M119 thermostat testing, troubleshooting, part numbers

[srdavis872]

So I've had my 94 e420 for about 2 months now. It's got a lot of miles (216k) and needs some tuning up all around. I'm trying to decide if it needs a thermostat or not. The gauge rarely reads over 80, and I've never heard the electric fans kick on (though it has been cool out). But the odd thing is, I've never had a car that produces heat as quickly as this one. I can start it up on a cold morning, let if warm up for 20-30 seconds, and by the time I'm out of the neighborhood I've got heat, and good heat.

I wonder if my gauge is just off, but from what I understand, there's 3 different temp sensors, and the fans and gauges are controlled by two separate ones, so how likely is it that I have 2 bad sensors? Any good way of testing these? None of the sensors nor thermostat are that much, but would like to narrow it down before just throwing parts at it.

 

[gsxr]

If the gauge is accurate, and reads below 80C when fully warmed up, the thermostat is defective and should be replaced. Not likely you have multiple bad sensors. If the t-stat is more than 5-7 years old, it is overdue for replacement anyway. It really should be replaced proactively at every other coolant change... cheap insurance, and they are a pretty common failure. Bad things happen when they fail in the closed position. Make sure you get the correct type... your 94 should use the early version with 116- part number:

 

[srdavis872]

I think it's just wild how quickly I get heat inside for how long it takes for the gauge to hit 80. And I ran my VIN by the parts guy at the Mercedes dealership, and he told me it'd be the 119 style. But I suppose if it's an item that needs replaced somewhat regularly, it'd probably be best just to replace it. And it sounds like I should do a full coolant flush?

 

[ollo]

Got my 94 E420 in April with 229K and records didn't show thermostat was ever changed. The temp would settle below 80C on cold mornings but my heater also worked fine. When Summer heat came, it would flirt with 100C in traffic on the hottest days which looked like classic stuck thermostat symptoms to me. I replaced it with a Wahl oem from Autohaus and immediately the temp gauge would come right up to sit at the upper edge of 80C on cold mornings and on hot days(90-100F) it never went above 90C, so problem solved. My 94 had the early type thermostat. Don

 

[srdavis872]

Sounds just like mine. So you think I should ignore what the parts guy said and get the early style one? Mines a 94 that was built in 08/93, but I gave him my vin and asked which style it used, and he checked and said 119.

 

[Klink]

Sounds just like mine. So you think I should ignore what the parts guy said and get the early style one? Mines a 94 that was built in 08/93, but I gave him my vin and asked which style it used, and he checked and said 119.

You will not have a "choice" over which thermostat to use. It depends on which water pump is installed on your engine.

Pay some extra attention to the photographs that Dave posted just up above. Note that the early version thermostat in the picture is the working component of a thermostat assembly. On the early version, those thermostat "guts" will be installed in a tapered, slightly bowl shaped housing that exists as a separate part not rigidly connected to the internal thermostat components.

Note that the late version thermostat is an integrated assembly where the working components of the thermostat and it's outer housing are combined into one assembly. The difference is easily seen as the visible outer housing of the late version is a flat plate.

Here I have posted a couple of photos of the early version as installed on an engine. Note the slightly rounded profile of the early version housing as opposed to the flat plate on the late version thermostat assembly.


Take those photos from Dave's post above, and these photos and look at your engine. Note that the thermostat is mounted in the passenger side of the water pump. If you see a flat plate like the one pictured on the right in Dave's photos then you have the late "119" version. If you have the rounded housing shown in my pictures, then you have the early "116" version.

The early version is shown in these two photos.

 

[srdavis872]

Well, from what it looks like, the dealership was wrong. Glad I posted something because I was this close to buying the wrong part this morning.

 

[gerryvz]

They don't call them "stealerships" for nothin' .... glad that this forum saved you some time, money and hassle.

 

[gsxr]

Dealer parts guys usually make the mistake of seeing the 116- prefix on the "early" t-stat part number, and thinking it isn't correct for the M119 engine.

They SHOULD ask for your VIN, which would confirm which part is needed.

