Churchill Hydrolastic pump

General Chat with an emphasis on BMC Minis & Other iconic cars of the 1960's. Includes information on MK1 Action days.
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'S'-type
Posts: 175
Joined: Fri Nov 01, 2013 10:59 pm

Re: Churchill Hydrolastic pump

Post by 'S'-type »

Now you tell me Peter!

As you can tell, I'm no engineer. More of a backstreet tin basher

Oh well it was fun mucking around with it and rest assured, no Churchills were harmed in the making of this product.

Good luck with your quest to save the Daleks from extermination!

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111Robin
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Location: Aberdeen Scotland

Re: Churchill Hydrolastic pump

Post by 111Robin »

I'm surprised that the original pumps weren't fitted with a two way valve so that the old fluid could be directed into another container leaving the pump filled with only clean new fluid. However I'm sure they weren't thinking 40+ years ahead hence any cars using the pump would still have relatively fresh fluid in them anyway. I know ours has never been emptied and I certainly don't like the smell coming from the tank. Once I get the Wolsley finished I'm going to have a go at stripping the pump. I still have contacts with several seal manufacturers from work, I'm sure they could come up with something suitable.

ChrisM
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Joined: Thu Jun 24, 2010 1:30 pm

Re: Churchill Hydrolastic pump

Post by ChrisM »

I have a pump sitting at my place. It pumps and wees everywhere, doesn't vac. Gauges are shot. Its not mine and I have a lot on my plate at the moment. But I will check with its owner if it can be stripped. I just can't afford anything else lying around in bits at the moment. I'm in the SE and have milling , turning and grinding facilities.

Chris.

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Peter Laidler
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Re: Churchill Hydrolastic pump

Post by Peter Laidler »

Depending on where you are Chris, it could be a nice winter project for someone in Oxfordshire. Unless you are a concourse freak, a gauge is depression/pressure gauge is a D/P gauge and a cheapo e-bay gauge replaced the pressure gauge I kicked off my pressure washer. In the same way a hand pump is a hand pump and so on

Aussie Bill B
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Re: Churchill Hydrolastic pump

Post by Aussie Bill B »

Andrew1967 wrote:The vacuum side on ours doesn't work either but its not a problem at all.

We pump the suspension up and then let right back down again, which pretty much evacuates all the air. Then re-pressurise and set to height.
The vacuum side of the pump isn't for removing air from the system; it's for pulling the bags up to allow for easy removal of struts, ball sockets, displacers, etc. Once you get 27 inches Hg on vacuum, the vacuum connector has to be removed from the schrader valve and air will move back into the line before it can be repressurised.

As Andrew says, air is removed by pumping up and quickly depressurising several times to remove old fluid and most of the air. Any air left in the system doesn't seem to have any effect.

I have modified my pump to catch old fluid into a soft-drink bottle and not to contaminate the main reservoir of new fluid.
The old fluid can be left standing for a few days to allow the sediment to settle. The clear fluid can be reused.

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Peter Laidler
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Re: Churchill Hydrolastic pump

Post by Peter Laidler »

Not sure that I'd necessarily agree with that Aussie Bill says honourary Aussie Pete the Pom! The machine depresses/vacuums the hydro system to rid it of air. Air is the very LAST thing you need in a hydrolastic system - or it'd be called a hydro-pneumatic system surely! Of course, you can release the air into the system and remove the valves etc etc to do what you want* but when you've done everything, you've got to de-aerate/vacuum/depressurise/evacuate - call it what you want - and then pressurise it with fluid.
Or am I missing something in the explanation?

Obviously you'll never(?) completely de-aerate/evacuate the system and there'll always be a bit of air present (because the physics tells us that the fluid will contain a bit of air) but the 27Hg depression spec quoted in the EMER/manual is the figure that ensures that the HYDRO/FLUID system works at its best. That's my take on things.

I take on board the idea that if you pressurise and depressurise (D&P) the system a few times it will certainly evacuate a lot of the air from the system but believe me, no amount of this D&P will remove all of the air, certainly to the spec given. Basic physics tells us that the air will ALWAYS, always form a natural bubble at the high point. That's what air does. That point is at the inverted U bend where the front displacer hose rises up from the displacer and then down to meet the F to R hydro pipe. Now, if someone could invent a set of front hoses with a small vent-off valve at that point, life could be sooooooooo much easier. But, alas, such an invention is impossible because there ain't no room!

