Hey guys, I just changed the upper and lower radiator hoses and was curious what is the best procedure to burp the coolant system of the trapped air??

Thanks In advance,
David

 

Bump.

 

I've had the radiator out on each one of my 240s and I've never had to "burp" it. All I did was to refill, run the engine till it came up to temp on the temp gauge and checked the upper radiator hose to ensure that the thermostat had opened. All this performed on level ground. Also turned the heat on full blast to make sure the air was removed from the heater core.

 

yeah, just leave the pressure cap off the expansion tank when you first start it, and all the air bubbles up to there, top it off as it empties. once it starts to warm up, put that cap back on, and keep an eye on it. as long as there's SOME fluid in said expansion bottle, you're OK, you don' thave to obsess over keeping it full to the max mark while you're doing this..

 

hey pierce. thought i'd hit you up over here in case for whatever reason this ends up being a better place for you to hold forth on (and/or for us to go back and forth on) best practices for coolant system flush and refill. again, i've got a 1990 740 GL. thanks.

 

been too long since I did one, that I don't remember specifically what I did. mostly I think I opened the heater valve, and disconnected the lower big hose at the radiator, caught as much of the coolant that dumped out in a pan for disposal, removed the thermostat and used a garden hose with a big rubber ball end fitting to force water into the system til it ran clear, same with the radiator, let all that drain out, put it all back together with a new thermostat, and filled it with the usual 50-50 mix of G-05 and distilled water, then let it run for a few minutes with the fill cap off and all the air came out. oh theirs a drain plug on the right (exhaust) side of the block, just behind and below the oil filter, open that to drain the lower block after dumping most of the rest of the coolant, and leave it open while flushing but remember to close it before refilling and starting.

I only did the full flush once to a car that had been neglected, usually I just dumped what would dump, and refilled with fresh, and did that at least once every 3 years, good to go.

 

Hey pierce. Thanks for this step-by-step, particularly the rubber-ball hack. I am definitely looking at a situation of long-neglect. In the process of taking out a broken thermostat and putting in a new one and taking that new one out again (turns out it was not OEM after all, so was not a true fit), I'm sure I've come close to dumping/swapping out all the old coolant, but the coolant in the reservoir is still turning up filthy all the requisite burping and swishing. So, full flush coming up this weekend. (I might leave the petcock alone for now though... unless you strongly recommend it in cases like mine...)

 

If you are seeing burping and swishing of coolant in the reservoir when the engine is running then you have a blown head gasket.