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190E, SLK350
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Discussion Starter #1
I have pretty much tried everything without success.
Issue: Coolant leak from upper radiator hose at the thermostat housing
Action:
Replaced the hose
Replaced several clamps (some failed from over tightening)
Replaced the upper thermostat housing(The plastic top with reinforcement)
Replaced the thermostat seal

Observations:
After I let the car cool, coolant starts seeping out the hose where it meets the thermostat housing.
I put my ear to the hose and squeezed, I can hear air squeezing out. In other words, no matter how tight the clamp is, something is escaping from the hose where it meets the housing neck.

Please give me a focused solution and try not to go all ADD. This is not the Stalling Again thread :(
 

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1993 190e-2.3
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765 Posts
Try a better brand of hose. I went thru this with the top radiator connection. I think I had trouble with URO hoses.
 

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Outstanding Contributor
'85 300D Turbo, '91 420SEL, '92 190E 2.6, '09 C350, '12 E63 Wagon
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3,164 Posts
Try a Gates Power Grip Clamp.
 

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'01 SLK230,'93 190E 2.3, 1971 LS5 Corvette Convertible
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2,193 Posts
I have pretty much tried everything without success.
Issue: Coolant leak from upper radiator hose at the thermostat housing
Action:
Replaced the hose
Replaced several clamps (some failed from over tightening)
Replaced the upper thermostat housing(The plastic top with reinforcement)
Replaced the thermostat seal

Observations:
After I let the car cool, coolant starts seeping out the hose where it meets the thermostat housing.
I put my ear to the hose and squeezed, I can hear air squeezing out. In other words, no matter how tight the clamp is, something is escaping from the hose where it meets the housing neck.

Please give me a focused solution and try not to go all ADD. This is not the Stalling Again thread :(
Hey Drew, wasn't there a recall to replace the plastic thermostat housings with metal ones? My '93 has the metal housing with a rubber o-ring.
 

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93 190E 2.3, 94 E320 (sold), 01 E320, 99 S320, 18 Durango
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Drew, I had the same issue like yours when I had to replace a bad upper hose. My 93 2.3 came originally with the black plastic housing. I had to go through couple plastic housing and hoses replacement till I bought a used metal housing on ebay that fixed the issue.
 

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190E, SLK350
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Discussion Starter #7
Drew, I had the same issue like yours when I had to replace a bad upper hose. My 93 2.3 came originally with the black plastic housing. I had to go through couple plastic housing and hoses replacement till I bought a used metal housing on ebay that fixed the issue.
What about the piece that threads on top of the housing for the tank return? Do they sell that as well?
 

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190E, SLK350
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Discussion Starter #9
Hey Drew, wasn't there a recall to replace the plastic thermostat housings with metal ones? My '93 has the metal housing with a rubber o-ring.
Mine is a 88 I don't think Mercedes would honor a recall on my car.
 

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190E, SLK350
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Discussion Starter #10
Try a better brand of hose. I went thru this with the top radiator connection. I think I had trouble with URO hoses.
URO is trash, I could never buy from them after being burnt a few times.
This hose is OEM.
My original hose was leaking the same way.
 

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93 190E 2.3, 94 E320 (sold), 01 E320, 99 S320, 18 Durango
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Mine is a 88 I don't think Mercedes would honor a recall on my car.
I was just suggesting that you might want to replace the plastic housing with a metal one. When I took my '93 in for the first free service, they replaced the housing.
 

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93 190E 2.3, 94 E320 (sold), 01 E320, 99 S320, 18 Durango
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I was just suggesting that you might want to replace the plastic housing with a metal one. When I took my '93 in for the first free service, they replaced the housing.
My 190 was always dealer maintained in the first few years but they never replaced the housing cover and it had the black plastic one till I replaced it with a used metal one myself.
 

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'01 SLK230,'93 190E 2.3, 1971 LS5 Corvette Convertible
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I was just suggesting that you might want to replace the plastic housing with a metal one. When I took my '93 in for the first free service, they replaced the housing.
My 190 was always dealer maintained in the first few years but they never replaced the housing cover and it had the black plastic one till I replaced it with a used metal one myself.
I'm not a big fan of the dealers, but the one in Tampa was pretty good about staying on top of Service Bulletins.
 

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190E, SLK350
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Discussion Starter #15
I am puzzled. My previous plastic thermostat upper housing never leaked until after I replaced the water pump. Why would a new thermostat plastic housing leak right off the box as well?
Anyway, the metal housing could be my next step but that banjo nipple is outlandishly expensive relative to the other parts, that is if I can find it.
I have a feeling that I am chasing a pressure problem rather than a fit.
 

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89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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Don't mean to insult anyone but have you checked the radiator cap?
I suppose it could be not releasing the pressure when needed.
 

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190E, SLK350
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Discussion Starter #18
Don't mean to insult anyone but have you checked the radiator cap?
I suppose it could be not releasing the pressure when needed.
It's a fairly new one. I replaced it last summer after I replaced the water pump.
I could test with the old one, if I can find it. There was nothing wrong with the old one... I think. I will have to look.
 

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190E, SLK350
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Discussion Starter #19
Plastic thermal expansion varies, but seems at least double that of aluminum or steel. Maybe the expansion rate on the new one is on the higher side of the broad range. I believe you need a non-metal clamp.

Coefficients of Linear Thermal Expansion
I can't find a source for some good clamps for this application. So far, I have ruined a couple of them from over tightening (Pep Boys sourced)
 

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'85 300D Turbo, '91 420SEL, '92 190E 2.6, '09 C350, '12 E63 Wagon
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I can't find a source for some good clamps for this application. So far, I have ruined a couple of them from over tightening (Pep Boys sourced)
I had a really hard time, injuring my hands trying to get the Power Grip Clamp with hose for the upper radiator hose on the 2.6L. I measured the diameter of the hose very carefully, but the "nipple" on the housing was just over the diameter of the clamp I bet. I backed it down the hose a little and was able to force it on with a lot of effort! The lower clamp was loose and (I secretly used my wife's hair dryer to shrink it some. Instructions say to use a heat gun, which I have, but in past experience it is too hot to control in whatever I was trying it on.) Not a single drop of coolant came out of either end. (I didn't expect any to drip out the tight upper connection, but the lower one I wasn't sure because it was hard to get heat onto it. The clamps are designed to increase clamp force/shrink with the heat of the hot coolant. Worked great, until the car stalled and would not start maybe 5 to 10 minutes later. (It seemed to shrink the area after the "nipple" a little more than I would want, but not that bad.)

I'm amazed you could break a metal clamp on a plastic "pipe", if I'm understanding the problem correctly. Those are terrible. The reason I switched to this type was that after 25 years there are clamps that are no longer good. I tighten them, and then later they are loose, and leak! They are quite expensive though at around $5.xx they are probably the most expensive clamps around, available at O'Reilly's. I had some sort of discount code at the time...

I'll try to take a pic... BRB
 
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