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1991 560SEC
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Discussion Starter #1 (Edited)
Recently John posted a very good thread about the combination between the aftermarket mono valve MTC and MB. The thread can be found here: http://www.benzworld.org/forums/w126-s-se-sec-sel-sd/2497961-mono-valves-meaning-life.html . However, there is a bit more to the monovalve story going beyond MTC, and this thread will look at what’s left: the comparison between the three of them (MTC, Bosch, and BMW) and how each of them fits the heater valve body. Before reading this thread, I strongly recommend reading John’s post FIRST for a better understanding of the below.

Before you start reading, I want to be very clear: below you will find MY personal observations and impressions. I have no affiliation with any of the products below nor I have any monetary gain, and I tried to be as fair in my evaluation as I could. You may have different opinions and disagree, and that is fine too.

The parts that I will use in my comparison are:
- New MTC kit, MTC PN 3065, made in India (I paid $35 on it from EBay, there are also cheaper ones, however be aware there are also different levels of quality)
- New Bosch kit, Bosch PN 1147213007, made in Germany (purchased from Napa 02/2015), currently NLA (paid $ 104 , with tax and shipping included)
- New BMW kit 64118390132, made in France, purchased from FCPEuro (paid $ 135.99 shipping included)
 

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1991 560SEC
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Discussion Starter #2
1. Is it a genuine Bosch, or a just a MTC monovalve?

First, how can you tell just by looking at a repair kit if is a genuine Bosch part, or an aftermarket replica in a Bosch box? What if you find an EBay repair kit, and the seller says is a Bosch? Is any way you can verify is not a MTC? It turns out that the used parts I have (old monovalves with broken diaphragms pulled from MBs) and the new Bosch, they all have (w/o exception) something in common: on the side of the rubber diaphragm I found the raised letters: MB 30-28. The MTC did NOT have that, also the BMW did not have it. Furthermore, the MTC spool does not appear to have the brass wire mesh that the Bosch has, also the circlip on the brass rod does not appear to be made out of brass on the MTC model, see below picture (John mentioned the non-brass circlip too in his post). Based on the above, I concluded with a high level of confidence that the Bosch kit I purchased from Napa is actually the same part that MB used.
 

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1991 560SEC
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Discussion Starter #3
Do they have the same dimensions???

Well, first let’s measure the OD on each kit, as they come out of the box. Below are the dimensions: MTC, Bosch and BMW. Notice that MTC is bigger by almost 1mm. That will cause a problem, shown in few moments. Also please notice that the MTC does not have the brass circlip.
 

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1991 560SEC
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Discussion Starter #4 (Edited)
Let’s build the “hybrid”

As John described in his thread, the monovalve body, circlip and spacer can be used with the MTC spool in order to obtain a fully functional unit. From this point forward I will refer to this new part as being the “hybrid”, because is not entirely a MB, but is not entirely a MTC either. Below are the two pictures showing:
- First picture: the MB (used) parts to be re-used (upper) and a MTC monovalve I was just a bout to take apart (lower),
- Second picture: what is left of the MTC kit (upper) and the new “hybrid” ready to go in the heater valve body (lower).
 

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1991 560SEC
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Discussion Starter #5 (Edited)
How good of a “drop-in” replacement will the hybrid become?

Well, that’s where the fun part starts, and one of the purposes of this thread… Measuring the OD of the hybrid, we still get more than 30mm. The monovalve seat in which the diaphragm will install has an ID (Internal Diameter) of 30mm (red arrows pointing). At this point forward expect that issues may occur with the hybrid because its OD is greater than the seat’s ID which means you may have trouble seating it right in the heater valve.
 

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1991 560SEC
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Discussion Starter #6 (Edited)
How does each of them fit?

