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 Post subject: hydrolastic problem
PostPosted: Tue Sep 12, 2017 9:39 pm 
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848cc
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Joined: Sun Nov 18, 2007 10:57 am
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Location: Adelaide SA
Hi all
dragged the 1967 S out from the back of the shed over the weekend for the first time in many many years to try and get it on the road and take it for a spin for its 50th birthday. The first challenge was to pump up the suspension and see if that would hold pressure , it has been sitting very low for many years.
I have pumped up both sides to about 230 psi and it seems to hold pressure but the problem I have is the back has lifted quite high but the front is still sitting on the bump stops. I can lift the front up a couple of inches by lifting on the nudge bar and the rear squats down a bit but as soon as I let go of the front it goes down to the bump stops.
To the best of my knowledge nothing has been disconnected or changed but has just gone down over a long period of time and been down for many years
Hoping somebody might have an answer

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 Post subject: Re: hydrolastic problem
PostPosted: Tue Sep 12, 2017 10:00 pm 
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Location: near Baulkham Hills, NSW
I would give it more pressure, 230 is low. If the front is still way low, consider putting a 4mm washer on the front knuckle joints.
It is normal for hydro to be higher at back, particularly so if tanks are empty.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank @7000+, 45 Dellorto, RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. Going harder with Stealth Black Box in.:mrgreen:

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 Post subject: Re: hydrolastic problem
PostPosted: Tue Sep 12, 2017 10:10 pm 
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1275cc
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Joined: Fri May 02, 2008 3:07 pm
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Location: Bundy
You will find the rear lifts up first and then as the rear springs take up the tension the front will come off the bump stops. This will start to happen around 250psi. Take it up to 275psi or 280psi and then go for a drive. You should be able to get 4 fingers between the rear tyres and guards. 3 fingers between front tyres and guards.

Here is the guide from the manual.

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 Post subject: Re: hydrolastic problem
PostPosted: Tue Sep 12, 2017 10:30 pm 
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848cc
848cc

Joined: Sun Nov 18, 2007 10:57 am
Posts: 165
Location: Adelaide SA
Thanks for the replies
I will pump it up some more tomorrow and see how it goes at 275 psi
The rear is nearly at 3 fingers already

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 Post subject: Re: hydrolastic problem
PostPosted: Wed Sep 13, 2017 6:59 am 
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1098cc
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Joined: Sat Jul 23, 2011 8:17 am
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Location: san remo nsw
A bag or two of cement in boot. :-)
As said, pump it up and if possible, take it for a bit of a drive. Old displacers new a massage if left squashed for extended period.


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 Post subject: Re: hydrolastic problem
PostPosted: Wed Sep 13, 2017 4:02 pm 
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998cc
998cc

Joined: Sat Feb 09, 2013 5:44 pm
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Location: Camden
Leyland Special Tuning booklet quotes not to exceed 300 lb/sq.in and not under 220 lb/sq.in. which will be close to bump stops. "It does not matter if the pressures are uneven from side to side."
My minis run between 275 and 280psi like gtogreen said. Ride height will vary summer/winter with temp changes, too.


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 Post subject: Re: hydrolastic problem
PostPosted: Thu Sep 14, 2017 6:31 am 
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848cc
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Location: Sunshine Coast, QLD
The front might be full of air and thus not pumping up
I would be emptying out the system then vacuum it before refilling with new fluid
A vacuum will draw the fluid forward into the front bag

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 Post subject: Re: hydrolastic problem
PostPosted: Thu Sep 14, 2017 11:11 am 
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998cc
998cc

Joined: Sat Feb 09, 2013 5:44 pm
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Location: Camden
I have never found any evidence of air in the lines affecting the ride height. Using the vacuum side of hydrolastic pump does not remove air from the system. It is used to collapse the displacers to allow you to remove struts etc. When you release the vacuum coupling air will be drawn into the system anyway.
If you pump each side up to around 300 psi, then quickly drain and refill several times, that seems to be enough to get everything working.
Drmini's suggestion about the spacer washer can also be considered if the front is too low - most hydro minis are old enough to need them now.


