[e91Owner]

I use a lift to service my 2011 e90 & 2010 e60 at a nearby military base. By the time it gets there it's super hot so waiting for the engine to cool enough to properly drain the radiator and the block takes forever.

I decided to try something new... sort of a power bleed with the electric pump. To do this, I:
1) disconnected the return hose from the expansion tank.
2)removed front air intake scoop to get access to full length of return hose. (Two torx screws)
3) unclipped return hose—gives you about 3 feet of play.
4) filled expansion tank to max with 50/50 mix and started the venting procedure in the normal fashion.
5) kept tank full with 50/50 mix until the return was blue (had to restart the water pump once. It seemed to stop cycling after a gallon).
6) turned off car to stop pump cycling.
7) reattached hose to tank
8) repeated vent procedure

Is there a downside to doing it this way? Since the venting procedure purges the block cavity of air, my assumption is that the fluid is cycling through all of the nooks and crannies. Certainly a heck of a lot easier, and absolutely no mess. Basically the same as bleeding the brakes, if this worked correctly. Also, Step 8 wouldn't really be required unless you let the tank go dry. I just did it for good measure. All in all, took 30 mins.

Also, I used a cheap transmission fluid bottle hose to keep the tank full as it bled. Easy to control and you can see the level in the tank. The G-48 fluid from valvoline is pre-diluted, BMW-approved and was $12 at Walmart.

[e91Owner]

Bump

[alfazrus]

I mean , you already did it. You should be the one telling us if there is a downside to doing it that way in near future, no? If there is, it's kind of late.

[e91Owner]

Originally Posted by alfazrus

I mean , you already did it. You should be the one telling us if there is a downside to doing it that way in near future, no? If there is, it's kind of late.

Lol.... by downside, I mean relative to the coolant path. I'm assuming that the venting cycle flows through the entire loop, thus purging the entire system. Obviously there will be some amount of mixing, but I wouldn't think any more than the TIS fill procedure.

The final streams were clear blue and a standard bulb tester reads the coolant in the advertised range.

Side note, on my e60 xdrive, the coolant pumped way faster, still easy to keep up with the level in the expansion tank. Took 5 minutes to change the fluid.

[Efthreeoh]

I don't see any real issue with it other than using more coolant and not being sure all of the old coolant is removed from the system, and risk of battery discharge (solved with hooking up a second battery). But a few questions:

1) If you have to wait for the cooling system to cool down before a conventional drain procedure, how is it you can open the return line to the reservoir tank without it spewing hot coolant from the hose end and the bib on the reservoir?

2) Do you plug up the reservoir opening? Seems to me coolant would come out the bib for the return line.

[e91Owner]

Originally Posted by Efthreeoh

I don't see any real issue with it other than using more coolant and not being sure all of the old coolant is removed from the system, and risk of battery discharge (solved with hooking up a second battery). But a few questions:

1) If you have to wait for the cooling system to cool down before a conventional drain procedure, how is it you can open the return line to the reservoir tank without it spewing hot coolant from the hose end and the bib on the reservoir?

2) Do you plug up the reservoir opening? Seems to me coolant would come out the bib for the return line.

1) I'm doing this on a cool engine in my garage. I only work on my cars with a lift if it requires getting underneath which is why I was trying this out. Having to wait for the engine to cool while I'm paying for lift time was no good.

2). If you look at the picture and my comments, you'll see that I used a transmission filler hose on the gallon jugs. It allowed me to keep the tank filled, but not overfilled, since I could see the coolant level in the tank. You could also get one of those coolant tank funnels that screws on and cap the return if you wanted to dump more in at once.

Also, people that complain of the venting procedure draining the battery must have really weak batteries. Even if the pump was on continuously for 12 minutes instead of just cycling, I can't imagine it draining it that much. I didn't hook either of my cars up to my charger and ran 3 cycles. Didn't notice anything.

Pretty similar conceptually to bleeding the brakes without a pressure bleeder.

[Efthreeoh]

Originally Posted by e91Owner

1) I'm doing this on a cool engine in my garage. I only work on my cars with a lift if it requires getting underneath which is why I was trying this out. Having to wait for the engine to cool while I'm paying for lift time was no good.

2). If you look at the picture and my comments, you'll see that I used a transmission filler hose on the gallon jugs. It allowed me to keep the tank filled, but not overfilled, since I could see the coolant level in the tank. You could also get one of those coolant tank funnels that screws on and cap the return if you wanted to dump more in at once.

Also, people that complain of the venting procedure draining the battery must have really weak batteries. Even if the pump was on continuously for 12 minutes instead of just cycling, I can't imagine it draining it that much. I didn't hook either of my cars up to my charger and ran 3 cycles. Didn't notice anything.

Pretty similar conceptually to bleeding the brakes without a pressure bleeder.

I got the part about paying lift time while waiting for the engine to cool, however you weren't clear you did this cold and still not going to the military base to work on your car.

