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Discussion Starter #1 (Edited)
Hey everyone, back on with another DIY. This one addresses the $400 used and you don't want to know the new price, heater control valve in my 2000 740i and others equipped with it.

Once the car warms up the AC can't keep the car cold. Source problem is the heater control valve stuck open. You can buy a retrofit kit from eBay for $50 to fix the unit, but you must be extremely careful, there are sensitive electronics that must be juggled while opening and sealing unit back up.

There are two heater cores in the car and thus the extra line back there to the cabin. So after wrestling the until out after detaching two electrical connectors and three screw clamps using a long 1/4 drive extention and an 8 mm socket, set it aside to renno at your leisure after you install the following creation of mine.

Bought at Menard's on my way back from the boat today:

(2) 3/4" copper pipe 90 degree elbows

(1) 3/4" copper straight extension

(1) small tube/tub pipe Flux

(1) Flux application brush

Pipe extension is too big to fit inside large end of the elbows. The large end is too big to fit inside 3/4" opening of rubber hoses to and from engine. Solution is to section the straight extension by cutting an 1/8" strip out of it lengthwise with a cut off wheel then use a section of 3/4" O.D. pipe or steel rod stock to clamp it and hammer it round to fit inside two elbow sections. I cut 1/2" of the straight extension so the finished product was compact to keep hoses neutral and not kinked when installed.

Apply Flux to the inside of each elbow and make sure joints are tight and square. Heat with small butane torch the size at least of your fist (pencil torch will be too small), until smoke from burning flux stops. Wipe joints with metal pipe solder and hot copper will draw the metal via capillary action.

It will take some finess, but after a foot of solder is gone, you should have all the joints sealed. Don't apply the flame to the solder directly, it will just burn up and drop away and be wasted.

I left a gap so that I could add a strip of JB weld putty to be ground smooth later with a flat file. It's hard to keep the solder flowing in such a piece and my smaller torch and anytime it cools and solidifies, there could be a seam again against the next layer of solder. The epoxy putty just makes me feel that I was looking ahead for leaks and not fixing them after the fact. Life taught me to be pessimist by policy and optimistic by attitude.

The offset angle you see in the image was from doing a test fit before soldering to see where the hoses wanted to orient to keep them neutral and have uninterrupted water flow. The sides of each elbow are connected in tangent via an imaginary line in space, if you want to copy mine without having to test fit.

Now I can have the car back on the road while I fiddle with that unit and not have to worry about losing my coolant or it not working right and killing my cabin cooling for this hot summer season. I blocked of the heater core nipples with three fingers cut from black neoprene gloves and three black zip ties. I don't want corrosion or debris getting in there while I fix the heater control valve when I get the parts and have the time to jump into it.

I make no warranty for the design. I install it at your own risk. Hope it helps someone get by until they can get a more permanent solution.

How I know about this stuff is that I used to own (partnership offered for accounting work helped win us a Boeing contract ) a machine shop that machined metal blocks the size of a big rig trailer, vertically. Largest capacity mill east of the Mississippi. NAFTA killed that industry dead. Korea and Eastern Europe ate our lunch after Clinton gave away the keys to our industry.

Debbie

Edit : $7 out of pocket if you already have a well equipped home shop/garage.
 

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Discussion Starter #4 (Edited)
I'd say no, because that will inhibit coolant flow through the engine. Do you really want to have another reason to overheat and blow up plastic parts? Two hoses leading in, one out.

Edit: I see you are from Maine. Summer is only a few weeks there. Carry on.
 

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Discussion Starter #6
Summah, that shoht time 'tween muhd seasin' an huntin' seasin, eya deah?

Great people, but the accent is as deep as any southern one. Don't speed over 5 mph there or you will get a ticket, especially with out of state plates. Littering is seen as felony territory too. Every fall kids up to grandma driving everywhere in blaze orange. Wave hello to everyone as they pass on the road. It's like 1957 Mayberry U.S.A. in most of their towns and villages. Subarus and GMC trucks everywhere. If you drive a Ford or gasp Lexus/BMW, they might call you "that high fallutin' girl from away."
 

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Oh my...after the loss of our beloved Bluebee & her posts from the forum...have we been blessed with MIBarbieBlond? I await to read your future threads/posts. :D

Good post...job well done. :thumbup:
 

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Discussion Starter #9
QSilver7, sorry to hear about the loss of a car girl here. We are rare. Have a colleague who was told last week her car had a tire that was going flat. She drove to the dealership at lunch and had all four replaced. "One was obviously bad so I changed them all out for new. I can't drive around on old tires."

