Seeking comments on M103 water pump and belt tensioner longevity
 

Background: I special ordered my '88 red/palomino 190E 2.6 five speed in August '87 and took delivery exactly 36 years ago in February, 1988. It had a lot of problems, but I really liked the car (and still do) and wanted to get it right, and the dealer was very good at fixing all the problems.

The four year/50K end of warranty hit at about the same time, and just before the head gasket and water pump had to be replaced, and they went ahead and refreshed the head with new valve guides and the latest (Viton) valve guide seals to address higher than normal oil consumption. I also had them put it together with a new accessory drive belt.

So now 32 years later it has about 87K miles, an average just short of 1200 miles per year, and I'm now down to no more than about 500 per year.

I've been concerned about that 32 year old drive belt and that silly "rubber donut" belt tensioner. A friend bought an automatic about the same time as me, drove it about 80K miles over the next four year and had that belt tensioner rubber donut fail causing the belt to break, which took out the trans cooler hoses making a big mess in the engine compartment destroying the hood pad. I think the bill was on him as it was out of warranty.

About ten years ago an acquaintance asked me to help him change the belt tensioner on his 300E, and I agreed if he would buy the special tool needed to remove the fan assembly, which he did. So I did the job and he agreed to loan the tool to me for when I did the job on my car, but unfortunately he passed away about five years ago, so no tool.

At this point in my life the job is probably too much for me, anyway, so I'm talking to Mercedes and BMW specialists A & R German Motors, a small shop in Hermosa Beach, CA, about two miles away from me about doing the job. They replaced the center drive shaft bearing ten years ago, which had also been replaced by the dealer during the warranty period.

In addition to preemptively replacing the belt tensioner and belt before they fail, the clutch fan is dead and needs to be replaced, and I'm debating whether or not to preemptively replace the water pump. I'm going to talk to Ralph (the MB specialist) about me buying the parts to take advantage of Pelican's new lifetime warranty on most parts. I'm also concerned about what brand to buy, and there are considerable differences in price on some parts. Here are recent Pelican prices on the major parts I will need.

Belt tensioner
.....MB $251.84
.....Febi $129.00
.....URO $87.00
Damper
.....Stabilis $29.29
Belt
.....MB $52.09
.....Continental $29.75
Fan clutch:
.....Meyle 83.75
.....Behr 140.75
.....Febi ????
Water Pump:
.....Laso $132.00
.....Graf 119.50

I'm not sure about replacing the water pump. Will it last another, maybe, ten years and no more than 5000 miles? The price of the pump is probably small compared to the labor if it needs to be replaced, but how good are the Laso and Graf pumps!

Any and all input is appreciated.

Duke

The water pump on the M103 and early m104 is the worst and most frustrated job you can do on these engines. Mercedes started with the water pump and build the car around it. If you can find one, get a mercedes water pump and make sure to order the small hose from the pump to the block as well. Another marvel of engineering..

On my 300SE M103 I did it while the head was off, with the 300CE M104 I wasn't that lucky. Took me a week of frustration, it's just luck when you hit the bolts to fasten them. At most m103 or m104's you will find the back/hidden bolt loose, most mechanics will give up.

Since the usage is approximately 500 miles per year I wouldn't do preemptive repairs unless I suspected something was starting to fail.

I would definitely replace the bad fan clutch with the Behr.

If choosing to do the belt it will need a tensioner soon after as old tensioners aren't happy once they are disturbed. If doing the belt and tensioner, replace the bearing bracket and the two small pulleys, one is grooved one is smooth. Febi should be fine for these. Spin the alternator and the AC compressor clutch by hand and listen for noise/condition, both have replaceable bearings.

Water pump brand, try to get a MBZ remanufactured pump, the old one is needed as a core.

As a recap, I'd do only the fan clutch now with the Behr but go farther if something else was presenting a symptom of future failure.

Belt tensioner
.....MB $251.84
.....Febi $129.00
.....URO $87.00: Tensioner 103 200 0870 or Tensioner w/ Hardware 102 200 6970

I like your description. Mercs of that era were very well engineered, but I often question the complexity of some designs. The most elegant solution is usually the simplest that does the job, and its usually the least expensive.

Consider the M103 throttle linkage. My '63 Corvette has three basic fabricated pieces (no cable) from the carburetor throttle lever to the throttle pedal... very simple, reliable, and low cost.

