Simon's new Xantia V6 and Leaf blog

[Mandrake]

So today after driving through some roadworks I started to hear an intermittent scraping noise from the front right hub/disc, particularly noticeable at 30mph.

This is not a new noise - I've heard it a couple of times before after doing a rapid stop from high speeds when the brakes were already hot - it would make this intermittent scraping noise which would fade away over a couple of minutes. But I have never heard it before when driving casually at 30mph not doing any significant braking so I decided it was time to strip the caliper down, especially when I have suspected the front right caliper of intermittently sticking on slightly as previously discussed.

So off the caliper came and the problem was immediately apparent:



The edge of the inner half of the disc has exploded with flaky rust all the way around which has increased its diameter enough to scrape against the edge of the pad retaining bracket... Not only that but it has also been scraping against the main caliper clamp, as evidenced by the patch at the top left rubbed smooth:



I started to file the rust back around the outside edge and discovered that it fell off in chunks, so I just tapped all the loose rust off around the edge and then gave it a clean up with a file and wire brush. That half of the disc is now about 4mm smaller in diameter than the other side but its a nice clean smooth edge with no rust.

Clearly on previous occasions when the noise appeared after hard braking it was due to the disc heating up and expanding just enough to make the rust rub against the bracket, why it happened today without hard braking I'm not sure - perhaps hitting a bump in the roadworks caused some of the flaky rust to start coming away, it really was just falling off with the slightest tap when I cleaned it up...

One thing that flummoxed me today is that I noticed, as you can see in the picture above, the rubber on the piston seemed to be stretched beyond its limit with the seal lifting up away from the piston. On investigating I realised that since I had lifted the caliper up and had been working on the rust problem the piston had extended itself out about 10mm past where it had previously been - and past the normal working range of the piston judging by the rubber boot.

How this happened I have no idea - I did not press the brake pedal nor did I bump the handbrake lever arm on the caliper - which was already disconnected before I lifted the caliper up. I did pivot the caliper assembly up and down many times on its pivot while filing the rusty disc so the only thing I can think of (besides a leaky doseur valve or a collapsing brake hose) is that perhaps bending the hose back and forth pushed some fluid into the piston and moved it out... but I'm not convinced by that theory.

As I have previously suspected this caliper of sticking on sometimes naturally I'm concerned that the pressure to the caliper may not always be 100% releasing... anyone have any idea what might have pushed the caliper out ? It did not happen on the other side when I did that one. Did I bend the hose back on itself too tightly ? I wound the piston right back in and it didn't come out again so its still a bit of a mystery...

When I tried to remove the pads I discovered a likely cause of the brake sticking on and "clicking" when letting go the first use each day that I reported earlier - the "ears" on the edge of the outer pad on the front right were well and truly wedged in by corrosion in the curve that the ears sit in - even with a hammer and screwdriver against the backing plate of the pad I struggled to get the pad to let go, it looks like the edge of the pad had actually corroded fast to the pad carrier bracket. The inner pad was pretty bad as well.

Once I had the pads out I gave the mounting bracket curve and pad ears some wire brushing and a little filing to clean them up so that the pads can move in and out freely, I then added copperslip to the mounting bracket in all four locations:



I don't know if other people do this but it seemed like a good idea. After this I put the pads back and found they can move in and out freely, yet the anti-rattle spring built into the pad still keeps the pad from rattling sideways at all. Perfect. I also re-greased both slide pins with copper slip and put it back together.

I also did the left hand side to make sure there wasn't any brake imbalance - the left side wasn't too bad at all - the disc wasn't rusty in the same way and just had a little bit of roughness around the edge that needed wire brushing, and the pads were not rusted in like the other side but I cleaned the ears up and greased it in the same way all the same.

So far so good. The brakes seem nice and sensitive and there is no creaking/clicking just as you lift off the brake from stationary as before - they're completely silent and smooth in operation.

So, the mystery scraping is solved, and I suspect the intermittent light sticking of the front right may also be solved - with the pad rusted into the holder it would not have released properly. I'm still a little bit concerned about why the piston extended itself 10mm after I flipped the caliper up so I will keep an eye on things.

Although the right hand disc looked pretty bad initially (the rust made it look like the rusty half was splitting down the middle) after cleaning up both disk edges with a wire brush and file it looks very tidy now, the lips at the edge are relatively minor and there is still about 8mm of pad thickness left, so I think I'll get another 10k at least out of these discs/pads

[white exec]

Have noticed disc edge rusting over several decades. Bit of light tapping with a hammer, followed by a spin or three of the disc with a file end or screwdriver blade in position, takes it back. Can remember this happening as far back as the 70s!

