the time, when you suddenly notice that some simple gaskets or clips are missing and the shop is 30 miles away or closed already.), and friend who can give you a hand, tools and TIME. Make a break in between and relax and then the start again is much easier.
Here some info from Stefan
http://www.homeofsbc.com/Fixes/Heater/heater.htm

Nice Diagram, Shogun!

[Reuben Lim]

Exactly what I need, thank you kind sir.

Went through the well-documented slow and the quick fixes, will study how to attack this. Or not. Yikes! May be beyond me, but will try to muster enough resolve (and helping hands) to do the job. Or at least watch with a beer in hand from the sidelines. Cheers!