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How to replace "Bypass Hose" for 1990 300 SEL
Is this a big job?
My bypass hose has a leak. I can't just replace the hose, it looks like I have to take somethings off such as the thermostat or the water pump. Does anyone know what I need to do? I have no idea why Mercedes engineers made this so difficult. Thanks, Matt |
You need to remove the waterpump to replace this hose.
Not a simple job but is doable - it's just time consuming and you need to have all the correct tools. There is a DIY on this in the resources section under DIY articles. |
Been there done, that. It's not hard just time consuming. May as well replace the water pump while in there, any other hoses, new belt, and flush the system.
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thank you.
This may sounds like a dum question though, what would be the harm to taking a hacksaw and cutting a 1/2 inch off the pipe that connects to the block? This would allow me replace the hose in 2 minutes. Is there any reason why the bypass hose has to be so short? Any reason why the thermostat is so close to that pipe? My hunch tells me that the reason why it is so close is because of the pressure from.the water pump may cause a leak if not so close. |
I doubt it generates enough pressure to rupture a hose. Its probably designed that close because the German engineers like to have metal between connections more than rubber. :D I'd leave it alone and repair it correctly. Hacksaw = metal particles into cooling system, not good.
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Don't know, let us know how it turns out. :D |
Thanks.
My other thought that this is how mercedes gets people to go to the dealership for repair$. |
Well, it's bound to happen sometime...
Just about everyone here isn't the first, second, or even third owner of their cars. So knowing what has been done and what hasn't is an issue. You could be on your second one and second water pump. That's pretty good for over 300K................. |
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AS the vehicle is nearly twenty years old, you should replace water pump, thermostat, tensioner, belts and hoses. (flush radiator) |
I replaced it...
without removing the water pump in my 300e. Yes, I cut the hose and installed the new one through the gap. The secret is buying the hose from the dealer as it is more flexible than after market. You will need lubrication and a lot of patience but, it will get in there. Worse comes to worse, you will need to remove the water pump. By the way, if you need to cut the pipe, make sure it is on the water pump side.:D
Good luck! |
thanks.
by the way, why on the pump side? i was thinking of cutting the pipe on the block side. seems long enough. |
i second the line on replacing the water pump.....as you are replacing the hose.
i was out of town...and my wife started driving on a water pump that was weeping slightly she didn't notice.. cost me a water pump and a head gasket.... 2k. if i had been in town i could have done the water pump for 150 dollars... oh well. |
Pump side...
Worse comes to worse, you can replace the pump. You do not even need 1/2 inch, may be a 1/4 inch. Do a search...I am sure I posted something about it.
However, if you are keeping the car, buy a new pump. |
Overall these are easy to work on, but some things are difficult, as with most other cars. I think they do it deliberately just to annoy people. ;)
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Thank you!!
I was able to get a hose on there without taking the water pump off. What I did is I went down to Autozone and bought a hose and cut it 1/2 the length as the hose from the dealer. I then sprayed the hose with liquid grease(from Gunk). To my surprise, it fit on with not too much difficulty. As because the length was shorter than normal, I used 3 clamps instead of 2. So far so good. I still have the new-stock hose from Mercedes and plan on replacing if and when the water pump eventually goes. I can't remember when I replaced that pump last so it must be awhile. To my surprise the Mercedes hose is quite thinner than the ones from Autozone. My hunch tells me that the ones at Autozone will last even longer if thickness = durability. |
I told you it was possible...
what do you have to loose...?
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Is the hose from Autozone of two different diameter at each end? I was down this road recently and bought a hose from the dealer. The two ends has different diameter; one is larger than the other. I backed out of pulling the pump at the last minute so I still have the hose sitting in the closet somewhere. So if the hose is the same diameter I wonder how you resolve the fact that the pipe from the engine block is different diameter than the pipe from the pump. But I am glad you did it though, if I have to replace that hose I will attempt your method prior to pulling the pump. |
No the hose from autozone was the same diameter throughout. but note, the diameters of the block pipe and water pump outlet are not that much different and not sure if the accuracy of hose diameters have to be that accurate to work.
In general, the key is to use 3 clamps instead of two. one on both sides, and one in the middle, over where the gap is. |
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cool I was afraid of buying a car with this engine,because of that.
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