Refilling coolant - vacuum bleeding
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From: Emmett, ID, USA
2007 GL450
Refilling coolant - vacuum bleeding
I have noticed that refilling with coolant is unnerving: the motor seems to maintain pockets of air, and even with a burping funnel coolant will overflow, probably because of coolant boiling in certain pocket places. You can't leave the radiator cap off, or warm coolant will bubble up and out all over the place. That can't be healthy for the motor, right?
I noticed that WIS specifies vacuum bleeding and filling. The vacuum bleeder is cheap ($32), but requires a reasonable air compressor. I picked one up from Amazon and it seems to work well, despite missing fittings (I returned it).
Just thought I'd pass that along. Simply filling from the reservoir does not seem to work all that well.
I noticed that WIS specifies vacuum bleeding and filling. The vacuum bleeder is cheap ($32), but requires a reasonable air compressor. I picked one up from Amazon and it seems to work well, despite missing fittings (I returned it).
Just thought I'd pass that along. Simply filling from the reservoir does not seem to work all that well.
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From: Republic of Texas
'99 and '05 E55 AMG
Vacuum filling is the way to go but be advised an older vehicle's o-rings may be marginal due to age. I discovered this on my '05. Traced it to a heater valve o-ring that failed after pulling vacuum; ended up replacing the entire valve although replacing the o-rings would have been sufficient. Have a backup plan.
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2007 GL450
I've replaced the coolant reservoir, thermostat, and two idler pulleys, drained coolant in the radiator and re-filled with new coolant. Just the normal burping procedure. and then rechecked coolant level and refilled the reservoir after 1 day of driving. That was over one year ago and things are working fine.
Thread Starter
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,762
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From: Emmett, ID, USA
2007 GL450
Vacuum filling is the way to go but be advised an older vehicle's o-rings may be marginal due to age. I discovered this on my '05. Traced it to a heater valve o-ring that failed after pulling vacuum; ended up replacing the entire valve although replacing the o-rings would have been sufficient. Have a backup plan.
The only question being, how close was that o-ring to failure anyway. It might be a good idea to trigger failure in the shop rather than on the road.
Last edited by eric_in_sd; Oct 9, 2023 at 08:24 AM.
Thread Starter
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,762
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From: Emmett, ID, USA
2007 GL450
I've replaced the coolant reservoir, thermostat, and two idler pulleys, drained coolant in the radiator and re-filled with new coolant. Just the normal burping procedure. and then rechecked coolant level and refilled the reservoir after 1 day of driving. That was over one year ago and things are working fine.
Running to warmup with the reservoir cap off seems to lead to overflow, presumably from steam expansion.
Maybe I have been overthinking it. idk.
Thread Starter
MBWorld Fanatic!
Joined: Jun 2010
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From: Emmett, ID, USA
2007 GL450
Running to full warmup and pressurization still burped out air, leading to a Top Up Coolant message, so I am a little skeptical of the benefits of vacuum purging. I don't see that it is a whole lot better than simply filling the expansion tank most of the way full while idling, then capping the tank, followed by running at a high idle for a few minutes to purge the air, until coolant temp does its customary temperature overshoot followed by stability.
The high idle seems to be necessary. On one of these go-rounds, I noticed the radiator fan kicking on. I checked the temp and it was above 220 - don't remember the exact number - and as soon as I revved the motor, the temp dropped back down. Conceivably that was the thermostat sticking, but I don't recall the fan going on full speed at idle warmup before.
It would be nice to have a known good conventional refill procedure. The vacuum apparatus is nifty, but it is a lot of work to set up, tear down, and clean up afterward.
The high idle seems to be necessary. On one of these go-rounds, I noticed the radiator fan kicking on. I checked the temp and it was above 220 - don't remember the exact number - and as soon as I revved the motor, the temp dropped back down. Conceivably that was the thermostat sticking, but I don't recall the fan going on full speed at idle warmup before.
It would be nice to have a known good conventional refill procedure. The vacuum apparatus is nifty, but it is a lot of work to set up, tear down, and clean up afterward.
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Mercedes gl450
It has seemed to me to be a struggle. You want to refill the reservoir with enough coolant that you don't run dry in first warmup, but not so much that it does not leave coolant expansion space during warmup.
Running to warmup with the reservoir cap off seems to lead to overflow, presumably from steam expansion.
Maybe I have been overthinking it. idk.
Running to warmup with the reservoir cap off seems to lead to overflow, presumably from steam expansion.
Maybe I have been overthinking it. idk.
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From: Albuquerque
'10 CL550, '12 GL550
Will revive this thread simply because the title could aid future searching and it's applicable to my current question.
My recently purchased GL550 has incorrect coolant (thanks Christian Brothers) and I'd like to get the correct blue G48 in there.
However, working at home there is no way I can access block drains and it looks pretty iffy even to access the radiator drain.
So, the question I've never seen answered anywhere (or even asked) ... will a vacuum refiller such as Airlift II serve to extract the current coolant? I note cryptic sentences stating there could be some residual that spits out when first creating the vacuum, but not sure this is equal to extracting, in this case, 12 liters.
Anybody?
My recently purchased GL550 has incorrect coolant (thanks Christian Brothers) and I'd like to get the correct blue G48 in there.
However, working at home there is no way I can access block drains and it looks pretty iffy even to access the radiator drain.
So, the question I've never seen answered anywhere (or even asked) ... will a vacuum refiller such as Airlift II serve to extract the current coolant? I note cryptic sentences stating there could be some residual that spits out when first creating the vacuum, but not sure this is equal to extracting, in this case, 12 liters.
Anybody?
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Thread Starter
MBWorld Fanatic!
Joined: Jun 2010
Posts: 2,762
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From: Emmett, ID, USA
2007 GL450
You're thinking to hook the vacuum bleeder up to the radiator drain, right? I bet you could. Hook up the exhaust fitting to a hose going into a jug. Make it secure; the output will be a mess! It will come out as a spray, mixed with lots of air.
But first I'd make absolutely sure the coolant is not compatible. Coolant is tricky chemically, and some are cross-compatible and some aren't.
But first I'd make absolutely sure the coolant is not compatible. Coolant is tricky chemically, and some are cross-compatible and some aren't.
