Heater Control Valve

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Heater Control Valve

Post by 603racing »

I took a chance and replaced my monovalve with a MTC brand. It does not work AND it leaks. I verified there is voltage to the valve, about 6v at highest temp setting. Does this sound accurate?

As for the leaking, it didn't leak until the coolant was up to temp. It just pours out the weep hole now. I am going to disassemble everything, clean really extra good this time and hope for the best. I'm worse off than I was before, at least I could drive the car with no heat but now I can't drive it at all.

In the mean time, have there been any new developments in the area of e24 heater valves? I have read about the e46 valves working. Anything else? Bosch valves seem non-existent these days.
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Re: Heater Control Valve

Post by GazM3 »

I replaced mine with a 12v NO solenoid and it solved all the problems.

1/ when it's off it's totally closed so no warm air in summer
2/ the old valve used to shut down at speed approx 60-70mph so no heat in winter when cruising. Solenoid has no such issue.
3/ solenoid is about 1/3 price of oem BMW valve.

Others who have switched from oem to solenoids at my recommendation have had success as well.

Just search for 12v NO solenoid on eBay then buy 2x commercially available male brass thread fittings with hose bungs on them and use a good thread sealant, then wire it to the supplied relay from the oem wires and then no more problems.
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Re: Heater Control Valve

Post by 603racing »

Awesome! Is there a thread on this conversion?
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Re: Heater Control Valve

Post by 603racing »

Also, does 6v at the valve when at the highest temp setting sound right?
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Re: Heater Control Valve

Post by Brucey »

this thread ought to be in the 'interior' forum along with all the other threads on heater valves?
603racing wrote:Also, does 6v at the valve when at the highest temp setting sound right?
IIRC the valve needs 12V to work.

If memory serves me correctly, weeping from the valve is usually a sign that the valve is not assembled correctly.

http://www.bigcoupe.com/phpBB2/viewtopi ... 11&t=20213

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Re: Heater Control Valve

Post by GazM3 »

I've gotta install my oil/air separator today so I'll take some pics of the valve installed as the plenum has to come out
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Re: Heater Control Valve

Post by GazM3 »

Pics of NO solenoid valve in place.

Image

Image



I dont know why anyone uses the OEM valve
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Re: Heater Control Valve

Post by Brucey »

It is quite likely that any valve fitted to the OP's car won't work if it is only seeing 6V....?

Indeed it is possible that there was nothing wrong with the valve that was originally in there....?

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Re: Heater Control Valve

Post by 603racing »

Thanks for the pics.

Yes, Brucey, you could be right about the 6v. I'm going to test again. Any ideas on what would cause 6v instead of 12v? I verified the temp sensor is connected. The heater control at the temp setting dial maybe?
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Re: Heater Control Valve

Post by 603racing »

Update:

I'm getting 12v at the valve when all the way cold. So that's working, at least for now. I tested the ohms through the windings of the valve, I'm only getting 15ohms. Looks like the electronics of my valve are bad. I put 12v to the valve with it out of the car, it barely moves the plunger.

I verified that everything was installed correctly, the bastard still leaks out the weep hole when the coolant starts warming up and building pressure. MTC junk is really getting to me. I'm going to go with a commercial 12v NO valve.
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Re: Heater Control Valve

Post by Brucey »

I think that ~15 ohms is normal for this valve.

As for it leaking, there is a metal top hat and a single rubber seal between that and the valve body. This seal is the only place it can leak from. I'm not saying this assembly can't ever 'leak because it is bad', but all those I have seen which have leaked have been assembled wrongly (which is easily done) and of course ceased to leak immediately once the thing was assembled correctly.

You can test the thing for leaks using a suction test (using your mouth) or by using a positive pressure inside the thing and soapy water on the outside. Occasionally a leak here in service means that the pressure cap on the header tank is failing (i.e. jamming shut), or that the head gasket is failing, overpressuring the system.

If the valve operates as you work the temperature control back and forth (ignition on) then the control system is probably working OK.

As for the valve 'hardly moving'; this is normal. It is a pilot-operated valve, which is a sophisticated and elegant design. The pilot opens and closes with a small movement, but the main flow is stopped by the diaphragm movement, which only occurs (in response to the pilot movement) when the valve is plumbed in and there is both pressure and flow available.

[ This means that if the heater matrix is clogged, or the pipework is bad, the valve won't work either.....so you need to check that.... but old valves typically fail because the diaphragm splits and then doesn't move in the right way any more. BTW the # thing that causes the diaphragms to fail (apart from old age) is shite - i.e. non standard- coolant... ]

In use the valve is operated in a pulsed mode, on and off quite rapidly. Not all commercial valves are rated for this duty, and indeed the load such valves place on the drive circuitry may be much more severe.

There are millions of the OEM type valve out there operating quite happily in both BMWs and Mercedes (amongst other vehicles). The same kinds of valve workings were used on many later BMWs too. It is possible that the parts you have won't work for some reason but I don't think that this should call for a different scheme entirely.

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Re: Heater Control Valve

Post by 603racing »

You may be correct on the Ohms, I was just assuming that the resistance would be much higher to generate the magnetic field. My conclusion of bad valve electronics was based on not being able to hear the valve operate. Based off of various article I've read, I should be able to hear the valve open/close, but I cannot. If I have the valve out of the car (still assembled) and put 12v to it, shouldn't it push the plunger out? Mine does not.

To your point regarding OEM valves, I agree. I would love to use an OEM valve. I've purchased two MTC's, the first one was seized and I returned it before install. The second leaks for some reason that I have yet to figure out. I'm going to examine it closely to see if the top hat is bent. When I put the OEM valve back in, it does not leak. The diaphragm is torn on it, but the seal still works. The OEM replacement is very expensive.

