Vacuum Pump To Evacuate Air From Coolant System For Coolant Refill?

tinkerman · 09-27-2024, 04:01 PM

Recently, I've been considering getting a vacuum coolant refill kit for use with a compressor, but I started to wonder if it would be possible to pull vacuum "directly"(with a vacuum pump) as opposed to via a compressor + venturi effect (which requires a lot of air)? I searched online and found one account by a motorcyclist* that used a hand pumped oil extractor (Pela 6000 Spherical Oil Extractor) along with a typical vacuum coolant refill system to pull a vacuum on his bike, then refilled coolant with the vacuum.
(*Vacuum filling coolant system )
https://eurokclub.bike/index.php?topic=2805.0

I'm wondering if anyone has done something like this (pulling a vacuum on the cooling system) using a vacuum pump(hand pumped or motorized) connected to a typical vacuum coolant refill kit** on their car? If so, I'd be grateful if you'd share your experience, especially with photos of your set up.
**Note: I'm not asking about experiences with using a vacuum refill kit with the conventional use of a compressor/venturi effect to pull a vacuum.

Cheers~

Mark963 · Yesterday, 04:57 PM

I can't say much on those uses, but I've used unusual vacuum pumps for various fluid changes with a "vacuum jar" - the vacuum port at the top and hose to the bottom for fluid.

I had done some experiments at work where I needed just a small vacuum source to be left on for weeks, so I bought a lousy aquarium air pump and modified it internally so it had the normal air output and also a vacuum connection. I think the first use on a car was to suck the gear fluid out of a differential that didn't have a drain port. That little pump could pull about 6-8inHg of vacuum if I remember right. At that point, the diaphragm would shift too far one way or the other and linear motor wouldn't drive anymore.

Then I bought some tiny motor-piston type air pump off ebay to replace it. 6-12V and those could pull more like 15-20inHg and at high volume. Those tended to be too strong for many purposes of just transferring fluids like I was doing, but running at less than rated voltage seemed OK. A needle valve can always be added as a controlled leak to keep the vacuum from getting too strong.

Venturi pumps are common only because so many people have compressors to power them and they're cheap and robust. But in the end, it's about how much pressure and at what volume are you trying to move. Vacuum and pressure are just vacuum and pressure. You can make all sorts of non-standard approaches work.

09-27-2024, 04:01 PM	#1
tinkerman Private First Class 62 Rep 108 Posts Drives: '07 320i (E90) Join Date: May 2013 Location: Korea iTrader: (0)	Vacuum Pump To Evacuate Air From Coolant System For Coolant Refill? Recently, I've been considering getting a vacuum coolant refill kit for use with a compressor, but I started to wonder if it would be possible to pull vacuum "directly"(with a vacuum pump) as opposed to via a compressor + venturi effect (which requires a lot of air)? I searched online and found one account by a motorcyclist* that used a hand pumped oil extractor (Pela 6000 Spherical Oil Extractor) along with a typical vacuum coolant refill system to pull a vacuum on his bike, then refilled coolant with the vacuum. (Vacuum filling coolant system ) https://eurokclub.bike/index.php?topic=2805.0 I'm wondering if anyone has done something like this (pulling a vacuum on the cooling system) using a vacuum pump(hand pumped or motorized) connected to a typical vacuum coolant refill kit* on their car? If so, I'd be grateful if you'd share your experience, especially with photos of your set up. *Note: I'm not asking about experiences with using a vacuum refill kit with the conventional use of a compressor/venturi effect to pull a vacuum. Cheers~ Last edited by tinkerman; 09-28-2024 at 11:37 AM..*
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Yesterday, 04:57 PM	#2
Mark963 Private 30 Rep 77 Posts Drives: 2011 328i Join Date: Jun 2018 Location: Iowa iTrader: (0) Garage List 2011 BMW 328 [0.00]	I can't say much on those uses, but I've used unusual vacuum pumps for various fluid changes with a "vacuum jar" - the vacuum port at the top and hose to the bottom for fluid. I had done some experiments at work where I needed just a small vacuum source to be left on for weeks, so I bought a lousy aquarium air pump and modified it internally so it had the normal air output and also a vacuum connection. I think the first use on a car was to suck the gear fluid out of a differential that didn't have a drain port. That little pump could pull about 6-8inHg of vacuum if I remember right. At that point, the diaphragm would shift too far one way or the other and linear motor wouldn't drive anymore. Then I bought some tiny motor-piston type air pump off ebay to replace it. 6-12V and those could pull more like 15-20inHg and at high volume. Those tended to be too strong for many purposes of just transferring fluids like I was doing, but running at less than rated voltage seemed OK. A needle valve can always be added as a controlled leak to keep the vacuum from getting too strong. Venturi pumps are common only because so many people have compressors to power them and they're cheap and robust. But in the end, it's about how much pressure and at what volume are you trying to move. Vacuum and pressure are just vacuum and pressure. You can make all sorts of non-standard approaches work.
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