 

[srdavis872]

Dealer parts guys usually make the mistake of seeing the 116- prefix on the "early" t-stat part number, and thinking it isn't correct for the M119 engine.

They SHOULD ask for your VIN, which would confirm which part is needed.

They did ask for my VIN and printed out a quote sheet with the 119 part number on it. I first said "I know these have 2 different styles, can you tell me which one I should get?" but this was before today when I knew there was a visual difference on the outside. So, not really sure what happened...

 

[gsxr]

They did ask for my VIN and printed out a quote sheet with the 119 part number on it. I first said "I know these have 2 different styles, can you tell me which one I should get?" but this was before today when I knew there was a visual difference on the outside. So, not really sure what happened...

Ah, so they really didn't do their homework, did they. OR, they do not know how to use the EPC! There are footnotes in the EPC, they are supposed to read those... early t-stat is used through engine 119.975 serial #20,771.

 

[Klink]

They don't call them "stealerships" for nothin' .... glad that this forum saved you some time, money and hassle.

LOL, Jet Lag got you cranky? Wake up and smell the cork! That was more of a stupidshit than a stealership thing.

Note that it was also a soiled evildoer in the fetid bowels of a "stealership" that did post number 6 so that he could just pick it out for himself. Not that he should have to, but I think it is also possible that he could have had either water pump installed on that engine at some point in time. I think either version pump will fit on his engine. And no, I'm not saying that his parts specifier knew or thought of that, I just thought that the possibility existed, so that's why I thought some extra effort was appropriate just in case something like that was in question here...

 

[gerryvz]

I've seemingly got a lazy thermostat in my E500 .. more and more convinced of it. It's taking a fair bit longer than it used to to warm up -- i.e. the temp gauge is staying below the 80C mark for a number of miles. Eventually it does pop up to the 90-100C mark. Today we had 72F temps outside, and while out running errands with my wife the hottest temp I saw was a straight-up 90-92C in traffic. If it was summertime, it'd be a full-on 10-12C higher temp.

Just pulled my spare thermostat out of my parts stock. I've had it for several years -- a Behr OEM part 116 200 03 15. I had originally purchased this as a spare for my 560SEC, but it also works perfectly for the M119 up to engine serial #010204 (500E/E500) and #020771 (400E/E420). Given that my motor was produced in later 1993 as a 1994 model (engine #008486) it's safe to say that it (like most all US E500s and ALL US 500Es) uses the "early" style thermostat.

Looks like another HOW-TO is on the way in the near future.....

Price for the Behr is around $25 at AutohauZ, and nearly double that for an OE MB thermostat (dealer is in the mid-$80 range for MSRP). You can also get Wahler thermostats via AHAZ for around $30 a pop. DO NOT get the Meyle aftermarket units.

Just as an FYI - this thermostat was ONLY used for the early series M119 engines as mentioned above (also the CIS-E-injected M119.960 series), the 4.2-liter M116 engines, and the iron-block 4.5L and aluminum-block 5.0L and 5.6L M117 engines.

M104 motors use a different thermostat.

Cheers,
Gerry

 

[jhodg5ck]

Get the wahler..better built then behr IMHO.

Jono

 

[gsxr]

OE is Behr for the early 116- stat... the later OE 119- stat is Wahler. Pics below. The Wahler version is visibly different for the 116- version. I had been sticking with OE/dealer stats until the recent price hike ($64 list).

http://www.w124performance.com/images/M119/thermostats/

 

[Klink]

OE is Behr for the early 116- stat... the later OE 119- stat is Wahler. Pics below. The Wahler version is visibly different for the 116- version. I had been sticking with OE/dealer stats until the recent price hike ($64 list).

http://www.w124performance.com/images/M119/thermostats/

I am not positive about this, but I think the early version thermostat was available from both Behr and Wahler, and I think that is what Jono was referring to. I don't think he was implying that you could interchange the early and late versions, which clearly cannot be done.

 

[gerryvz]

Yes, the early ("116") thermostat is definitely available from Behr and Wahler.

