Hydrolastic suspension questions

[jakethepeg]

I have finished my 1965 Cooper S lookalike, and the car sits with a nose down stance. I know when the suspension is leaking it usually goes down on one side. There are no leaks visible,( it was pressurised to the correct pressure about 10 months ago) and no sign of damage to the displacers when fitted Any ideas, or will it ride up with wear when i start to use it?

GEDC0018.JPG

[111Robin]

The rear suspension height should be greater than the front, the factory settings are as follows (wheel centre to wing edge) :

Front : 12 5/8" +/- 1/4"
Rear : 13 1/8" +/- 1/4"

20201230_115347 by Robin Derrick, on Flickr

[jakethepeg]

Mine looks a bit more extreme than that, but I will measure it later today, thanks

[Peter Laidler]

Ah, Jake, hydro suspension. Great looking car by the way. Hydro is my pet hate but one that I've made it my business to learn about explore at some depth. First thing, relating to your car is this. The car WILL settle after a rebuild or after you've blown it up again. The next thing is, assuming that it it all mechanically correctly assembled, to inflate the suspension. Forget about pressures etc etc and inflate the suspension with clean, new hydro fluid UNTIL THE FRONT DRIVE SHAFTS ARE PARALLEL to the ground. This is the optimum mechanical setting for YOUR car as opposed to the handbook which caters for everything. The rear WILL be higher now but the pre-set helper springs will be pulling he rear downwards. Roll the car back and forth a few feet to allow the front wheels to resume their natural tendency and have a final check. Inflate to adjust

Use car, after a week check again. Adjust as necessary and drive off into the sunset!

Hydro seems to frighten the cra....., er...... willies out of some. Don't let it frighten you Jake!

[Spider]

Hydro, like Dry Suspension still retains Rubber as a Spring and I've found like Dry Suspension it does sag over time, but being Hydro, the part with the heaviest weight will sag down and push the back up. The Helper Springs certainly do help, but don't stop this occurring.

With most cars you can swap front and rear bags. Another option is when parking up, jack up the front to get the wight off it and on to the rear wheels.

Totally agree with Pete, forget the Pressures, work from heights.

[Daz1968]

When I rebuilt my Cooper I fitted shock absorbers on the front and competition bump stops all round, also good rear helper springs, seems to make it sit a bit better, I did also fit some units on the front I had from a spare rear frame. But this was done because the hose connectors on my front ones were more corroded than the spares I had. I also believe it it wasn’t vacuumed properly air can remain in system at front and it compresses where the fluid doesn’t.

[mab01uk]

There are two types of rear Helper Spring, have you got the right type fitted?
Minimail:-
HELPER SPRING - HYDROLASTIC . PRE 1966 . S/H £15.00 U.21A1566
HELPER SPRING - HYDROLASTIC . REAR 1966 ON . S/H £15.00 U.21A1806
https://www.minimail.co.uk/parts/

Quote from Peter in thread below:
"It is the actual weaker HELPERS that caused the nose to droop. The later strongers pull the rear downwards"
http://mk1-forum.net/viewtopic.php?f=3&t=26697

[Peter Laidler]

Mab/Martin is absolutely correct about the helper springs. 1)Early SHORT spring with LONG link rod. 2) Later LONG spring with SHORT link rod.

In answer to Daz, he's right too. You can easily compress any air in the system. But any air remaining in the system ALWAYS migrates to the highest point - it's the laws of fizziks inn'i - and that point is the highest point of the front hoses. But help is at hand and there is a simple cure.
1) Depressurise the system safely using the ultra simple hose and push-rod thinggy illustrated in an earlier thread).
2) Save the fliud (there'll be half a pop bottle from each side), allow it to separate for an hour or two and syphon off the clean rust free fluid at the top. You an then filter this clean fluid through a couple of coffee filters. If you have the facility test fluid for SG
3) Unscrew the front hose from the adaptor - that's very probably full of rust and crap, but that's another matter - and stand hose up.
4) Fill hose and hydro unit with fresh fluid. Leave to settle and re-fill as required.
5) grease threads, put finger over end of hose and quickly place hose back onto adaptor with absolutely minimal loss of fluid and tighten up
6) Simplicity itself
Pete the Pom

Added later: Swopping the bags from front to rear as suggested by Spider is a good idea but you've got to take the suspension right down for that. But, even so, don't let it frighten you. And NEVER forget that at the front, the hose to unit joint is upright and sat within a 1.5" deep dish and ALWAYS immersed in water that cannot escape. Corroding the steel hose clamp. Drill a 1/4" dia vent/escape hole if the unit is removed as illustrated in a previous thread/tech article.