Below please see (in order) the Bosch, the BMW, and the MTC. As expected, the MTC does not offer an easy fitment because of enlarged diameter that does not allow the monovalve to seat properly in the corresponding seat of the housing. The Bosch and the BMW had no problems in that respect. If the MTC is forced w/o having its diaphragm helped to fit correctly (task that tested my patience and took me two years ago about 15 minutes), it will be forced to roll its edge in order to fit into its housing seat when the monovalve is pressed down, it will still seal against the coolant, but the rubber will be stretched and stressed, which in turn will contribute to premature rupture of the diaphragm (on top of the fact that its rubber does not appear to be high quality to begin with).
 

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1991 560SEC
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Discussion Starter #7 (Edited)
Are there other differences between the hybrid, Bosch, and BMW???

Well, actually there are:
- The rubber diaphragm acts like a bellow. From the first picture below (from L to R: Hybrid, Bosch, and BMW) you can see that the BMW has “more bellow” than the other two. Is also my opinion that the quality of the rubber is a bit better on the BMW than on the Bosch
- The MTC rubber diaphragm also looks a bit cheaper than the other two. In fact even the injection mold was a cheap part, not meant to generate too much quality to begin with. Note please the circle marks (the round circles on the diaphragm’s surface) which are nothing else but tooling marks from the mold manufacturing process. Such marks are not present on the Bosch or the BMW diaphragm.
- My biggest surprise (initially I assumed that the Bosch and BMW are actually the same Bosch part) came when I looked under the diaphragm: the BMW has an extra rubber washer that the Bosch does NOT have (green arrows pointing). That extra part has the purpose of reducing the stress that the brass washer would put on the diaphragm and the direct contact between the two parts. In addition, without being an expert in rubber parts by any stretch of imagination, is my opinion that the BMW diaphragm is a bit thicker and the rubber used appear to be a better quality than the Bosch.
 

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1991 560SEC
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Discussion Starter #8 (Edited)
In conclusion …

1. There are ways to correctly identify the MTC, Bosch and BMW monovalves.
2. The MTC is a lower cost replacement, and its quality is reflected by the price. I don’t expect great life out of it, is not made to last. The parts that were not used in building the hybrid appear also low quality by comparison with the similar MB used parts. The only surprise I had was that the spring of the MTC appeared to be a strong one, maybe even a bit stronger than the Bosch. John saw exactly the opposite, so don’t throw away the MTC until you make sure the hybrid works fine.
3. If the MTC is your only option, when you install it make sure you will fit the diaphragm correctly in its seat. Do not put back the rest of the parts until you are sure it seats correctly into its seat.
4. The Bosch (if you can still find it) is good quality at a decent price, it appears to be exactly what MB used.
5. The BMW part does not appear to have the same components as the Bosch, and I am under the impression that either the BMW is made by Bosch under specific BMW standards, or is made by someone else, perhaps even BMW.
6. The BMW appears to have the best quality overall and a bit better design. In my opinion it would be the best choice for a long lasting solution, but unfortunately I cannot advise how it would perform (my car will not run for at least one more year). If you can afford spending the money, this appears to be the most reliable solution. It would be nice if a member will use it and share with us his impressions.

Thank you for reading.
 

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87 Euro500HVSEC. 88 Euro 560HVSEC. 89 Euro 560HVSEL
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I have the duo set-up in both my coupes with the dual cabin control temp wheels for left ad right side.
It would be handy to know who can supply the repair kits for the Duo Valves?
 

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1991 560SEC
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Discussion Starter #12
Nicely done Roy. Thanks for taking the time and making the investment to help with this perennial problem.
I am glad I could help. Reading it all means you did not fall asleep reading.:grin

Actually John should get some credit too, I did not think of it until I saw his post.

I decided to make the investment after I noticed that the Bosch is NLA, not even at Napa. I was afraid the same may happen with the BMW monovalve, so I bought myself one. Our brothers from BMW are using them too, so its future availability may be uncertain.
 

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350SDL, '17 GLS450, "Grandpa's Roadster" Project Car
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Good writeup!

The duovalve uses two monovalve kits (go figure...)