GSXR was correct - although of a similar design, the Behr and Wahler design details are visibly different.

And BOTH are extremely different from the integrated OEM Wahler "thermostat+housing" for the late M119s.

Cheers,
Gerry

Behr:



Wahler:



Later M119 thermostat (with integrated housing design), Wahler:

 

[gsxr]

Yes - Klink and Gerry both read my mind correctly.

What I meant was the OE dealer t-stat is made by Behr, not Wahler. You can get an aftermarket Wahler/early t-stat. There is enough visible difference that I was nervous about using the non-OE item, but I'm probably just paranoid.

 

[Klink]

Actually, speaking about the early version / 116 part number, I prefer the Behr. Notice that the Wahler is assembled by peening at the pin retainer bail. I have seen a number of thermostats of this design break at the peen. In almost all cases, it involved the "110" part number thermostat that is used in countless six and four cylinder engines, most notably to our frequent discussions, in the 103 and 104 engines. Admittedly, I have never seen that type of failure of these thermostats in the V8 engines, but I have seen enough of them fail in that manner in other engines that I am not crazy about that particular design. Do note however that I do not consider them "dangerous". In every case that I have seen that type of failure, the engine was too slow to warm up, and/or ran too cold. Though I have not seen it anywhere in print, it is my belief that failures of this type led to the design of the hyper-strong second version construction...

 

[clarkz71]

Yes - Klink and Gerry both read my mind correctly.

What I meant was the OE dealer t-stat is made by Behr, not Wahler. You can get an aftermarket Wahler/early t-stat. There is enough visible difference that I was nervous about using the non-OE item, but I'm probably just paranoid.

Dave is correct. I also recommend Behr.

Wahler is inconsistant with temp control
I had one and my gauge ran 85 to 90
in normal conditions.

Switch'd to OE Behr and dead on 80c

I have a new Wahler on my desk.

Free to anyone, just pay shipping.

 

[jhodg5ck]

Idk...work solid for me, sans issues after 10 + years

 

[clarkz71]

It's also build quality.

The bridge is attached weakly on the Wahler. I've seen those separate

Much more solid contruction the Behr.

Behr.................................................................Wahler

 

[Klink]

Thanks Clark! Your photos show exactly the failure area I was talking about in post #19.

 

[Glen]

I had an M104 Wahler fail exactly as you described Klink. I thought it was a fluke, I guess not.

 

[clarkz71]

Thanks Clark! Your photos show exactly the failure area I was talking about in post #19.

I had an M104 Wahler fail exactly as you described Klink. I thought it was a fluke, I guess not.

You're correct Glen,no fluke.
I've seen it twice on a Benz, and that design thermostat on several other model cars.


.

 

[gsxr]

Yikes! I didn't know about the possible failure. Some other (non-M119) OE 'stats are similar to the Wahler shown above (the OM60x, IIRC?). I'll have to keep an eye out in the future. Thanks for the info, everyone!

 

[Klink]

Yikes! I didn't know about the possible failure. Some other (non-M119) OE 'stats are similar to the Wahler shown above (the OM60x, IIRC?). I'll have to keep an eye out in the future. Thanks for the info, everyone!

In fairness, like I said above, I had seen that particular failure only on the "110" version Wahler thermostat. Note that the 110 version thermostat is 87°C opening temperature, and in all of its installations it is in the hot coolant/outlet side of the system side of the system, while almost all of the other thermostat installations on mid '70s and newer MB engines are in the cold water/inlet side. Possibly the additional thermal stress of the 110 installation contributes to the failure.

I would never remove a thermostat to "inspect" and replace it if it was not my preferred version. I am simply saying that if I was replacing my thermostat for whatever reason, and I had the choice of which construction to use, and that choice version was conveniently and expeditiously available at a reasonable price, I would choose the Behr style construction.

 

[clarkz71]

For me it's simple. Behr is what the car came with
and what the dealer sells

Besides what I already mentioned.

On the late 119 you have no choice.
Only Wahler manufactures those and is OE.

