300GE very slow coolant leak

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reddevil
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I have a very slow coolant leak on my 300GE. Probably about 1l per 1000 miles driven. No oil in water or vice versa.

I added some of the radiation dye to the coolant so see where it was coming from - it looks like it is coming from somewhere at the front near side of the engine, running down the block and collecting on the front ARB and sump. Looking up under the vehicle it appears there are two hoses that travel up that route to somewhere under the air filter/throttle body area but I can't see exactly without dismantling absolutely everything.

Radiator is new and head gasket etc. all done within the last 5000 miles so my assumption is this is an old hose.

Anyone care to offer an opinion on the two hoses I mentioned? Where do they terminate? Tips before I rip into taking the pancake air filter housing and whatever else apart to investigate further?

Pistonhead
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Re: 300GE very slow coolant leak

From the 300GE; all I can ascertain that you have a W463 - 300GE which is likely to be the M103 engine. 

Most probable coolant leak in particular if you say it emanates from the front, running down the anti-roll bar and sump is the water pump. These have a tendency to be self sealing and in the early stages of leak, the leakage is for a short periods during warm up and cooling of the engine when switched off. Inbetween these periods the leak seals up hence difficult to find. Assuming all hoses are tight and integrate.

The leak drains from a hole manufactured to the pump body at a its bottom in the 6 O'clock position.

Other small leakages tend to be the heater valve, or hoses connecting to and, or heater matrix itself. - Windscreen tends to condensate and water in either driver or passengers foot well with possible order of antifreeze. 

Keep a regular check on coolant level until you cure the problem. Replenish on a cold engine - DO NOT open the expansion bottle cap when engine is hot!

At the front, side (O/S) of the water pump there is an O-ring seal fitted to a metal water pipe, these could leak but rare. 

If the rubber hoses you mentioned are the one I envisage, these are the induction hoses; part of the idle circuit and carry no coolant.

reddevil
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Re: 300GE very slow coolant leak

 

The leak is trickling down those hoses - but not necessarily coming from them.

Yes car is a G463.

I am pretty sure the water pump has been done recently with the head work but yes makes sense to investigate that next. It probably won't have been a genuine Mercedes replacement.

Arnie
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Re: 300GE very slow coolant leak

 

I think Rakesh is correct in his analysis. Was  the replacement water-pump an original MB part or an aftermarket one? I replaced one on the same M103 engine  last year and found that most aftermarket versions are not built like OEM,


You might want to verify that the pump was fitted correctly with its gasket and that the hoses are correctly tightened... and that the O-ring in the thermostat housing is in place.

 

 

Pistonhead
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Re: 300GE very slow coolant leak

My memory is having difficult in envisaging the two hoses you have mentioned.

Are you able to post up any photographs of it. Unfortunately the Russian EPC site has shut down; my main free access to EPC from which I could derive much information.

reddevil
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Re: 300GE very slow coolant leak

I'll take a photo of the hoses tomorrow, I'm going to start pulling parts off for a closer look.

Looking through the history the thermostat and water pump were apparently replaced at the top end rebuild less than 10k miles ago. But not clear if MB genuine parts or not. Radiator is def new, it looks it and I have a receipt.

I've just topped up 1l of coolant, it's probably taken about 500-1000 miles to loose that much.

I checked with MB for an pump, over £240 for a recon one! So warrants confirmation this is the problem before we start chucking that kind of money after it 

If it turns out the one on my truck is a MB one, anyone know anywhere reputable to have it reconned?

Chris

 

reddevil
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Re: 300GE very slow coolant leak

We used a boroscope camera and traced this to the rear of the water pump - there is a circular section held on with 3 bolts (not sure why) and it's leaking out of there when cold, seals when hot,

My mechanic put a screwdriver to the pump body when the engine was running and declared the pump quiet so he assumes there is an o-ring or something behind that cover. His recommendation given the pump is quiet is to add some K-Seal to the coolant and see if that stops it, rather than rip everything apart to fit a new pump.

 

g wagon g
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Re: 300GE very slow coolant leak

It would be better to fix it properly and not add any sealant

Sealant often does more harm than good as it blocks radiator core and heater matrixes and any small water ways

Radweld was the worst and K seal not as bad. We have done many engines and had to clean out small important waterways where people have added the wonderful miracle cures. If it was me i would just fix it properly once and for all and forget about it

g wagon g
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Re: 300GE very slow coolant leak

If its had a new pump then surely the pump will be fine for many 10000s miles. Is it not just the seal that need doing as perhaps they used the old one and did not replace with new

Arnie
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Re: 300GE very slow coolant leak

There is a bit of work to replace the water-pump, in removing all the other parts for access, but best to do things properly, if you want a good result.

Pistonhead
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Re: 300GE very slow coolant leak

Not sure on this K seal but I generally do not favor such sealants as they could block up the radiator cores unless in emergency but not as a fix.

Renew the water pump.

reddevil
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Re: 300GE very slow coolant leak

So I am finally going to invest in a new water pump.

A "recon" one from Mercedes direct is over £250 which is ridiculous.

There are various ones online from GSF and others like a Meyle german-manufactured item at about half the cost.

However ones listed for the M103-engined SL seem cheaper still. From the diagrams these seem to be exactly the same type of pump.

Is there anything specific about the M103 engine in the G which means a pump from another M103 model won't fit?

Thanks,

Chris

prwales
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