Coolant flow, please comment
 

Please see attached flow diagram i made up ( I know it's a crude drawing ) I'm still working on my monovalve issue (no heat at hwy speeds) Do I have this correct? This is on my 126, 300SD. (new monovalve installed)
thanks for the help.

What car? On 123s and 126s, heat at idle but less heat while moving typically means you need a new monovalve cartridge.

Sixto
87 300D

just edited my post to show my 126, and I installed a new monovalve (cartrage)

Had similar problem
 

on my W123. I found the two-wire connector at the monovalve was corroded and making sometimes/partial contact.

Found a plug at the junkyard and spliced it in. Problem solved. It also solved my "intermittent" air conditioning problem. The a/c was actually working fine but when the monovalve plug was not making contact, the monovalve went to full open by default. The resulting heat overwhelmed the a/c making it seem to be not working.

Thanks Rocky, I've been thru this system (everything) twice, I'm trying to make sure I understand the flow of coolant ( to make further decissions )

Anybody know for sure that this is the direstion of flow in and out of each componant?

You have the basic flow correct.

Thank you Sir

Answer
 

You have e-mail.



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My tech installed a mono-valve repair kit while I was watching. The diaphragm on mine was torn and the screen was a bit plugged.

The "kit" looks like a small, slim steel cylinder with a small diaphragm attached to one end. The cylinder seemed to be sticking in it's "bore" but Mike said "No problem, this part doesn't move."

Installing the kit didn't fix the heating problem. Replacing the valve assembly with another fixed the problem. Is the "bore" the electromagnet and the "cylinder" the plunger?

Thanks!

- Neil

Yes it's an electromagnetic valve. It is a two-state valve similar to your washing machine or dishwasher water control. They cycle it on and off rapidly to modulate the temperature.

To Rocky Racoon's comment above about bad connectors, the nice thing about these connectors is that they are repairable. The housings and plug pins are available from the dealer, or a junkyard plug can be removed, the existing wires unsoldered, and the car wires soldered to the pins, so no inline splices are needed. Everything on the older cars (older than W210) has maintainable connectors. It's also possible to disassemble the connector, dip the pins in tarn-x (use no abrasives, or you'll strip the silver plating), rinse and dry, then carefully tweak with needle nose pliers and you'll be good as new.

You're kidding me.. Really? They modulate the valve this way? I just assumed it was a binary on/off valve... If the climate control is calling for any heat, then it opens to heater core, else don't flow there.

And frankly, in Canada, it would be heating the core most days anyway... So to me was an easy delete consideration if it ever failed I'd replace with straight plumbing or maybe a 3-way brass valve with a summer/winter switchover.

I wonder if this is the source of the buzzing sound I get at different pitches and amplitudess in my drive cycle on a cold day when my climate controls are heating the car? I though the vibrating sounds were related to vacuum pods that are oscillating because they're getting weak or small leaks near some natural resonant frequency point of stresses.

I noticed the monovalve is all rubbery mounted, so what you're saying makes sense and Benz has tried to keep the buzz muted. But if it's modulating I'm going to put a stethoscope on it next time I get a particularly loud hummmm in the climate system. This should help get around the problem of as soon as you open the hood the diesel clatter dominating any other noises.

And I'll take a second look that the valve is not touching anything it shouldn't bumped up against it... I've added a few things in that area for taking more power sources off the battery, for example.

Hi Jay Bob,

Thanks for the speedy reply!

If the new "kit" plunger is sticking in the bore of the electromagnet, what can be done to open the bore a bit to stop the sticking without ruining something?

- Neil

Well, cycling of the monovalve is reverse from what is commonly understood. The monovalve SHUTS OFF water when ENERGIZED and OPENS when DE-ENERGIZED. So basically it defaults to heat. Many have found this out when the system defaults to full heat/defrost.

As far as sticking in the bore, maybe a little polishing would help. It would be a good idea to make sure whatever you use, is thoroughly cleaned before reassembly to keep it out of the system.

Many squawk about automatic climate control but it really is a nice system that works really well. Once I worked the bugs out of mine (re-soldering, monovalve and vacuum pods), it really is a "set and forget" system. All too common is rather than learn how it operates, many rig the system and then complain how it "operates".

Another thing to consider is placing an in-line fuse for the Auxillary Water Pump because it's failure has been known to damage the Pushbutton Controller.

Adding a Fuse to the Auxillary Water Pump wiring was a hot topic a couple years ago. there is no fuse for the Pump, and if it shorts out, then the PBU could get fried.

Remember this Thread?

http://www.peachparts.com/shopforum/diesel-discussion/241899-i-lost-all-electrical-fire-high-up-dash.html


Charlie :xmas: