devilinblack

Last weekend I drained the radiator and block and pulled the radiator. I noticed that the last of the water draining out was rather dark, even though it had only been a couple of months since I last drained and filled the system. I used a hose and ran hot water forwards and backwards through the system until it flowed clear and put everything back together, filled with distilled water and a water wetter/lube product. I ran the car for maybe 20 minutes before deciding I needed to pull the front end off again because I still had oil leaks. Anyway tonight when I drained the radiator I got the same thing, gray cloudy water at the end of draining the radiator.

I've never had any cooling problems so it's not urgent and I don't want to risk breaking anything, but is there something I can use to help flush out the inside of the radiator, maybe white vinegar to clean up some deposits?

Lizard928

To properly clean the rad you have to remove the end tanks and verify each channel is properly flowing.

Mike Frye

Stephen,

Is there a leak between the oil cooler and the core, is it oil that's getting into your coolant (in which case I assume there would also be coolant in your oil)? I don't know if the '78 has an oil cooler or not, I'm just curious.


Also, this is a timely thread. Does anyone know how much pressure you need to use to pressure test a radiator? I took mine to the shop and they told me I had core leaks, but the only leak I was aware of was the side tank gasket. I'd like to check mine and another one on my own but I don't know how much pressure to use.

Not trying to hijack your thread Steve, maybe it will help you test your tank while it's out also.

devilinblack

I don't have an oil cooler, so no chance of that. The majority of the water coming out looks clean and the water out of the block is clean it's just the last little bit out of the radiator that's a little grungy. I'm probably just being paranoid.

On the other hand, I did find a couple instances on line last night of people with extensive hard water deposits throughout the system that filled the whole thing up with vinegar, ran the car until hot, let it sit overnight and then thoroughly flushed. No way I'm going to try that on the 928, but it's food for thought.

Ben

My Mercedes workshop manual recommends to use a citric acid solution in the cooling system to clean it out. The car has an aluminium engine, so can't be too dissimilar to the 928. As far as I remember though, its only left in there 30 mins, then flushed with clean water.

I did do it once, but it didn't clear the radiator. I ended up having to buy a new one.