Looking at the way that disc has rusted, you do wonder about how good the steel was: it has almost "delaminated" in the way that poor quality rolled steel might be expected to do. Genuine OE discs, Simon?

Good tip about copperslipping the pad ears, to ensure ease-off. XM rears have something of a reputation for momentarily sticking on after release, because they get such light use.

[Mandrake]

It's very likely they are either the original discs fitted to the car or Citroen OEM discs.

I'm only the second owner of this car with the previous owner (an elderly gentleman of 93 at the time I bought it!) owning it for the first 16 years and 65k miles and from the massive wad of carefully kept receipts I have the car was always serviced at the dealer...

I'm not sure where that wad is but if I find it I'll check for brake discs, but my hunch is they are original.

[Mandrake]

Ok ES9J4 owners, I have a little homework assignment for you.

The next few times you drive your car, try the following when starting it:

Turn the key fully on but don't start. Wait a couple of seconds then fully depress the throttle for at least a second then release it. Now start the car.

Take careful note of any change in throttle "responsiveness" during initial driving after the startup, especially light throttle pickup at lower speeds.

I've been trying this on mine and the result is quite surprising, suggesting that the ECU is not correctly self calibrating the TPS operating range without a little "help".

After a morning start, especially if I drive the car gently it often feels almost as if it is sluggish/unresponsive to the throttle or is being "held back" then after a while it will come right.

The TPS on this engine, like many is "self calibrating", where a zero/idle calibration is done every time you turn on the ignition, and a range/full throttle recalibration is done on the fly during driving when full throttle is detected, which means TPS calibration can potentially change in the middle of driving.

Depressing the throttle fully with the key on but engine stopped forces a full range calibration of the throttle for that "key on session" so that the ECU is forced to calibrate idle and full throttle immediately.

Any significant difference in throttle response during driving after doing this pre-start calibration suggests a calibration problem and perhaps a worn TPS. (The TPS has not been changed on this car)

Anyway I'd be interested to see if anyone else notices a difference doing this.

[Stickyfinger]

I will try this morning

[Mandrake]

Some 4HP20 musings for those who like a good propeller cap post.

Those with long memories will remember all the hassles I had with the gearbox in my previous Xantia V6, which eventually failed with a spun torque converter neck bearing with the probable cause being prolonged (and unrecognised at the time) overheating due to a blocked heat exchanger... Other problems included torque converter clutch shudder and poor control of the converter lockup.

Naturally when I picked up my current Xantia V6 with 65K miles on the clock (now 77K) the gearbox was foremost on my mind, especially when the 4HP20 has a bit of a reputation for dying...

In most regards the new gearbox felt a lot better to drive than the old one (I was able to compare them for about a week when I had both cars at hand before the old one was sold) and one obvious difference was how much better the torque converter torque multiplication was when accelerating from stationary - suggesting the old one either had a problem with the one way clutch on the torque converter stator or that the lockup clutch was partially engaging/dragging when it shouldn't. (Which would limit torque multiplication)

All was not a bed of roses on the new one though. I noticed a few things right from the beginning:

One was that engaging 1st gear from neutral/park always had a delay of about a second where nothing happened then it suddenly it engaged with a slight jerk as the differential backlash was taken up. At the same time engaging reverse always caused quite a good thump - I wouldn't call it a bang but it was certainly an obvious jerk/thump that the old car didn't have.

There has also always been the sense that the gearbox had an unusually large amount of backlash in the diff/driveshaft area - for example driving slowly in 1st in slow motorway crawl, every time you would ease gently between pulling to overrun and back to pulling again there would be quite a lurch and seemingly a lot of backlash being taken up. So much so that I would often put it in 2nd manual (snow) to make for a smoother driving experience when crawling along.

I'd also be careful not to accelerate too suddenly after slowing down for a roundabout as it would sometimes cause quite a thump as the backlash was taken up suddenly.

Actual gear changes were OK but I didn't feel that they were as buttery smooth as the old car when it was at its best - I would call the gear changes "perfunctory" rather than smooth - they reminded me a lot of the changes on the old 4HP14 with a freewheel design, where an up-shift when accelerating would pull the car forward with a small tug each time you changed up a gear.

