Running w/o heat isn't fun & we have been lucky with this weather, so I put this off....

I was looking at Mono valve repair kits, and as others pointed out, the prices are all over the place. PP MTC kit is cheap @ $15. MB part is ~ $128.00....

MTC feedback is 1 thumb. MB part get 5 thumbs. (both ask you to be the "first to rate this product".....what?)

So here's where it gets interesting....went to my Indie today. His distributor has the MTC repair kit for $120.00......Really?

He says the distributor is great at returns (when needed) and never give him a hassle. How does that benefit the customer?

So I check eBay. Two vendors selling @ $28 & $35.....what gives.

Anyone with experience on the quality of MTC or MB parts care to comment?

I will probably disconnect the power to the valve and get warm while I get feedback from the group.

Signed Perplexed (and cold)

For 8x the price, Id sure be going with the less expensive one.

__________________
1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."

theres another brand available on the auction site. vollig? i bought one.. it's been working OK for a month. dunno where it's made. i've read the mtc are really low quality

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1981 NA 300D 310k miles

The monovalve fails in the OPEN position. This means a monovalve with a ruptured diaphragm or one that is not responding to a voltage input will result in full and uncontrollable heat.

No heat is not a monovalve issue. Check the pushnutton control unit or the auxiliary water pump.

The reading I did said voltage excitation keeps coolant out of the heater core, thereby diverting back to the engine.

OR the broken diaphragm will cause it to leak past, thereby heading back to the engine/water pump and not heading to the heater core and giving up it's precious heat....no?

ADD is kicking in.....

Not true. A bad diaphragm can result in no heat at higher rpm's.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

A torn diaphragm allows coolant to get behind the diaphragm where the dynamic pressure that comes with higher rpm overcomes the pressure of the monovalve spring and closes the valve. There are dozens of reports on this forum of "no heat at highway speeds" that were reasonably attributed to torn diaphragms.

full heat, no heat, low heat, and other heat related issues can all be attributed to the monovalve failing in one way or another... other things can also be responsible, but the monovalve can indeed fail with all of these symptoms...

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I ordered an MTC for my '86 w126. It is made in India. It looks to be on the low quality side. It cost 28 bucks. I will buy a MB monovalve also just to have ready when this one fails. Buy cheap - Buy twice.

__________________
1986 560 SEL
1960 Ranchero
1970 Cougar XR7
2002 Crown Vic Sport
1992 F150

Based my statement on literature, wiring diagrams and experience.

Had an issue with an M117. It was clearly a ruptured diaphragm. Replaced (kit) and fixed.

Had an issue with an OM617. Insert appeared good. Manifested as full heat anytime it was turned on. Also found air conditioner not working. This one was hard to find. Turned out to be a broken wire inside the monovalve connector. The air conditioner issue was also corrected by fixing that wire. It seems there was nothing wrong with the air conditioner. The full-on heat simply overwhelmed it.

Love these wacky old Benz's.

I have had 3 MTC valves fail since May. Two had tiny tears I could see, and the third was undetectable (even with my cheaters on). It failed somehow because coolant poured out from behind the rubber diaphragm.

BUY the OEM. Best price I could get was $108. I got a refund for the 3 POS MTC's.

Jon

'85 300D 102k

PS: I replaced the aux pump with an MTC replacement pump in November. Exactly 3 driving days later, in the middle of Nowheresville, Indiana, my temp gage (which is religious at 90) went to 110 and started jumping around from 85-115. Opened the hood, and the entire right side of the engine compartment was covered in coolant. The new MTC aux pump was leaking at the joint between the motor and pump. There are 4 phillipshead screws holding the pump together. I turned them all at least a 3/4 turn. Leak is solved, but I am watching it. Too bad the only coolant I could get was GREEN...ugh.

Where did you find a OEM monovalve for $108. All I seem to find are complete new ones for $220 or MTC rebuild kits for $19.

Much Less MTC junk in this case.

Either:
Bosch "Made in Hungary" or "Made in Germany"
Or
O.E. Mercedes.

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'84 300SD sold
124.128

MTC = Mission Trading Company = Junk. Pretty close in kwality to Uro/APA/FEQ which are the worst of the junk.

I'm actually surprised that an MTC part was made in India, I'd expect the majority of their stuff to be Chinese.

Mission Trading Company | MTC | Wholesale Supplier for Discount Car & Truck Replacement Parts | Engine, Suspension and Mount Part Manufacturer

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

At $108, it was just the OEM kit, not the entire monovalve. It came in a MB box, and was labeled as made in France. I had to wait three weeks to get it....backorder.

It has been working flawlessly cycling hot and hot as it's supposed to. I do think I need to check the air supply tube to the thermister, as it is a little slow to change temps.