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 Post subject: Re: hydrolastic problem
PostPosted: Thu Sep 14, 2017 12:34 pm 
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Back in the 60s my local BMC dealer never used the vacuum side during a regular pump up. The most they did was blow it down once as Bill says.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank @7000+, 45 Dellorto, RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. Going harder with Stealth Black Box in.:mrgreen:

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 Post subject: Re: hydrolastic problem
PostPosted: Thu Sep 14, 2017 9:37 pm 
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848cc
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Joined: Sun Nov 18, 2007 10:57 am
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Location: Adelaide SA
well I pumped it up to 275 psi and the front did lift some but the back is still to high. Probably about about 4 1/2 fingers at the back and 1 1/2 at the front. I have to do a fair bit of work to it before I can drive it - all hydraulics , water pump and cooling system and fuel system clean out .I will leave it pressurised while I do these jobs and maybe take it for a spin if all goes well and then look at dr minis suggestion of spacers in the front and dumping the fluid once or twice. Wish me luck .
cheers


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 Post subject: Re: hydrolastic problem
PostPosted: Thu Sep 14, 2017 10:48 pm 
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848cc
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Joined: Thu May 11, 2017 9:23 pm
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Location: Hobart, TAS
My mini had been off the road for 40 years, I decided on 17 bar as a conservative pressure (about 245pdi).

What I have found is I get similar results as you have if I pump it up with the weight of the car resting on the suspension, after a little drive it settles itself out. When I first pumped it up, I had the car on jack stands and it naturally wanted to sit more level when I first put it back in the ground.


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 Post subject: Re: hydrolastic problem
PostPosted: Fri Sep 15, 2017 6:22 am 
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848cc
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Location: Sunshine Coast, QLD
Bill B wrote:
I have never found any evidence of air in the lines affecting the ride height. Using the vacuum side of hydrolastic pump does not remove air from the system. It is used to collapse the displacers to allow you to remove struts etc. When you release the vacuum coupling air will be drawn into the system anyway.
If you pump each side up to around 300 psi, then quickly drain and refill several times, that seems to be enough to get everything working.
Drmini's suggestion about the spacer washer can also be considered if the front is too low - most hydro minis are old enough to need them now.


I will have to disagree. So why do they vacuum out air conditioning systems. To remove the air. Why do you bleed your brakes. to remove the air.
When you vacuum out your suspension you remove the air. the setup i have allows me to change from vacuum to fluid with no disconnection.
Do the job like the factory asks and you will be OK

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 Post subject: Re: hydrolastic problem
PostPosted: Fri Sep 15, 2017 6:24 am 
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848cc
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Location: Sunshine Coast, QLD
drmini in aust wrote:
Back in the 60s my local BMC dealer never used the vacuum side during a regular pump up. The most they did was blow it down once as Bill says.


If they were just pumping it up a little there would be no need to vacuum it
If you just replaced a line or bag then you need to reinstate the system properly
You local dealer and many others were probably just lazy if they didnt vacuum the system after major work

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 Post subject: Re: hydrolastic problem
PostPosted: Fri Sep 15, 2017 7:26 am 
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848cc
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Location: Brandy Hill, NSW
Is it possible that one or more hydro bags have been replaced and that is why there is a difference?

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 Post subject: Re: hydrolastic problem
PostPosted: Fri Sep 15, 2017 8:45 am 
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They all tend to get lower at front as they age. It's where all the weight is.
My Matic sits pretty level because years ago it got a GT front subframe and bags. Rears are still stock.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank @7000+, 45 Dellorto, RE282 sprint cam, 1.5 rockers, 11.0:1 C/R. Going harder with Stealth Black Box in.:mrgreen:

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