 

[gerryvz]

Dave .. I think your Stigwagen has a Wahler 110 (87C) 'stat in there.....

 

[Klink]

Dave .. I think your Stigwagen has a Wahler 110 (87C) 'stat in there.....

What would Kent say about that?

Fortunately, in that installation it is extremely easy to inspect and/or replace, because you know he's going to do that now...

 

[gerryvz]

104 & 119 stat replacements are much nicer than 117s..........


Sent from my iPhone using Tapatalk

 

[Klink]

104 & 119 stat replacements are much nicer than 117s..........

Well, they certainly don't get any easier than on the M104...

 

[clarkz71]

Autohaus AZ claims Wahler is OE......... hmmmm

I would order one from Lionel to find out, but that would be $45. Almost double from AZ

MSRP is $64. WTF????

 

[Klink]

Autohaus AZ claims Wahler is OE......... hmmmm

I would order one from Lionel to find out, but that would be $45. Almost double from AZ

MSRP is $64. WTF????

If you are talking about the 110 part number version for the M104 engine, I am not surprised. I have seen both the Behr and the Wahler come out of MB boxes at the dealer. I have not noticed if the same thing is true with the 116 part number thermostat for the M119 engine, because we have replaced so few of them, while replacement of the 110 version thermostat in all of its various installations is a daily occurrence. And yes, it is because most of them are broken at the assembly crimp point that you illustrated with your photographs.

 

[gerryvz]

Note that the 110 version thermostat is 87°C opening temperature, and in all of its installations it is in the hot coolant/outlet side of the system side of the system, while almost all of the other thermostat installations on mid '70s and newer MB engines are in the cold water/inlet side.

Klink, can you talk about why MB would have placed the thermostats for these engines in different locations in the cooling circuit?

What would have dictated doing this? Are there advantages/disadvantages to having the thermostat placed in the hot/outlet side of the cooling circuit, as opposed to the cool/inlet side?

Cheers,
Gerry

 

[Klink]

I don't know why they do alternate placements. My experience over the years has been that the engines having the t-stat in the cold water inlet seem to have more stable temperature regulation in various conditions. This was especially noticcble when they moved the 615/616/617 t-stats to the cold water side.

 

[gerryvz]

I have become convinced over the past year or two that the quality of Behr (Mahle) thermostats has gone downhill. I have installed Behr units on my G-wagen (in 2014, and replaced again in early 2019), and my E500 (in early 2015), and both of them in my opinion have been faulty and have gone bad somewhat prematurely.

The G-wagen unit was OK for a few years, but starting in late 2017 I started having massive cooling temperature problems with that engine. After replacing a new factory fan clutch with a second new one, and the original radiator with a Nissens unit, the cooling problem was solved with a replacement thermostat. I mean, DEFINITIVELY solved. I can't get the truck's M104 past 95-100C even on the very hottest day with the A/C blasting. It used to "love" temps of 110-115C.

This Behr thermostat had 30,000 miles on it.

The E500 is another situation. I had replaced the thermostat with a Behr unit back in early 2015, when I was living in Texas. For the past 18-24 months, I've been noticing that the E500 is taking an inordinate amount of time for the coolant temp needle to get over the 80C mark to the normal ~90C level. It stalls out at around 70-75C for a LONG time after the car is run, and then after 10-15 miles will finally "break through" to the ~90C level, indicated.

In the more temperate times of the year, here in Maryland, the temp stays at the 90-95C level, which is where it should. In the hot season (i.e. ambient temps at 70F and higher), it tends to climb up to the 105-110C level on the hottest days. The fan clutch is a low-miles clutch that was removed from a 500E with 50K miles on it (when removed), and the radiator is a replacement Nissens unit that I installed when I lived in Texas (in July, 2013). I have a brand-new replacement factory Horton fan clutch that I have not installed on the E500.

I believe that given the behavior of the coolant temp reaching an indicated proper operating temperature, that the thermostat is bad.

This E500 Behr thermostat has less than 14,000 miles on it.