Hydrolastic......, my pet hate. To be honest, mechanically I think...... Best say no more

[Aussie Bill B]

There are two types of rear Helper Spring, have you got the right type fitted?
Minimail:-
HELPER SPRING - HYDROLASTIC . PRE 1966 . S/H £15.00 U.21A1566
HELPER SPRING - HYDROLASTIC . REAR 1966 ON . S/H £15.00 U.21A1806
https://www.minimail.co.uk/parts/

Quote from Peter in thread below:
"It is the actual weaker HELPERS that caused the nose to droop. The later strongers pull the rear downwards"
http://mk1-forum.net/viewtopic.php?f=3&t=26697

As well as different helper springs, the struts were also changed at the same time: pre '66 were 9 3/8" ; post '66 were 9 3/4".
I have a similar rear height issue with an early S where I fitted later struts, not realising they were longer. Planning to fit adjustable struts in the near future.

[Dr S]

Has it all been apart? I’ve found they can take some Persuasion back to level. Later spaced knuckles up front can help. As can a few cycles of the system pressure to atmosphere to ‘burp’ it.
I have a similar stance to you. Chucking the steelies on when at full droop seemed to help as you can’t get full droop any more with that stance.

[mk1]

As has already been said, Hydro cars are supposed to be nose down.

[IAIN]

This is my car which I built last year, it's covered about 400 miles. I was concerned when building it, that I might have a problem getting it to sit as I wanted. I hate the nose down stance. When I pumped it up, it sat level and so far has stayed that way, which I was more than pleased with.
It has competition bump stops and shock absorbers on the front, the rear is standard. So they can, sit level, but no idea how.

[111Robin]

The tolerance on the factory settings can result in the rear being 1" higher than the front. Might look odd but perfectly "standard". Looks like you've been lucky Iain, I still can't get mine to sit level across the car, it's either level at the front or the rear, impossible to get it on both.

[Maddog]

To get my Australian 66 S to sit level I ended up using 10mm (3/8") spacers on the front knuckles and swapped out the early rear hydro helper springs for a late Australian (Leyland) set - much stiffer. That helped to level things up a lot. Competition bump stops and Konis on the front was probably overkill but it did feel much better. The displacers were the early S yellow band type.

[111Robin]

Some gold bullion in the boot will probably work, or blue circle as a cheaper option.

[seandoyle]

I’ve got a mk 2 with hydro. Standard shocks on front & comp bump stops all around . Front feels good, reasonably firm but the rear is very soft,offering hardly any damping. Is this normal ? Wondered if modifying the rear arms to take shocks is worth considering .

[Peter Laidler]

I'm sure you know my views on putting shocks on a hydro car Sean. I'll put my head above the parapet again, steel helmet on awaiting the incoming mortars and say that if you've got correctly set up hydro on a typical road car, then you've already GOT shocks, built in! That's what the 'hydro' part of hydrolastic is. But to answer the interesting hydro Q you ask, I'm not sure that putting shocks on the rear will cure anything because the hydro helper springs are constantly holding the rear DOWNWARDS....., something that the shockers wouldn't be doing.

I'm minded to suggest that you've got something in the rear part of the system that is making it bouncy......, something compressible......., something that reasserts itself PDQ....., something like air! Any air in the system usually migrates slowly to the loop in the top of the front hose. But once it is caught in a hydro bag, it's a bugger to get rid of

Before you spend out, what about evacuating the hydro system, flushing it fully and then refilling. A process of elimination could......... Nope, I'll leave that for later.

[bwaminispeed]

The valves inside the Hydrobags, are probably long gone rusted away, most are......This causes the bouncy ride you are feeling.....

Putting a restrictor in the lines, helps quite a bit, even though, there is no actual valving type action.....Having an adjustable valve for the restrictor (still no valving action like the built in Hydro valves) will enable you to tune how much bounce you get.......

[seandoyle]

Thanks for both reply’s. Air will be a factor no doubt & I have tried to expel as much as possible. The car ,in my opinion feels as suggested,that the valves have indeed rusted away. It feels as if no control/shock absorber is happening.I have the option of changing the rear displacer’s which I’ll do .Im interested in fitting an in line vale,so any suggestions on how to do this would be appreciated

[Peter Laidler]

PM sent Sean but look before you leap.