Coolant leak

[Almomen]

My e500 leaks water some how, I fill the expansion tank the car runs smoothly with no issues after few days the coolant light comes until it comes to a level that when I am in traffic the car overheat. Recently the upper and lower hose were changed with original parts,
Any hints

 

[gsxr]

Pressure test the cooling system to find out what is leaking, if there's no obvious leak point.

If your windshield washer reservoir level is rising, the washer bottle thermostat either has failed O-rings, or has cracked... it's is a possibility that could be where your lost coolant is going, if there is no external leak.

 

[nocfn]

and I might add, if you turn on your washer/wipers and give you several squirts, if you have coolant [glycol anti-freeze] in the washer tank you will have bad streaking from coolant on your windscreen.

 

[Almomen]

i doubt it could be from the windshield reservoir, however, i noticed that there is a pressure in the coolant tends to get the coolant fluid out once I open the coolant cap even though the car is cold , which is weird for me to notice.

 

[Almomen]

As if there is no relief tube to get this residual pressure , or the possibility that this tube is clogged

 

[gsxr]

As if there is no relief tube to get this residual pressure , or the possibility that this tube is clogged

The system is sealed, there is no relief for residual pressure, the system will remain pressurized until the cap is removed.

 

[Almomen]

Ahh, but I see what is look like a relief tube from the bottom of the coolant and then over towards the fenders and I guess down to out side. I thought every car has this

 

[gsxr]

Ahh, but I see what is look like a relief tube from the bottom of the coolant and then over towards the fenders and I guess down to out side. I thought every car has this

That is the overpressure relief to the fender in the reservoir. When system pressure exceeds the rating of the cap (normally 1.4 bar) coolant is allowed to go out the 8mm hose to the fender reservoir. Exceeding 1.4 bar typically will never happen except near overheating temperatures (~120°C).

 

[nocfn]

could you have extra air in your system which shows a full level until that fluid heats up rendering you under level.....

 

[nocfn]

There is an overflow tank inside the fender well. Still a sealed system, but what goes in that overflow will come back in the system at some point.

 

[Almomen]

Thanks this is new to me, so what is it then that makes warning lights comes out and frequently have to fill it with coolant? Initially it was the resistor which failed to operate the low speed auxiliary fans. Then it was changed and worked fine and temperature was with in limit , but why the coolant continue to reduce?!

 

[nocfn]

You either have a leak or you have air in your system that you need to get out. What does the engine oil look like? Is it whiteish or frothy? How old is your radiator cap? Check the hoses in and out of the firewall for leaks, Get your car's front end up higher than the back. Not crazy high, but like the slope backing out of the garage into a driveway. Keep car running with the bonnet in service position, defroster on full fan and the windows closed door shut. Inspect the hoses, giving them a squish periodically while the car gets to temp. (thought bubble is I hope you are running the car with a thermostat) As the car reaches temp it may take longer as the coolant is flowing thru the heater core and the fan is blowing air thru it. Your Temp will get hot however, and if you have a thermostat in there if it is working..it will open and flow will be robust and the roar of the fan clutch will be noticed without fail (if it is working). Monitoring these hoses at the firewall, the expansion tank and the radiator all the while. If you do not have visible leaks then you may have air in your system or whitish frothy oil if you have a head gasket leak. If you have humidity evidence on your windscreen at temp, you may have a heater core that is suffering in some way. If it was leaking you would have musty sweet/sour mash smell perhaps with evidence of moisture blown on the inside windscreen near the defroster vents. Wile this is not likely your issue, running green style coolant can and has more often than not proven to eat away at the aluminum core and pipes as the coolant sits in those components during mild temps. Hopefully not your case. The over flow bottle in the PS fender well should be looked at. The original hose off the expansion tank into the fender well is hot and brittle over time and can be a leak source. It is just a tire removal and some fender liner nuts to remove to gain access there. if you have a hose leak it will be evidence of it very clearly. If the hose is brittle, any rubber hose from the local mcflaps store will do as long as the ID/OD are the same and the rating is proper for the fluid. Your need to pay attention to the circuitry of the hoses heading into and out of the firewall and also the washer tank reservoir and heating to the wiper system hoses/

Please tell us your findings - others will benefit.

 

[gsxr]

Thanks this is new to me, so what is it then that makes warning lights comes out and frequently have to fill it with coolant? Initially it was the resistor which failed to operate the low speed auxiliary fans. Then it was changed and worked fine and temperature was with in limit , but why the coolant continue to reduce?!

You have a leak somewhere, and need to find out where the coolant is going. As stated back in post #2, you do this by pressurizing the system to 15-20psi with a tester and see where the cooling is leaking, assuming the reservoir level drops along with a reduction in pressure as shown on the gauge of the tool.

Amazon.com : coolant pressure tester

 

[TerryA]

@Almomen,
You mentioned that you recently changed the upper and lower hoses. I don’t know the temperature change from day to night where you are but I have experienced radiator hoses leaking at night when the temperature drops. It required retightening the hose clamps. If it didn’t leak before you changed the hoses I’d be looking at the hose clamps.

 

[rayhennig]

As stated back in post #2, you do this by pressurizing the system to 15-20psi with a tester and see where the cooling is leaking

100% this. I bought a test kit, not rubbish quality, for about 80€. Well worth it. I found 2 collars that needed to be tightened - those leaks stopped.

But there was another, from the radiator. Nissens replacement installed and all well 18 months later.

This on a '91 300-24.

Good hunting.

RayH