Churchill Hydrolastic pump

['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!

[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]

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.

[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]

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.

[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.

[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]

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]

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.

[iain1967s]

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.

[Seamist Green 1100]

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 for different epoxies to fix the cracks in the old tank. JB Weld Plastic Bonder seems to be the only one which will bond.

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.

Great stuff!

I will keep the US plastic tank in mind.
I have an Australian Austaloy pump which is the local copy of the Churchill. They have a soldered metal tank in place of the plastic tank. Mine was rusty as heck so I soldered all the holes and painted the inside with epoxy. I don't think it will last forever.

[Supersonic]

I've a mate who collects Churchill hydrolastic pumps I bought one of him on Monday and he went immediately to view another one he knew was for sale

I remember being told some years ago that when hydrolastic cars first appeared in 1962 only BMC dealerships had hydrolastic pumps, would that be correct?

Alan

[iain1967s]

For the custom seals on the pump pistons that are NLA, the originals will need to be reused. Classic motorcycle restorers rejuvenate rubber parts by a week's soaking in rubbing alcohol + wintergreen oil mix (3:1 ratio). I've never tried that but it's worth a shot.

Update 13 Dec:
I've had the seals soaking in that mixture for a couple of weeks, and the rubber definitely seems to have softened up and swelled a little. I am going to reassemble both of the pumps at the weekend, and see if they will hold pressure and vacuum.

Update 18 Dec:
The special two-part shaped seal in the pressure pump is held in place by a rubber cone reinforced with fiber. These all seem to have recovered well with their soaking in the mixture, and now seal correctly when reinstalled in the pump. See bottom photo of the reassembled pressure pump before the front plate is re-fitted.

The plain seal between the vacuum pump piston and bore did not fare so well. Although the rubber swelled up and softened in the mixture, it does not have any fiber reinforcement to hold it in shape. The result was a seal that swelled well beyond the correct 1.5" outside diameter, and it broke up when I tried to compress it back into the bore.

So now I am looking to replace the vacuum seal with a modern hydraulic type. I've ordered a few different sizes off eBay to see what fits best. Will post the results back to this thread once I get it figured out.

Update 27 Dec:
I found a modern hydraulic seal which fits perfectly. It's listed as "Hydraulic Rod/Piston Seals 1/4"CS x 1"ID x 3/8"HT Type" and is MFP Seals part number XP-250-01.000-375BU2145, the yellow,part in the attached photo.

The original vacuum seal consists of three layers : a fiber spacer, the broken rubber seal, and another fiber spacer, all sandwiched together under compression by a brass plate and nut.

The new seal is not quite wide enough to replace all three of the original parts, so I used a plain Neoprene 1.5"x1"x1/16" washer (E15010116) against the open face of the new seal, so that the brass plate and nut have something to compress against.

For anyone else who needs to do this in future, the assembly order is: shaft, brass piston, neoprene washer, hydraulic seal (open face inwards), brass plate, nut.

Now I have two working pistons, time to reassemble the whole unit and check it actually works.

[mk1]

I remember being told some years ago that when hydrolastic cars first appeared in 1962 only BMC dealerships had hydrolastic pumps, would that be correct?

I am sure that would have been the case. They weren't a cheap bit of kit either.

[BLT]

Anyone know where I can get a cap to fit the resevoir on top? Either an orginal if anyone has a 'spare', or some other type that might fit. Seems to be around 2" across and very course thread, not sure if it needs a perfect seal. Was looking at item 301663237424 on eBay, it's an IBC blanking cap for those big water tanks, but doesn't look deep enough. Any ideas? Thanks.

[rich@minispares.com]

I'm sure one from a plastic jerry can will fit

[BLT]

That's what I thought but can't find one big enough.

[iain1967s]

Seems to be around 2" across and very course thread, not sure if it needs a perfect seal.

I think the cap is just to stop dirt getting in, to protect against spills when moving the pump, and to reduce evaporation of the fluid in the tank during storage.

It does not seem to provide any kind of pressure seal, in fact mine has a 1/8" vent hole at the top to allow air in to / out of the tank so it doesn't either collapse or inflate when the pumps are used.

Not sure where you could get a replacement, but the thread looks similar to that on a petrol lawn mower or other small engine such as a snow blower or go-kart.

[iain1967s]

Well, here is the end result of my pump restoration. The new seal holds a vacuum against my finger on the Schrader, and nothing seems to be leaking out after I half filed the tank with 5 liters of green 50:50 antifreeze premix.

The pressure side still isn't working properly yet - the piston was pumping air OK before I filled the tank, but the handle is now very hard to push down since the pump was primed with fluid. I think I might have put the outlet one-way valve in backwards. Should have taken more photos during disassembly.

Note: I replaced all 15 Dowty washers with new (1/4" BSP) when reassembling, and I decided to use the repaired original tank rather than the new one.

Because of the epoxy repair to the bottom of the tank I used O-rings on both sides of the bottom outlet to give a more flexible seal with less stress on the tank than the original plastic washers.

ps. Yes, I know the white and black arms are the wrong way around, pressure should be black, vacuum should be white. It was like that when I got it, but the arms are seized on the threads currently. I didn't want to force it...

[Peter Laidler]

That's a brilliant job Iain and I've been following your progress, learning on the way. I'd like to do one one day just for interests sake really. I wonder why you don't do one of those singular '....this is how to do it' threads for the RELATED TO thinggy on the technical talk bit of the forum. There must be plenty of these old cabinets sat unused and rusty. Just wish thge owners would sell them on. To be honest, seeing your progress, it must be worth taking a punt on an old knackered one for a rebuild project!. Great work