Re: hard suspension when brakes on Xantia v6 mk1

[aerodynamica]

Ur, I thought that with the car stationary it stays in SOFT mode regardless of the brake pressure. Only the accelerator quick movement can make it switch to stiff suspension at speeds less than 30km/h (?)

[CitroJim]

Ur, I thought that with the car stationary it stays in SOFT mode regardless of the brake pressure. Only the accelerator quick movement can make it switch to stiff suspension at speeds less than 30km/h (?)

Yes, that is true Graeme...

It's one of the factors that makes things hard to test. Not even a Lexia/ELIT can manually switch modes which i find was quite an oversight on the part of the Hydractive designers...

[Mandrake]

Car now rides great, no jumping, breaking fine. But when I got to the MOT station they still failed it, and pointed out to be that all was fine, but when the break pedal was depressed the car suspension went solid, which was the case.
[...]
But if anyone has any other ideas I would be very great full.

Yep - find a competent Garage!!!

What do they mean by "the suspension went solid" and how were they determining this exactly ? If they had one idiot sitting with their foot hard on the brake pedal and the other sitting in the boot bouncing up and down trying to move the rear suspension then of course it will be "solid", because the car has rear trailing arms the rear suspension cannot move when the car is stationary and the foot brake is applied. Try it!

Did they have the engine running during the test ? And by the way, since when do MOT testers "test" suspension moves up and down while the foot brake is applied ? What kind of test is this ?? 25 years taking cars for MOT's and I've never heard of this ??

[Mandrake]

Ur, I thought that with the car stationary it stays in SOFT mode regardless of the brake pressure. Only the accelerator quick movement can make it switch to stiff suspension at speeds less than 30km/h (?)

You're right - pressing the brake pedal will not switch to hard mode when the car is stationary - even on a Series 1, which has a front brake pressure switch feeding into the Hydractive ECU. A slight tap of the throttle will put it into hard mode for 3.5 seconds though...

However, if the engine was stopped and they were sitting there pumping the brake pedal like idiots that would quickly use up the stored pressure in the accumulator and inadvertently cause the front suspension (and eventually the rear) to go into hard mode due to lack of main system pressure.

However if they were testing the suspension stiffness with the engine not running, they're idiots for that too...

[xantos]

If they had one idiot sitting with their foot hard on the brake pedal and the other sitting in the boot bouncing up and down trying to move the rear suspension then of course it will be "solid", because the car has rear trailing arms the rear suspension cannot move when the car is stationary and the foot brake is applied. Try it!

However, if the engine was stopped and they were sitting there pumping the brake pedal like idiots that would quickly use up the stored pressure in the accumulator and inadvertently cause the front suspension (and eventually the rear) to go into hard mode due to lack of main system pressure.

However if they were testing the suspension stiffness with the engine not running, they're idiots for that too...

[CitroJim]

Yes, those MoT testers definitely do not appear to be the sharpest knives in the block....

[rolyh]

Thanks all,
Has anybod tried; with help of a second person, pressing the foot break and checking the suspension for movement at he same time, to see if it goes into sport(firm) mode in this condition; this is with the car stationary?
I have actually contacted Citroen direct; and they don't have an answer.

[Mandrake]

Thanks all,
Has anybod tried; with help of a second person, pressing the foot break and checking the suspension for movement at he same time, to see if it goes into sport(firm) mode in this condition; this is with the car stationary?

I think I explained this pretty well in my post - no, pressing the brake pedal while stationary does not put the suspension into hard mode.

It will however "lock" the rear suspension arm's thus making the rear suspension appear to go rigid. This is completely normal and certainly not cause for an MOT failure!

[CitroJim]

It will however "lock" the rear suspension arm's thus making the rear suspension appear to go rigid. This is completely normal and certainly not cause for an MOT failure!

Precisely!

[chinkostu]

A thought, if they've got it going fast enough on the brake tester it could kick hard mode on!

[jgra1]

I haven't heard of testing the suspension and brakes at the same time either - except on the bikes, when they need to apply the brake TO test the suspension.. (if they haven't rollers)

[rolyh]

Thank all,
It appears that this is the correct function of the car, as with the brakes on the trailing up in the suspension is ridged.
As well explained by Mandrake. Thank you Rolyh

,

[chinkostu]

Probably worth finding a better tester and complaining to VOSA

[Zelandeth]

It's always annoying when you run into testers that are stumped by anything a bit odd.

Took me no end of arguing to get my Lada Niva through the test because of "excessive free play in the steering system." Yes, there's about a 1" dead zone at straight ahead. On a car with worm and pinion steering that is totally normal, and the numbers are right there in the test manual (up to 2" steering wheel movement is acceptable) for that. Must have taken me about an hour to get that sorted. Went back to my usual garage the year after!

Odd one I remember from one year though was nearly getting a fail apparently because of a defective steering lock. First off, how is that even a safety item that should even be tested? Secondly, Saab 900s don't *have* a steering lock! That was one of the big chains which I generally wouldn't let my car near as well had it not been necessary due to time. Got it sorted in the end but it made me scratch my head...

There's an awful lot to be said for having a garage you trust.

For MOTs your Local Council testing centre is usually a good bet, they're involved with testing taxis and all the Council's own vehicles (which VOSA *do* delight in spot checking) but don't do any repair work, so their incentive is to be thorough enough but they won't be looking for a reason to fail you. Never gone this route myself, but know several people who have and have all been happy.

[BenC5HDi]

I use a place that only does MOT tests and no repairs near here. They're great, and will even take me under the car and show me what and why it's failed, or tell me exactly what is an advisory and why.

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