Suspension pump

[koan]

koan, I sense I have inadvertedly offended you?

No, not at all. I must have has a bad day yesterday, I seem to have trod on toes  right, left and centre. All I can say is I was in a bit of a rush, trying to get out the door so that might have carried over in my hurried posts.

I was only pointing out that I was the original source of what you posted and it wasn't to be taken as a another party confirming what I had said in an earlier post.

koan

[s class]

OK, fair enough. 

[Big_Richard]

a scientific question now Koan,

If one was to use a slightly higher viscosity hydro oil in the suspension system to firm up the suspension and improve handling - would undue stress be put on these shaft seals resulting in them leaking? 

I have the above mentioned situation, but my pump started leaking 100x worse from the day i opened it up to change the front cover. The centre shaft got trapped in it and came out along with the cover

[koan]

If one was to use a slightly higher viscosity hydro oil in the suspension system to firm up the suspension and improve handling - would undue stress be put on these shaft seals resulting in them leaking? 

I wouldn't think so. There is only one shaft seal and it's on the suction side of the pump. The two HP o-rings are should be of a material type selected for high pressure use, have a look for NBR 90 on the web. The pressure shouldn't be any higher because of the regulator on the tank.

Interesting idea PB, higher viscosity fluid would increase damping because of greater resistance passing through the small holes in the piston. Not sure it would make the "springs" stiffer though, the way to get harder "springs" would be higher nitrogen pressure in the spheres - I think.

Worth a play though if a suitable fluid can be found.

I have the above mentioned situation, but my pump started leaking 100x worse from the day i opened it up to change the front cover. The centre shaft got trapped in it and came out along with the cover

Not quite sure what you are saying PB, you were using higher viscosity fluid ?

Did the shaft come out with the two rings or did the rings stay with the pistons?

koan

[koan]

I was on the phone getting prices on parts today and happened to (just happened to ) bring up suspension pumps with a MB parts man from way back.

He said that resealing old pumps is not always successful, they replace all o-rings and the seal but sometimes they still leak. They put the failures down to hairline cracks in the alloy body.

This is the second time I've heard that, first was when my pump still leaked after a fix. I didn't believe the hairline crack theory then but more willing to from this source.

koan

[Big_Richard]

I have indeed aftermarket hydro oil in my suspension system, its modern, its slightly more viscous, offers superior antiwear protection for metal and protects rubber in the system also. The best part of all, its a shitload cheaper.

I removed each strut and flushed it with petrol, the whole system was cleaned before hand. The spheres are new as of 2004 and still as perfect as new.

My car doesn't need to slow down to go around corners, there is no body roll and at the same time you don't feel any road undulations or even speed bumps.

I put it out there, that this "cheap mod" has made my 6.9 handle unmentionably far superior than anyone else's using genuine fluid Ask TJ for confirmation, i have taken him in this car and its f-ing ridiculous. The genuine fluid is too light resulting in boat like handling, I prefere mine.

Email me if you want to know more, Koan. 

[TJ 450]

Riding in PB's 6.9 is certainly a jaw-dropping experience.

Handling-wise, it is light years ahead of my 450... it grips and bites into those corners like there's no tomorrow.

Tim

[koan]

I've always thought 6.9s are too mushy.

After new front shocks and five spheres installed a couple of years ago I expected a great improvement in handling. The ride improved and the front no longer dropped over night but still the same body roll when cornering.

To me its the body roll that is disconcerting, doesn't inspire confidence.

I don't drive with tyres screaming for grip on every corner but every now and then a quick and unexpected deviation from straight is needed or I end up in a corner quicker than normal, it's at these times the car is a bit of a disappointment.

Anything that can help in that area is going to be a great improvement.

koan

[WGB]

The thought of thicker hydraulic oil is very appealling - wish someone had mentioned it before I changed mine with the original stuff.

My 450 always cornered very flat - much better than a 126 - and my 6.9 always powers around right hand corners even better but I am still a little unimpressed with left hand corners as it appears to roll (although much less with the front suspension rebuild - and still awaiting the rear suspension bushes).

Some of this may be more of  a perception than a reality due to the right corner of the seat squab being softer than the left.

There is also still the perception that the faster you drive a 6.9 the more responsive it becomes and I would hypothesise that maybe the pump output may have something to do with that.

Bill

[s class]

From my investigations, the pump can make the required pressure to reach the threshold of the pressure regulator even at idle. 

As to handling, I too am not real happy.  The blue car has new struts and spheres, and during my recent long trip, I had to swerve quite sharply left then right again at 120 km/h to avoid an oncoming car (illegally overtaking on a blind rise).  It was a tough and go thing - the tyres never squealed, but it felt like it took ages for the body to start following the tyres after they had changed direction.  My 280 is far sharper and more confidence inspiring in that sort of situation. 

[TJ 450]

Those are very interesting observations. I still haven't driven a 6.9 to the extent that I'm familiar with handling in those sorts of situations.

I know that my 450 is not up to scratch in the handling department... the front lower control arms need attention, although it is still pretty confident, even on unsealed roads.

It will be very interesting to experience, when I give my 6.9 its long awaited test drive out to York/Toodyay. The roads in that area are a bit of a challenge for some vehicles.

Tim

[koan]

From my investigations, the pump can make the required pressure to reach the threshold of the pressure regulator even at idle. 

Agreed and the way to check it is to hold the pump output hose. The hose vibrates on each pulse of fluid, when the regulator goes in and out of regulation the characteristic of the vibration changes. Should be able to feel the change at idle.

As to handling, I too am not real happy.  The blue car has new struts and spheres, and during my recent long trip, I had to swerve quite sharply left then right again at 120 km/h to avoid an oncoming car (illegally overtaking on a blind rise).  It was a tough and go thing - the tyres never squealed, but it felt like it took ages for the body to start following the tyres after they had changed direction

That describes it pretty well, on a quick steering change I'm never sure what's happening, too much, too little, body roll back and forth, no idea what's going on.

koan

[WGB]

As to handling, I too am not real happy.  The blue car has new struts and spheres, and during my recent long trip, I had to swerve quite sharply left then right again at 120 km/h to avoid an oncoming car (illegally overtaking on a blind rise).  It was a tough and go thing - the tyres never squealed, but it felt like it took ages for the body to start following the tyres after they had changed direction.  My 280 is far sharper and more confidence inspiring in that sort of situation. 

What's the condition of bushes and ball joints like?

Bill

[s class]

Bill, uppers have been replaced, ball joints are OK, lower control arms ideally need new bushes.  so yes, I'm sure that will improve things.  The red car needs no work in this regard, and it is a little sharper.  another difference is the blue car is shod with Michelin 205/70's and they are really terrible, marshmallow style handling with slow response.  the red car has Bridgestones that are light years better. 

[Big_Richard]

after working on my car this afternoon reassembling the front end, even removed and replaced a strut and lost a shitload of fluid in the process.

I discovered a very easy way of bleeding an air locked suspension pump, all one needs to do is put the control disk into the service position to depressurise the main valve, wait 15 seconds, and put it back to normal. Bobs your aunty.

Look forward to obtaining another suspension pump, this one is giving me the shits.