BTW, that M103 throttle linkage design had a serious flaw that resulted in a recall of models that use it, EXCEPT the 190E 2.6. I chronicled my experience with this issue in the following thread about ten years ago.

http://www.peachparts.com/shopforum/tech-help/354593-m103-owners-check-throttle-linkage-plastic-retainer-2.html

Duke

Thanks for your response. I plan on driving down to A and R German motors tomorrow morning to talk to Ralph and probably make an appointment to get the work done. I'll let you know.

Duke

Removing the lower bold is very easy with a Snapon FLXM13.

I used a bended rod and an Allen key socket welded to a steel strip to remove the fan clutch.

Rob

Some cars used one hex/allen bolt and 3 regular hex head bolts. The FLXM13 and a snap on 1/4" drive flex/universal with a very short 5?mm hex bit was the ticket.

If it was an M103 in a 190E 2.6 THAT was a headache...

I screwed myself when I replaced the fan clutch two years ago, loosened it with an allen/hex, but the bold was a torx, stripping it instantly. Took me a couple days to get it out without damaging anything.

Do this when you replace the tensioner: It seems the tensioner is the weak link when anything is done involving the belt. This way even if the tensioner fails, you will always have adequate tension on the belt without slippage or overheating. As far as everything else goes, I don't understand what the issue is, just replace the parts with OE or OEM (not necessarily MB branded from dealership). It shouldn't be that big of a decision since you are dealing with either critical parts or parts that if they fail the job won't necessarily be a 5 min job especially if you aren't doing the work yourself.

Smart.

Ralph wasn't able to get back to me with the estimate and parts choices, but I should hear from him next week. I have an appointment to take the car in on March 5, and he should have all the parts by then.

Regarding the MB "rubber donut" belt tensioner I'll offer the following observations. In 1988 I won the sedan, under 3-liter class in the Silver State Classic challenge (128 MPH average, 132 top radar recorded speed along the course) a 97 mile course over Nevada State Route 318 from Lund to Hiku in the northeast part of the state.

My navigator, one of my IBM associates got so excited about open road racing that he bought an '89 Saleen Mustang that I prepared and drove while he navigated again in the '89 race. We should have averaged over 150, but we got rained on early in the morning and the first third of the course was still wet. At 130 the front began to feel a little light, so I held that speed until it dried out. Then we quickly got up to 150 and slowly gained speed with a radar gun recorded 159, but only averaged 140 for the entire course due to the restricted speed early on.

Part of the prep I did to coax a bit more power out the 302 HO Ford engine was install an underdrive pulley to the crank, which required a slightly shorter drive belt. The tensioner was basically a torsion spring with a pulley and tension can be relieved with a socket on a 3/8" breaker bar, so changing the belt was about a one minute job. I had the same experience with a C5 Corvette.

Like I said before, these vintage Mercs are very well engineered, but do they have to be so bloody complicated?

I like the helper spring on the damper. Can you tell us a brand/part number and where to buy? Great idea, but how did you get the spring installed over the eye?

Duke

I can't remember exactly where I got the spring from, just as long is it has a decent compression rate and will fit around the damper. As for the shock and tensioner, I don't remember, I think the shock could be Sachs. The tensioner is Uro brand that I just replaced in December 2023 . If you go with Uro brand, make sure you do this mod otherwise you will be replacing it again in a year or so. The tensioner is actually a warranty replacement from a previously failed Uro tensioner after about 2.5 years. However, doing this mod, it won't really matter if the tensioner fails because the spring will be holding the tension on the belt. This may actually extend the life of the tensioner itself. I opened one of these tensioners up and found that it's nothing more than a giant rubber bushing. The torquing of the tensioner is nothing more than the rubber inside being twisted and wanting to spring back to it's original mold is what provides the tension. No idea why MB wouldn't just use a large spring for this.

Which is why I installed the late 94/95 W124 M104 AC and power steering bracket, allowed the use of the updated style tensioner. Much much better and easier to service. Wish there was an underdrive pulley available for the crank or overdrive pulley available for the fan as slipping the belt between the two is a pain to do.

Does anyone know of an "upgraded" M103 belt tensioner that is a bolt-on using a steel torsion spring rather than the Mickey Mouse "rubber donut".

Elastomers like rubber exhibit a phenomenon called "creep" if under load for a long period causing them to "relax," and if unloaded will not return to their original shape. For this reason only a moron would use rubber as a tensioning device.