So I still have a question about, if the return line is disconnected from the reservoir, is there not a chance coolant will spill from the return line opening at the reservoir? I understand the N2 cooling system quite well. The water pump pulls (draws) cool coolant from the lower radiator hose and pumps it into the lower part of the engine block up to the head. The reservoir feeds the system at the thermostat. Some hot coolant goes back to the T-stat through the T-stat hose that attaches to the head. Hot coolant also goes from the head (through the OFH) to the radiator via the upper radiator hose. The issue I see is the coolant return line is in the system primarily use to return air to the reservoir during the bleed process. That's why it sits on top of the upper radiator hose; air takes the least path of resistance at the highest part of the cooling system, so it separates from the coolant at the upper radiator hose elbow. So I'm not sure all the old coolant gets out of the system with your method.

[e91Owner]

Originally Posted by Efthreeoh

So I still have a question about, if the return line is disconnected from the reservoir, is there not a chance coolant will spill from the return line opening at the reservoir? I understand the N2 cooling system quite well. The water pump pulls (draws) cool coolant from the lower radiator hose and pumps it into the lower part of the engine block up to the head. The reservoir feeds the system at the thermostat. Some hot coolant goes back to the T-stat through the T-stat hose that attaches to the head. Hot coolant also goes from the head (through the OFH) to the radiator via the upper radiator hose. The issue I see is the coolant return line is in the system primarily use to return air to the reservoir during the bleed process. That's why it sits on top of the upper radiator hose; air takes the least path of resistance at the highest part of the cooling system, so it separates from the coolant at the upper radiator hose elbow. So I'm not sure all the old coolant gets out of the system with your method.

To answer your question about it spilling out—no. It will not in the method that I describe since the return line fitting is really high on tank. You can way over fill it so that the float is at its max position without it coming out of the hole. Plugging it would be pretty easy, though. It's part number 11531436850. Like $4 from fcp.

Your comments about the coolant path make it sound like this works pretty well. My last fill was with HT-12, green. This g-48 mix was blue. When it started streaming straight blue is when I stopped the filling and ran the venting sealed. Didn't need to add any coolant since the only air in the system was the small amount in the return line to the tank.

In any case, super easy, super clean and probably at least a 90 percent solution whereas ISTA/TIS is probably 95%. I don't think my car knows

[e91Owner]

Side note, used just shy of two gallons to get it steady blue.

[Mark963]

I emptied mine at the radiator and figured it left about 2.88 quarts. I drained it and filled it with distilled water and then ran the bleed to mix the fluid through the system, repeating that whole process 3 times. Then I drained it and filled it with a good bit stronger than 50/50 to account for the trapped 2.88 quarts that was mostly water at that point. I ran the bleed process twice and then drove it for a few days. Then I checked the coolant concentration with a refractometer and found that it had dropped from the reading I got from the reservoir immediately following the last bleed, but it was about as strong as the original fill - around -42F. The pH of old and new fluid was around 7.5. For the refill, I used 1 gallon and half of a quart of BMW fluid (not pre-mixed).

I'm not sure how the process I followed compares to your flush method, but you undoubtedly saved a lot of time.

FWIW, I used a "Kill a Watt" meter on a server supply to power the car while performing the bleed process. The supply is probably around 80% efficient and it was pulling about 310W at the peak of the bleed process, which is only a small fraction of the entire bleed process. I thought I'd read somewhere that the N52 pump runs up to 200W and the N54 runs up to 400W, but I could remember incorrectly. I wouldn't expect a couple cycles of that to do much to the battery.

[e91Owner]

That's what I would call the flush method which I have used on other cars as well. The unknown is always the concentration. In your case, it sounds like you are a little heavy on the coolant. Ph should be around 8-9 for a 50/50 mix. Ph is 7.1-7.3 at full strength.

The valvoline G-48, which is BMW approved, can be purchased in a 50/50 mix at Walmart and most auto parts store as cheap as you can get the BMW undiluted G-48.

On a side note, no change in fluid levels after a week refilling via the pump method I described. That's what I expected as no air should have entered the system.. just confirmation.

[Emilime75]

Originally Posted by e91Owner

.

The valvoline G-48, which is BMW approved, can be purchased in a 50/50 mix at Walmart and most auto parts store as cheap as you can get the BMW undiluted G-48.

So, Walmart/Valvoline is twice as expensive as BMW?

[e91Owner]

Originally Posted by Emilime75

So, Walmart/Valvoline is twice as expensive as BMW?

Sorry, could have said that better. The 50/50 valvoline G-48 price per gallon is about 1/2 the cost of the undiluted BMW G-48, so you end up spending the roughly the same amount for the same price for the same amount of mixed coolant. Actually, valvoline would be slightly less since you don't have to buy distilled water.

[jind77]

Wow saved me lot of time