I asked her why she didn't just put air in the tire and she said she didn't know you could do that. I couldn't even think of a reply.

Shrek: You might just be! Just kidding. Thanks for the laugh!
 

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Blimey, you could have overhauled the valve in a fraction of the time taken to collect the parts and assemble that gizmo!
 

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Discussion Starter #11 (Edited)
It only took an hour to build. Hardest part was getting heater valve out, for me. Think Betty Draper (first few seasons only, she got BIG those later ones) on Mad Men, standing on her tip toes trying to reach the back of that engine. I didn't want to rush the job and have it fail during summer driving. I have no parts to renno it and want to get the kit with the brass plungers.

$400 used? Ouch! I want to do the job right and there are plenty of warnings to take care around the delicate electronics. We girls always plan and plan and worry some more and never think we know enough. You guys are confident even when you have no idea what is behind the panel you are unscrewing, unbolting or prying apart with the biggest baddest tool you have on hand. Lol!
 

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It only took an hour to build. Hardest part was getting heater valve out, for me. Think Betty Draper (first few seasons only, she got BIG those later ones) on Mad Men, standing on her tip toes trying to reach the back of that engine. I didn't want to rush the job and have it fail during summer driving. I have no parts to renno it and want to get the kit with the brass plungers.

$400 used? Ouch! I want to do the job right and there are plenty of warnings to take care around the delicate electronics. We girls always plan and plan and worry some more and never think we know enough. You guys are confident even when you have no idea what is behind the panel you are unscrewing, unbolting or prying apart with the biggest baddest tool you have on hand. Lol!
There is nothing wrong with the original parts used in the valve. Its what's wrong with owners who don't use the correct coolant, or just plain water, that then allows corrosion to occur. There isn't much to do to them really...

Keep the posts and that sense of humour coming...
 

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Discussion Starter #14
Thanks! Sarcasm and context is hard to convey online. Key and Peele did a comedy sketch about it.

Btw, mine is clean as a whistle as far as the right coolant goes, it's blue and zero residue. They guy had the the radiator and expansion tank replaced. When they did that, the service techs or the rad failure put pieces of black plastic into system and they can be seen deep inside unit with a flashlight.

I might solder a mesh strainer into that elbow if this happens again. These plastic pieces floating around system are warned about on other Internet pages.
 

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Plastic pieces could also be from the water pump, BMW put a plastic impeller in it.
 

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Discussion Starter #16 (Edited)
Sounds right, he listed a litany of parts trying to sell it, water pump was one of them.

Black injection molded thermoplastic as an impeller? That explains a lot. It does not tolerate high temp heat soaking well. Doomed to fail when it has to function near it's deformation zone. There is an off white material that is a much better choice. Similar to cast Delrin in fact.
 

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Discussion Starter #17
It wasn't just the heater control valve.

Now that I've had time to drive it, the ice cold AC at start up now goes cabin temp air after a few minutes of idling from instead of hot after few minutes.

More goggle-fu and I find my auxiliary fan is not switching on when AC is selected. Thus the compressor is commanded to switch off once condenser temps get too high.

Looks like a resistor might be the culprit, though it seems the 99 and up are different with some sort of computer controlled speed settings, through a variable resistor?

Need to test the fan first and make sure it is plugged in and works via direct 12v power from an outside source.

Any ideas for parts. It looks like it might be a $300 fix via OEM.
 

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Discussion Starter #18 (Edited)
My $1,800 project 2000 740i in all its 87k mile glory

My hard top cabin cruiser boat and pole barn in background. Surrounded by subdivisions and posh open air shopping malls, but I've got acreage and scenic waterfront views. Dreadfully cold winters, so this project car is fun to tinker with when there isn't much to do.
 

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Discussion Starter #19
Looks like no resistors on my car for the auxiliary fan. Relays, fuses and DME (engine control unit) are next on the list of culprits. I get a high pitch whine when I put then key in position 2 (run) but don't start the car. Is this injector and fuel system noise/throttle body noise or a bad DME? Online says engine whine is actually a bad computer. Sounds like I need to run some checks. Time to hook up a code reader to the engine bay and start a new thread once I get some clues about what is going on in the background with this car. Project indeed. Glad my LS400 is so reliable with nearly the same type of layout and V8. They look like brother and sister next to each other in the garage. One is an evil boy though! Lol.
 
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