Boot rattle - tailgate hydraulic struts?

[trixtrains]

My Yeti developed a rattle that sounds like it's coming from the boot area. Took it to the dealer who temporarily removed the tailgate hydraulic struts - drove round the block and the rattle was gone. He said another Yeti had the same problem that was cured by fitting new struts. Dealer ordered and fitted new struts to my Yeti ... but rattle still present! I'm wondering if the strut is rattling against the bodywork when the tailgate is closed. Dealer says bring car back for investigation, which I'll do in a couple of weeks. Anyone else had similar diagnosis?      

[Kenny R]

Are the rear seat belt buckles in their storage clip on the wheel arch? If not they can make a terrible rattle.

[Ryeman]

Mine has a rattle when the centre rear seat is up but not when the backrest is down.

[yetiscot]

Mine had a quiet knocking sound especially over rough roads caused by the hatch lid lock going out of adjustment. I moved the keep forward a bit[ torx needed]  The sound has now gone but the boot lid needs a firm push to close.I seem to remember when the car was new it needed a firm shove.

Try shutting the lid, then getting hold of it and shake! You will hear the sound of the rattle if that is the problem--don't hold the handle cos the door will open!

[trixtrains]

Are the rear seat belt buckles in their storage clip on the wheel arch? If not they can make a terrible rattle.

Yes, and I've removed spare wheel, boot cover, rear seats, hooks - everything - and the garage and I concluded it was the struts that make the rattle.

My next trick is to put some spongey pipe lagging around the strut so that it's held tight when the boot is closed.

Next time I go for a drive I'll see if it cures the rattle. Funny the things you get up to with a new car! 

[RickT]

When the struts are fully compressed they don't exert any force to extend and because the ends of the struts are a sloppy fit on the pivots it is this that causes the rattling.

You can see this if you open your tailgate fully and then lift it up a bit more it will lift about 3/4" higher.

When the tailgate is shut the struts are quite clear and don't touch anything else.  

 

I think changing them is a red herring unless the end fittings are a different size and thus a tighter fit. 

 

On things like this I have sprayed some Chain Lube (what I use on my motorbike) into the pivots, This stuff is very searching and then when the solvent evaporates it leaves the heavy waxy sticky grease behind and will stop the loose metal parts rattling.  Worth a try at least.

[aerofurb]

I eventually tracked down and cured a rattle at the back of TIBET III by adjusting the tailgate stops mounted on each side of the tailgate. Slip off the plastic covers, Torx screws loosened to adjust the stops down one click and retorque the Torx, fit the covers back on and total silence ever since.

[speedsport]

The persistent rattle on my Yeti turned out to the the number plate rattling against the body! I could have sworn it was something inside the car, so it took ages to trace.

A couple of self adhesive foam pads stuck to the back of the plate (not the car body) was the cure.

[trixtrains]

Thank you RickT and aerofurb, I'll try your suggestions. And speedsport: my number plate is firmly fixed. Happy Christmas to all. 

[trixtrains]

UPDATE. Yeti was booked in for its first service so the garage looked again at the rattle problem. Touch wood, it seems to have been cured. It was a loose wiring loom (I assume inside the tailgate).

[Urrell]

When the struts are fully compressed they don't exert any force to extend

As a safety note I must point out that is when they have the most force trying to extend that's how they work, fully compressed they have the most pressure gas in them.

It seems that way if you don't understand how they work only because the leverage on the strut when boot lid when very nearly closed is pushing up and down not at an angle to raise the door.

[RickT]

As a safety note I agree these things are very powerful and must not be messed with!

When fully compressed their power is stored until the strut starts to extend the power is released by heat and pressure differentials of the gas.

If one of these is fully compressed and held there it will stay compressed but soon as it is pulled then it will fully extend with full force. 

 

This link may help what I was trying to explain. Gas struts are not like a compressed bike pump or normal springs.

 

http://www.explainthatstuff.com/gassprings.html

[Urrell]

 

When fully compressed their power is stored until the strut starts to extend the power is released by heat and pressure differentials of the gas.

If one of these is fully compressed and held there it will stay compressed but soon as it is pulled then it will fully extend with full force. 

 

This link may help what I was trying to explain. Gas struts are not like a compressed bike pump or normal springs.

 

They are exactly like a compressed bike pump but due to the geometry of their mounting to the tailgate they will not push the door up much from the closed position so giving the impression of no power when closed.

The pressure is stored within and there is no magic holding it there until the door moves.

[trixtrains]

UPDATE. Yeti was booked in for its first service so the garage looked again at the rattle problem. Touch wood, it seems to have been cured. It was a loose wiring loom (I assume inside the tailgate).

Not cured unfortunately. Still rattles on bumpy side streets at around 25mph.

[Ryeman]

Could it be a loose loom in the rear pillar instead?

[ejstubbs]

They are exactly like a compressed bike pump

 

Not according to the link RickT provided.  As that web page explains, in a gas strut there are holes which allow the gas to flow past the piston, equalising the pressure on either side.  It's the different surface areas of the two sides of the piston which creates the force: same pressure acting on two different surface areas -> two different forces, proportional to the different surface areas.  If the forces are 180 degrees opposed then there will be a net force in the direction of the larger one.

 

the power is released by heat and pressure differentials of the gas

 

Err, no.  The link you posted explains how it works.  It's not due to pressure differentials, and any heat that builds up as the gas in the strut is compressed (by the piston shaft, not the piston face) as the tailgate door is closed will likely have dissipated completely by the time the door is opened again.

Edited 1 May, 2015 by ejstubbs

[Urrell]

Not according to the link RickT provided.  As that web page explains, in a gas strut there are holes which allow the gas to flow past the piston, equalising the pressure on either side.  It's the different surface areas of the two sides of the piston which creates the force: same pressure acting on two different surface areas -> two different forces, proportional to the different surface areas.  If the forces are 180 degrees opposed then there will be a net force in the direction of the larger one.

It operates exactly like a "high pressure" pump operating on rod displacement compressing the gas and will have its greatest force pushing out when most compressed.

There is no magic holding it closed just the geometry of the fixings providing no lift to the tailgate until the geometry changes as the tailgate is opened.

[AlanReed]

I too have noticed a rattle from the boot lid area and also think it's coming from the gas-struts. My very un-technical temporary fix is to jamb two washing up scourer sponges into the recess down the bodywork recess, so it stops the gas struts from rattling when the boot lid is closed. This seems to have stopped the rattle. My Yeti is about 15 months old, so I'll be contacting the dealer to seek advice..... 

[Urrell]

I too have noticed a rattle from the boot lid area and also think it's coming from the gas-struts.

I doubt it's the gas struts rattling as they are under great pressure when the boot is closed.

 

Have you adjusted the rear hatch stops either side towards the bottom of the door, that may need doing to stop the rattle.

This on the other Forum shows how to do it, 8th post down.

http://www.yetiownersclub.co.uk/forum/boot-lock-not-working_topic2356_page2.html

Edited 15 August, 2016 by Urrell