TD5 Disco Auto Transmission hesitation / jerk

Quote:

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Originally Posted by AndrewMilne

I don't know how to check for over-boosting, but at least I know now that it could be a factor.

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If you can drive around normally & all is well,
if it only does this when you "nail" the throttle (or heavy throttle under load) then a good chance is it's over boosting, you need to wind out the thread (lengthen) the thread on the wastegate adjustment, 1 turn at a time & retest. (drive)
Mark where it's set atm, (liquid paper is handy) so if this doesn't help, put the adjuster back where it was
If you don't know what this is, you need to find someone who does.
Good luck

See here for some pictures regarding the wastegate adjustment:

http://www.aulro.com/afvb/good-oil/1...djustment.html

these problems may also be due to a dirty map sensor or oil in the ecu

Quote:

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Originally Posted by roverv8

If you can drive around normally & all is well,
if it only does this when you "nail" the throttle (or heavy throttle under load) then a good chance is it's over boosting, you need to wind out the thread (lengthen) the thread on the wastegate adjustment, 1 turn at a time & retest. (drive)
Mark where it's set atm, (liquid paper is handy) so if this doesn't help, put the adjuster back where it was
If you don't know what this is, you need to find someone who does.
Good luck

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roverv8,
That seems like something I can try myself - many thanks for such a clear indication of what to do.
Andrew

Quote:

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Originally Posted by AndrewMilne

[FONT=Calibri][SIZE=3]
Occasionally, I hear a gurgling sound from low down, up front somewhere – I think it is from the engine side of the firewall but cannot be sure. This sound occurs rarely, but it seems to happen just after hitting some kind of a bump, like a gutter in the road or just a 5cm step-up from the road to a driveway.
[FONT=Calibri][SIZE=3]Could there be a connection between the source of this sound and the transmission hesitation?

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The gurgling sound as you called it could be the traction control kicking in. Tends to happen when you accelerate over a bump in the road - especially when turning at the same time. Should see the TC symbol flash up on the dash at the same time.

DiscoDB,
Thank you for that observation.
It HAS seemed to me that the sound occurs (at least sometimes) when turning to the Right. The only other suggestion that I have had is that it is from the heater matrix behind the dash, but to me it does seem to come from further forward. Can you explain WHY it seems to happen after hitting a bump?
Does Traction Control involve hydraulic fluid, and what actually causes the sound, if it IS Traction Control? The noise reminds me of what you hear when cavitation occurs in a fluid (like when you kink a running hose).
Cheers, Andrew

PS: I haven't noticed the TC indicator light come on, but the sound does not last long and I may just not have seen it.

About that gurgling sound from the heater matrix area...it killed my nervs for almost a year and i couldn't find it's source, i've checked everything, bled the cooling system(at the bleed nipple) several times and no joy... as i have a FBH too(cos here is needed in the winter) which complicated more the coolant circuit i thought that maybe some air still got trapped in the system and the "classic" bleeding can't get it out as that gurgling came at around 3000rpm on mine and nobody bleeds the system at such revs, also the thermostat's bypass valve must open at 1500rpm but it might open later... i have a threaded hole in the coolant elbow where the temp gauge's probe is screwed in, i asked a friend with a lathe to make me a fitting for that thread, i attached a hose to the fitting long enough to direct it into the expansion tank so this way the coolant wasnt all over the engine bay while i was bleeding it and went with the car to a ride this way with the cap removed and the "bleed hose" into the tank, floored it well few times and the gurgling dissapeared...so my conclusion is that there was air trapped in the system below the bypass flow valve's circuit though(where the heater matrix is) and it gurgled when the flow became more "agressive"

as about TC, hitting a bump can always create some wheel spin then the TC kicks in cos it's supposed to put brakes on the spinning wheel/wheels of an axle ... the sound comes from the modulator where during TC action the inlet and outlet solenoid valves on both circuits are opening/closing in a fast sequence to equalise the wheel's rotation.

as your's has a "hesitation" it might be due to TC action cos then brakes are applied

Quote:

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Originally Posted by roverv8

If you can drive around normally & all is well,
if it only does this when you "nail" the throttle (or heavy throttle under load) then a good chance is it's over boosting, you need to wind out the thread (lengthen) the thread on the wastegate adjustment, 1 turn at a time & retest. (drive)
Mark where it's set atm, (liquid paper is handy) so if this doesn't help, put the adjuster back where it was
If you don't know what this is, you need to find someone who does.
Good luck

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roverv8,
I have done what you suggested, and wound out the thread adjuster on the wastegate rod by just one turn. This seems to have done the trick. I have only been for one drive since where I could safely open it up a bit, and the jerkiness seems to have gone. My wastegate adjuster has a knurled adjusting nut inside a square "buckle", so that made it easy, once the locknut was slackened off.
Many thanks!
Andrew Milne

Hi Simon,
Thanks for posting a link to annotated photos of the TD5 wastegate adjuster.
That made things pretty clear, and I have tried doing what roverv8 had suggested.
Just one turn, lengthening the wastegate rod, seems to have fixed it.
My adjuster is actually a bit different from the pictures, as it has a knurled turning nut inside a square "buckle". This makes it pretty easy once the locknut has been slackened.
Cheers, Andrew