Most metals like iron (and its steel alloys) and aluminum alloys have insignificant creep characteristics if loaded below their yield limits. That's why the Brooklyn Bridge is still standing. If it was made of rubber its would have collapsed at least a hundred or more years ago.

Duke

There is no "upgraded" tensioner for the M103 nor will there ever be one unless you are able to build one yourself. I thought about it when I took the one I had apart, but then I just scrapped the idea. The sad reality is that we are the last of a dying breed. I don't know of anyone that was born in 2000 or after that would bother with half the stuff anyone on this forum does. I was at a gas station about 6 months ago with a coolant leak and asked the guy (maybe in his mid 20s) if he could turn on the water. He had zero idea that the air machine also has a water feature nor did he understand why I would put water in my car. He also asked several of the other workers and one girl said she didn't know and thought it was "weird" that a car needed water. Funny thing is, I'm probably not even old enough to be their parents (well some of them I could be) and they all had ZERO idea! Interesting enough I see articles like the one I attached of a 2014 Tesla reaching 1.2 million miles after going through 14 motors and 3 battery packs and seems like everyone is amazed lol. And Here I am in my W201 with 580,000 miles and only 1 engine upgrade to the 3.0L at 531,000 miles. :icon_rolleyes:

Wow, only about 87K miles per motor. Where I live Teslas are the "yuppie staff car", and they all look the same. Did you read about the Swedish guy who blew up his Tesla with several pounds of dynamic when he found out how much a battery replacement job cost? I really liked that story!

BTW, if you got 531K miles out of the original 2.6L I-6 how many times did you refresh the head or do a complete engine rebuild and have to replace the cam belt tensioner, water pump, and center driveshaft bearing or other significant parts you can recall?

If you outlive me maybe you should buy my 190E 2.6 from my estate. I assume you're old enough to know how to drive a "stick shift". ;)

Duke

I keep a log of what was replaced, when it was replaced, and how many miles is on the odometer when it was replaced. I've owned the car since '05 so nearly 20 years, so I have done pretty much only normal wear items. I did have the transmission replaced in 2013 with a used one and also in 2021 with another used one, both times the reverse was gone. That is the only major repair/replacement I had to do. A/C compressor, water pump, alternator, tensioner were replaced a few times. PS pump was resealed twice, steering gear box resealed twice. Center bearing on driveshaft replaced a few times (Uro parts premature failure). Replaced a rear axle with a good used one, courtesy of W123fanman, because I ended up stripping the end threads on the axle nut end. Pretty much all rubber has been replaced at some point or another, but other than the valve stem seals, I never had to open up the engine at all. The only reason I had to replace it was because a connecting rod bearing was worn due to low oil from a failed dash light. By the time I did the troubleshooting, the oil pressure had already been declining. So instead of fixing it, which would require the engine removal anyways, I just let it go and drove it until it gave up on me.....long stretch of highway doing about 75 in a rural area. I heard the rod knocking sound change and then I decelerated because I knew something bad had happened and then car temp started going up as I was pulling over and I saw steam. When I popped up the hood I could see coolant pouring out of a hole in the freeze plug. Something had went through it and made a small hole in it. That was it. I already had the 3.0L on standby at home. I have 1 other 3.0L and two 2.6L as well. So I can resurrect this car another 2-3 times if I need to. :D;)

Your dedication to your car is inspiring, I'm glad to have been able to get you that axle, though I found a few months back I needed to do both on my 260k mile Sportline haha. I'm currently swapping in a M104.981 into that car and doing a bunch of maintenance at the same time. The 3.0L that was in it was fine but I had to pull it to do some transmission work and found that engine for cheap at an old rural yard that didn't ever have anyone looking at the Mercedes in their acreage.

Here's how I did mine:

94-95 E320 ac compressor/power steering bracket, part number is A1042300142

W124 AC compressor to fit that bracket (most M103 and any M104 W124s used it). Denso part number is 471-1224, though it has been discontinued.

Belt tensioner part number A1042000870 and three attachment bolts N910143008003

Pulley I used was A1192001470 but there's also A1042001070. Attachment nut is A1119900053.

Belt is dependent on a ton of factors, I'd just measure for fitment.

The 190E AC lines will still work but they are pushed back slightly. You have to remove the front intake support bracket. I used some random bracket I had laying around to add extra support to the fuel cooler assembly on the hose.

Not an easy or fun job but gives you the modern belt tensioner.

We passed your posts and photo along to our Engineering department. They probably won't go for the spring mod, but it'll get them thinking about the rubber donut issue. Thanks!