* in my limited experience the average Jo can do most hydro related jobs by depressurising the car so that it bottoms out. In doing so, there's no need to evacuate the system again because if you are careful and follow the simple instructions detailed earlier, no air will have entered while you carefully depressurise the system and none will enter while you pressurise it either, Eureka. A better method of re-using old fluid is to filter it through a good quality coffee filter. But........ unless you can vouch for its SG, you don't know how weak or effective the fluid is. I say always use new.

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111Robin
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Re: Churchill Hydrolastic pump

Post by 111Robin »

Agree. Same principle when evacuating the cooling system then releasing the vacuum to draw in coolant to ensure there are no air locks. The tool I have for this purpose runs off compressed air to create the vacuum then flick the valve to draw in coolant. Never been 100% successful though.

Aussie Bill B
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Re: Churchill Hydrolastic pump

Post by Aussie Bill B »

Peter Laidler wrote:Not sure that I'd necessarily agree with that Aussie Bill says honourary Aussie Pete the Pom! The machine depresses/vacuums the hydro system to rid it of air. Air is the very LAST thing you need in a hydrolastic system - or it'd be called a hydro-pneumatic system surely! Of course, you can release the air into the system and remove the valves etc etc to do what you want* but when you've done everything, you've got to de-aerate/vacuum/depressurise/evacuate - call it what you want - and then pressurise it with fluid.
Or am I missing something in the explanation?

Obviously you'll never(?) completely de-aerate/evacuate the system and there'll always be a bit of air present (because the physics tells us that the fluid will contain a bit of air) but the 27Hg depression spec quoted in the EMER/manual is the figure that ensures that the HYDRO/FLUID system works at its best. That's my take on things.

I take on board the idea that if you pressurise and depressurise (D&P) the system a few times it will certainly evacuate a lot of the air from the system but believe me, no amount of this D&P will remove all of the air, certainly to the spec given. Basic physics tells us that the air will ALWAYS, always form a natural bubble at the high point. That's what air does. That point is at the inverted U bend where the front displacer hose rises up from the displacer and then down to meet the F to R hydro pipe. Now, if someone could invent a set of front hoses with a small vent-off valve at that point, life could be sooooooooo much easier. But, alas, such an invention is impossible because there ain't no room!

* in my limited experience the average Jo can do most hydro related jobs by depressurising the car so that it bottoms out. In doing so, there's no need to evacuate the system again because if you are careful and follow the simple instructions detailed earlier, no air will have entered while you carefully depressurise the system and none will enter while you pressurise it either, Eureka. A better method of re-using old fluid is to filter it through a good quality coffee filter. But........ unless you can vouch for its SG, you don't know how weak or effective the fluid is. I say always use new.
Hello Aussie-Pom Pete.
For the sake of the discussion...
My main point was that when the vacuum connector is removed from the valve on the car, air will pass through the schrader valve anyway, so there will be air present when repressurising.
I used to think about air in the system as you have said. But in over 30 years I've never actually had any issues likely due to air in the system. I think people get far too obsessed about it. I assume the air bubbles are compressed, like CO2 in soft drinks and appear when the pressure is released.
As you say, I suspect that if air in the system was a problem like air in the brake lines and needed to be removed, the factory would have put a bleed valve at the other end of the cars. I think it isn't needed.
1100s had their valves up on the front firewall. If that location was needed for bleeding, the minis would have had them there as well.

Seamist Green 1100
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Re: Churchill Hydrolastic pump

Post by Seamist Green 1100 »

I have never had a problem bleeding off air out of the system without using a vacuum pump. I have proved it worked by using a vacuum pump and finding no air.
Some people just overthink hydrolastics. If you have a vacuum pump use it. If you don't have a vacuum pump just bleed it out.

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iain1967s
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Location: Cambridge, MA, USA

Re: Churchill Hydrolastic pump

Post by iain1967s »

Peter Laidler wrote:Unless you want pin-point authenticity the plastic tank should be simple fix unless it's a high pressure tank but I doubt it.
The old tank is made of some kind of olefin plastic, but of course it pre-dates the introduction of material content labeling regulations so no markings to work from...

I tried four different epoxies to fix the cracks in the old tank. JB Weld Plastic Bonder seems to be the only one which will bond effectively to the original tank.

I also found a similar tank from US Plastic, part number 8819 if anyone else needs similar. It’s 5 US quarts, so around one imperial gallon. Less than the original, but unless you’re running a 1960s BMC dealership I doubt that will be a limitation.
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