noud

Hi family,

My 00 S500 started to lose coolant. Sometimes it took 3 days to empty reservoir sometimes a week, sometimes it was leaking while parked sometimes did not even leak while left in parking lot for days. I saw obvious leak from upper hose with this weird plastic adapter lock: replaced it with OEM one and now it does not leak anymore, so I was happy that i fixed it. But it still leaks and I dont know from where. Are there any common well known weak points I can look into, because I cant catch from where its leaking and why its random.

tusabes

noud

I left my car sitting for over a week, and I kept it running for 15 minutes, with heater on and off watching for leak, and nothing. no warning light no leaks. I guess leak happens depending if car is uphill or downhill. Ill park it tonight downhill to confirm that. But how thats possible?

wallyp

IF the leak is at the heater hose connector leak at the front firewall, it usually leaks only when the engine is running above idle speed. The leakage is above the lower engine covers, and a small amount of leakage might well be trapped in the engine covers, and not immediately drop to the ground.

noud

I took for a test drive and no leaks from that plastic hose. But I saw obvious leak from beneath the coolant reservoir where it somehow attaches to the windshield water reservoir and it was wet around the electric pump connected to the windshield reservoir. Are these two reservoirs connected or are there any weak points below coolant reservoir?

wallyp

I was losing coolant from my 2003 S430, and could not see any trace of leakage from the heater hose bulkhead fitting - until I took it out and examined it very closely. Only at that point could I see an ultra-fine hairline crack in the fitting.

The only connection between the washer fluid and the coolant is the coolant loop that runs into the washer tank to warm the washer fluid. There is not a connection near the bottom of the washer tank. It is common for there to be washer fluid leaks at the grommets for the washer pumps.

noud

Okay, so I replaced heater exchange hose fitting and while doing it. No visible damages were present which might caused the leak, only small crack but I doubt it was the issue. Also I replaced the grommets for washer pumps. Hope, leak will go away.

https://drive.google.com/file/d/1Uad...ew?usp=sharing