Interesting about the difference in OD. I did not take any special care when installing my "hybrid" valve kit. That said, I doubt I got it in correctly, although it continues to work... (Antifreeze is very slippery...)

Did you actually measure the spring tension? What did you get? I'm very surprised you found the MTC to be as strong as (or stronger than) the Bosch valve. My MTC kit is (was) over 1 year old, so maybe they got the message?
 

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1991 560SEC
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Discussion Starter #14
Thank you, John.

If it does not fit correctly but is installed w/o noticing, it will still work and seal, but the diaphragm will be already stretched a bit on one side. That will shorten the life of the diaphragm because when the spool will move it will stretch it even more. Eventually it will break from the side that was already stretched.

I did not measure the spring tension with a device, only what I could tell from me pulling the spool. It surprised me too. However, my impression is that the MTC box is older than 1 year, and has different graphics (higher price too) than the other MTC I bought two years ago and I installed in the car. Maybe I have a softer spring because of a Bosch defect, if indeed my "fingers gauge" were correct?

MTC (Mission Trading Company) is not a manufacturer, is a wholesale auto parts supplier, so is very possible that the part I have may be from a different MTC supplier than the one you have. Judging by the box, I would say that what I put in the car two years ago is worse quality than the one that I got now.
 

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1991 560SEC
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Discussion Starter #16
Box? I didn't get a box...
The white box is for the kit I bought 9/2013 for $15. The other box (bigger)is what I bought recently from EBay, a private seller of BMW parts, and somebody wrote on it 2/12 and $ 79.95.

Is possible that you got something very poor quality, if it was very cheap. I mentioned earlier in the thread that there are different degrees of quality for the same MTC part.
 

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'91 560SEC, '91 300SE (sold), '98 Yota, '02 S-10 Hauler
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I can attest to this info as Roy educated me with those valves just the other day. It was something I didn't pay attention to when I changed the monovalve in the SE a while back, IIRC it did fit just fine and no I can't remember it's brand
 

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1991 560SEC
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Discussion Starter #18 (Edited)
It was something I didn't pay attention to when I changed the monovalve in the SE a while back, IIRC it did fit just fine
Is not easy to see if it fits or not, you'd have to look inside all around the diaphragm after you place it in the heater valve body to see if it seats right from the very beginning (have a flash light ready). Most people don't do that because they would not expect a problem there (I confess I did not expect that either), and is also not easy to see inside. As I mentioned already, if you add the rest of the parts (washers, spring washer, coil, retaining plate and the screws) it will still seal and work, but as is pressed into the seat by the rest of the parts, the diaphragm will be stressed and would fail sooner.

The best way is to measure the OD of the rubber diaphragm just before installing it: if it comes out to (let's say?) more than 29.85 mm (approximately 1.175"), expect to add extra work in making it sit correctly.

I would be curious to hear the opinion of somebody else who will change it, and find out what the OD was before installing it and if he observed the same fitment issue during replacement. The OD was greater than 30mm on the MTC repair kit as it came out of the box (on two separate MTC kits), and also on the hybrid I built.
 

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1991 420SEL & 2000 CLK430 AMG Cabrio
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I was afraid the same may happen with the BMW monovalve, so I bought myself one. Our brothers from BMW are using them too, so its future availability may be uncertain.
So, is it safe to say that the BMW branded mono-valve will indeed work straight out of the box?
`
 

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1991 560SEC
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Discussion Starter #20
So, is it safe to say that the BMW branded mono-valve will indeed work straight out of the box?
`
It fits correctly straight out of the box. I have my engine out of the car and because the rest of the work I plan on doing on the car (refreshing all engine seals and gaskets, rebuilding all the front suspension, all steering and the heater box, refreshing some of the electrical), I am estimating it will be at least one year before I will be able to have the engine back in the car and start it up. For that reason and in all honesty, at this point I can advise only about its fitment, but nothing about its performance in a MB heater valve.

I am hoping somebody here will buy one and test it, then share the results and impressions.
 
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