Damaged mono valve pictures please - Page 2 - PeachParts Mercedes-Benz Forum

pawoSD · #16 08-12-2009, 01:31 AM

Near the battery behind the firewall.....or right near the battery, depends which version of the valve it has. Later cars had a different style heater valve.

whunter · #17 10-08-2009, 11:58 PM

Looking for more pictures.

gradyg3 · #18 10-09-2009, 12:16 AM

my heat comes on for about 2 minutes and then slowly fades to cool air so assuming ti is the monovalve. where is it located on a W123?

ajrn · #19 10-09-2009, 12:33 AM

on my 300SD (also a w126) it was in the "rain tray" in the cowl/firewall..

It's a square about 1 1/2" on each side.. It has a screw in each corner, and the top of the solenoid, is a more polished metal.

The swap out took me about 10 minutes, removing and reinstalling one from my "donor" and putting it in my "driver.."

Nice to have heat, again..

AJ RN

whunter · #20 10-09-2009, 12:54 AM

Quote:

Originally Posted by gradyg3

my heat comes on for about 2 minutes and then slowly fades to cool air so assuming ti is the monovalve. where is it located on a W123?

Engine compartment bulkhead, near the battery.
Follow the small hose from the engine water pump to the bulkhead.
Picture attached.

gradyg3 · #21 10-10-2009, 11:17 AM

I'll get on it before the not so chilly winter sets in here in SoCal. Nice to have a bit of heat and defrost regardless.

funola · #22 07-28-2010, 07:21 PM

I've been getting heat intermittently in this heat wave so I will be looking into whether the monovalve is the problem. I have constant voltage to it so must be a leaky or partially jammed monovalve.

As a temporarary fix, I was thinkng of putting a ball valve between the monovalve and the aux coolant pump. Should that shut the heat off? It would go in place of the foot long steel coolant pipe between the monovalve and the aux coolant pump. Why is that pipe there anyway? What's its purpose?

If I take the mono valve apart I'll shoot some pics.

funola · #23 08-05-2010, 10:52 AM

Here's pics and a video of my mono valve. The seals look ok, just dirty with spider webs and corrosion on the outside. Pics are before I cleaned it up with soap and water and 400 grit paper. I will There is a plastic check valve which allows one way flow only. The video (click to play) shows the plunger movement. It draws about 0.85 amps.

vstech · #24 08-05-2010, 11:12 AM

mine was stuck open, I pulled a spare from the parts yard I own...
I'll get some pics of it's open state, and how the valve looks... soon...

bamba · #25 12-07-2010, 07:04 PM

Bad monovalve pulled from my wagon. Note the torn diaphragm. My symptom was little to no heat output over 45 mph.

Below is a good monovalve. I pulled this from a local yard. Note the firm, intact diaphragm. Now my heat is nice and hot on the highway

.

Hope this helps...

muleears · #26 02-14-2011, 05:19 PM

On mine the diaphragm was good, the gasket was good but the screen was plugged solid with crap. I flushed the cooling system when I got the car a few months ago but apparently didn't get this. Another reason to keep your cooling system healthy. On my car the only choices I had was full heat or off. Now with a rebuild kit in my monovalve I have cool air coming out of the vents! Now, to get it to come out the right vents...

paulem · #27 02-14-2011, 06:05 PM

My heat was weak so I unplugged the monovalve and now I've got full heat. I have a new part, but when I went to change it this weekend it seemed like I might lose a lot of coolant and didn't have time to drain/refill. It's pretty high up in the system, I didn't expect so much . . . how much coolant needs to be drained to get this thing out?

muleears · #28 02-14-2011, 07:00 PM

I didn't lose any. The engine was cool and parked on the level ground. My car is an 83 SD if that makes any difference.

bamba · #29 02-14-2011, 09:07 PM

Quote:

Originally Posted by paulem

My heat was weak so I unplugged the monovalve and now I've got full heat. I have a new part, but when I went to change it this weekend it seemed like I might lose a lot of coolant and didn't have time to drain/refill. It's pretty high up in the system, I didn't expect so much . . . how much coolant needs to be drained to get this thing out?

I forget if I swapped mine when the motor was hot or cold, but I only lost maybe 1/2 to 1 cup of coolant. Just a little splash out the top. You shouldn't need to drain any coolant at all. Just pull it out, expect a bit of splash (eye protection!), and put the new one in. You can top off your coolant afterward if you're really worried about it.

whunter · #30 02-15-2011, 01:52 AM

Quote:

Originally Posted by paulem

My heat was weak so I unplugged the mono-valve and now I've got full heat.
I have a new part, but when I went to change it this weekend it seemed like I might lose a lot of coolant and didn't have time to drain/refill.
It's pretty high up in the system, I didn't expect so much . . .
How much coolant needs to be drained to get this thing out?

Trick:
Open the coolant system cap FIRST, to release any residual pressure.