Maybe I do have an issue with coolant flow. If the valve were not operating, I should have heat all the time.
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Re: Heater Control Valve

Post by Brucey »

the OEM valve is pretty quiet in operation, so don't expect to hear it if there is much in the way of ambient noise.

Mechanically speaking there is very little to go wrong with these valves; the plunger is pulled by a magnetic field against a spring. It has been a little while but IIRC you ought to be able to work the plunger by hand and see if it is able to move freely or not.

The coil will either conduct electricity (and make a magnetic field) or not, so it is easy enough to test this on the bench.

If the coil makes a field, the plunger moves in response to it (again a bench test, but NB dryness or contaminated coolant may jam the plunger I suppose, it is meant to be lubricated by the coolant...) and the diaphragm is intact, the valve ought to work. BTW IIRC there is a filter attached to the plunger, so that particles of crud from the coolant don't get into the plunger bushing. I suppose it is possible that, should the corrosion inhibitors in the coolant be time-expired, the plunger may seize because of corrosion, but I have not seen an OEM unit fail this way yet.

NB when the diaphragm fails the normal symptom is that the valve closes itself at a specific engine speed, so you can have heat at tickover, but not when you are going down the road. Typically this happens at about 50mph road speed. This is because the split in the diaphragm (at first) simulates what the pilot valve does when it is 'closed' even when the valve is powered 'open'.

I posted a nice annotated photo before with nearly all the relevant information on it (in the thread I linked to before), but this website has somehow lost it (along with about a hundred others that I posted.... :shock: ](*,) ). I probably need to post my long-threatened write-up on these valves, because there is clearly still widespread misunderstanding about how they work.

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Re: Heater Control Valve

Post by 603racing »

Great information as always, thanks Brucey.

When on the bench, I put 12v to mine and it does not extend (close) the new or old valve. It moves a very tiny bit, but does not extend like it's supposed to. It's hard to find a working used valve assembly, even if just to test with. I'm going to make a bypass to test that the rest of the heating system is working properly. I plan on doing this by cutting the plunger end off the original valve that failed to ensure the valve remains open. If the rest of the system is working properly I'll likely leave it bypassed until I can find a working used valve assembly.
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Re: Heater Control Valve

Post by Brucey »

as per my previous post, the valve will usually close itself when the diaphragm is damaged.

Also because of the pilot nature of the valve, the stroke of the plunger (when actuated) need not be large; all it has to do is to allow fluid behind the diaphragm, (or not) and the liquid flow does the rest, actually providing the main force required to open or close the valve.

One thought is that it may be possible to repair these valves by replacing (or patching..?) the diaphragm. Obviously butchering the plunger (most likely to no benefit to boot) will prevent this,...

If you just want an 'always open' assembly, why not install a disc of rubber and a disc of metal, backed by the wave washer, backing washer and coil in the usual way?

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Re: Heater Control Valve

Post by Brucey »

BTW the seal assembly etc is retained on the end of the OEM plunger with a small 'C' clip. This can be removed, allowing the working parts of the valve to be removed and (where necessary) fettled.


This would allow the assembly of an 'always open' valve insert rather easily (you just need to make a seal at the top hat in the usual way, either using the edge of the original diaphragm, or an O ring).

If the MTC insert is faithful to the original pattern, you may be able to re-use the original parts together with the diaphragm/main seal unit from the MTC one, and make a workable valve that way.

hth

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Re: Heater Control Valve

Post by 603racing »

We are on the same page. I am going to modify the old valve to act as an always open valve to seal it and let me drive my wonderful car again!
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Re: Heater Control Valve

Post by 603racing »

I modified the OEM valve to be always open. I added another couple washers to put more pressure on the seal and it no longer leaks. Small victory.

Unfortunately, still no heat in the cabin. The hose running from the thermo housing to the T under the intake gets hot, but the hoses running to the heater core and heater valve stay cold. Engine comes up to temp no problem. It appears that I may have a stoppage somewhere. I've never actually dealt with a flow issue in any old BMW I've had. I'm guessing the heater core may be the first place to look... Any suggestions?
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Re: Heater Control Valve

Post by Brucey »

thing #1 to do is probably to flush the heater matrix (both ways) using a hosepipe.

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Re: Heater Control Valve

Post by 603racing »

Need to replace coolant anyway, I'll give this a shot.
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Re: Heater Control Valve

Post by panthercity »

I've recently gone through 2 MTC heater control valve repair kits, neither of which worked. After reading this thread I found a bosch repair kit and it worked perfectly. They are available from FCP Euro for $150.
https://www.fcpeuro.com/products/bmw-valve-64118390132
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Re: Heater Control Valve

Post by Brucey »

panthercity wrote:I've recently gone through 2 MTC heater control valve repair kits, neither of which worked....
in what way did they not work?

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Re: Heater Control Valve

Post by panthercity »

@Brucey
When the MTC units where installed the heat worked below 1500 rpm. Above ~1500rpm the heat shut off.
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Re: Heater Control Valve

Post by brickwhite »

panthercity wrote:I've recently gone through 2 MTC heater control valve repair kits, neither of which worked. After reading this thread I found a bosch repair kit and it worked perfectly. They are available from FCP Euro for $150.
https://www.fcpeuro.com/products/bmw-valve-64118390132

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Re: Heater Control Valve

Post by Brucey »

panthercity wrote:@Brucey
When the MTC units where installed the heat worked below 1500 rpm. Above ~1500rpm the heat shut off.
interesting. That would suggest that either

a) there is a leak past the diaphragm (equivalent at least to a failed diaphragm) or that

b) the pilot stage of the valve isn't working properly or

c) 'something else' is happening.

The construction of the valve is quite simple, even if the operation of it is not intuitively obvious. I wonder if it would be possible by examination to determine exactly what the problem is?

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