I replaced the thermostat on my 560SEC (which uses the identical thermostat as the E500E / M119), back in late 2017, with a Behr unit. The previous thermostat had been installed for 8 years and 61,000 miles, and had also started being lazy when it came to warmup and indicated coolant temps in colder weather. The new thermostat also immediately solved the "lazy" warmup situation.

From now on I am going to buy Wahler thermostats for my vehicles and see if the quality is better on them, and if they last longer. I believe that Behr thermostat quality has suffered.

 

[gsxr]

I've been generally recommending t-stat replacement at 5 years, same time the G-05 coolant should be flushed & replaced. The t-stat should last more like 10 years but it's relatively cheap insurance to change proactively.

I haven't used a Wahler early (116- p/n) unit so I can't comment on that vs OEM Behr.

 

[gerryvz]

I think 8 years and 60K miles on a thermostat is plenty of life, and I was satisfied at that. But 30K and <14K miles on the other ones is IMHO premature failure, and unacceptable.

I am noticing that Wahler thermostats are significantly more (on the aftermarket) than Behr units. I am not sure whether that is a function of where they are made, overall quality, or what. Of course Febi thermostats are sitting at around $10 apiece, or less than half the cost of a Wahler.

 

[gsxr]

Where are you seeing the Wahler costing significantly more? It's only twenny-five cents more at RME:

- Parts Search

www.rmeuropean.com

 

[gerryvz]

Where are you seeing the Wahler costing significantly more? It's only twenny-five cents more at RME:

- Parts Search

www.rmeuropean.com

Search for '1162000315' | FCP Euro

parts online. Buy OEM & Genuine parts with a Lifetime Warranty, Free Shipping and Unlimited 365 Day Returns.

www.fcpeuro.com

https://www.autohausaz.com/catalog/c/mercedes/1994/1195635-e500/16-cooling_system/2200-thermostat?s=d&page=1

 

[gsxr]

Well, I guess you could buy from one of the places that charge more.

C'mon, try the Febi as a science experiment!

 

[Ivogeorge]

Hi Gerry, would you mind confirming that thermostat OEM 116 200 03 15 fits the housing 119 203 00 74?
Mine is '91 500E European model, the "experts" at the local Mercedes dealership sold me the Original thermostat 119 20 00 15 which doesn't fit.
Thanks

 

[gerryvz]

I would need your VIN or engine number to definitively confirm that, but as mentioned on this thread, there are only two types of thermostats that were fitted from the factory, to the M119 as used in the E500E.

First type -- removable thermostat from separate housing. Used up to engine #10204.
Second type -- integrated one-piece thermostat and housing. Used from engine #10205.

The first type, which is used with the removable thermostat housing as shown in your second photo above, is used on all but the VERY LAST E500s. To the best of my knowledge, all 1991, all 1992, all 1993, and about 95% of 1994/1995 models used the "early" removable thermostat. The first type of thermostat is indeed part number 116 200 03 15.

It is possible to retrofit the second type of integrated thermostat onto the water pump, but you cannot use the separate housing if you do. The part number for this second type of integrated thermostat is 119 200 00 15.

My recommendation is just to get the early type, and keep your separate housing. Return the integrated one. But you can use either one ... it is your choice.

I have seen other situations where people have had mechanics "substitute" the later style thermostat onto a car that was originally equipped with an earlier one, including a couple of people on this site. It's not an uncommon substitution and is probably because some mechanic just went with what a parts catalog said.

Here is the MB parts catalog, showing both.

 

[Ivogeorge]

Thank you very much! Will do as suggested. Cheers

 

[Ivogeorge]

forgot to send the chassis number: WDB 1240361B471776

 

[nocfn]

there is an earlier post showing the Behr and Wahler units for the late style tstat. The wahler versions I have are all of similar contruction of Behr. I belive the manufacture change was warranted and all 4 in my parts stash are Wahler and are of the same new style robust construction.


The black sharpie marks are where I will drill small holes thru to all for better seapage while the Tstat is closed. (not for climates that are less than the Gulf coast humidity) YMMV