I tried doing an auto-adaptive reset or two over the next 9 months but it didn't really do anything for any of the symptoms.

So about 9 months after I bought the car I booked it in for a "hot flush" with the aim of making sure the gearbox and oil was as clean as possible for longevity reasons - despite the small niggles above I felt the gearbox was still a low mileage "good-un" that probably just needed some oil changes.

In hindsight the hot flush was a bit disappointing and didn't really give the improvements I was hoping for. There was some initial improvement that lasted a few weeks but over the following year I would say the gear change quality deteriorated over what it was prior to the hot flush rather than getting better. In particular the quality of up-shifts became more "tuggy" than before to the point that there was a definite tug when changing up. I also noticed over time that the torque converter lockup started to gradually become more abrupt and seem to start locking up too soon when accelerating, thus affecting acceleration.

About a year after the hot flush (this February) I decided it was time to start doing some normal oil changes of my own - the first oil change I had done on this gearbox myself. I was not convinced that the 'experts' had used the right oil as the receipt was very vague about the grade or type of oil used, and the cost of the oil part of the bill was far, far too low for it to be LT71141, even at bulk trade prices, considering that the flushing machine would have used at least 12 litres to do the job....

From my research it's very unlikely that actual LT71141 was used - transmission rebuild companies like that don't keep large stocks of dozens of different types of oil, they keep two or three "base stocks" of oil (With standard Dexron III as the most common) and then add an additive to it as necessary to bring it close in specs to a friction modified oil such as LT71141.

For example Lubegard makes just such an additive with their "Highly Friction Modified-ATF Supplement", or their "LUBEGARD PLATINUM® High Performance ATF Protectant":

http://www.lubegard.com/~/C-110/Transmission

While I have no doubt that this more or less does work, I doubt the oil characteristics will exactly match the original specs. Anyway I decided that what was done was done and that I would gradually get rid of whatever is in it by doing a few oil changes myself using actual LT71141, and in hindsight I would probably just do three manual oil changes next time instead of a hot flush.

So in February I did an oil change and noticed a small improvement but nothing that significant - in particular the backlash symptoms and rough engagement of 1st/Reverse remained. Of course a single oil change by itself sometimes won't do a lot as you're only diluting by about 50%, sometimes it can take 2 or 3 changes to get a really significant change. (I noticed this on the old V6 - one change did nothing but the 2nd and especially 3rd change really helped)

A month or so later I tried an auto-adaptive reset and again no real improvement.

Recently I was thinking about the harsh thump into reverse that had been getting gradually worse over the last 6 months or so and it occurred to me that this might be a symptom of poor rail pressure regulation due to sticky valves in the valve blocks. When a 4HP20 is in limp mode (for example simulated by removing the gearbox ECU fuse) its normal for it to practically "bang" into reverse because the rail pressure goes up to the full 16 bars and stays there in limp mode. So I wondered if this could be the cause.

I had good success with Lubegard Red on the old V6, where it took a gearbox with severe problems and more or less walked the symptoms back by a whole year, including torque converter shudder and harsh shifting...I think without using that that box would have failed or become undrivable a lot sooner.

So about a month and probably 500 miles ago I added a bottle of Lubegard Red without doing an oil change (and checked that it wasn't overfull afterwards - the bottle is only 300mL so this wasn't an issue) and noticed a modest improvement within just day or two of driving - both to the delay when entering 1st and the shift quality. There was further gradual improvement over the following month, but it by no means cured the various issues.

Then last Sunday I thought why not do an auto-adaptive reset now that it had had time to work ? In the past a reset had not done much, but I wouldn't expect it to do much unless the mechanical hydraulic characteristics of the box had changed significantly.

WOW. After one 15 minute test drive following the reset the gearbox is transformed. The delay engaging 1st gear that has been there since I bought the car is completely gone - it instantly but smoothly engages 1st now, and the loud thump engaging reverse that used to jolt against the drive-train backlash is now more or less completely gone.

A completely unexpected change is that the "backlash" that the gearbox/driveshafts seemed to have before is no longer there - the take-up from over-run is smooth now, as is going from pulling to overrun, so motorway crawl in 1st is no longer the unpleasant experience that it was before.

Torque converter lockup transition seems much smoother now and seems to be delayed compared to before when accelerating through the gears, leading to smoother and better acceleration.

Up-shifts are considerably smoother now too without an obvious "tug" that has been there for so long and actually got worse after the hot flush. I wouldn't say the up-shifts are perfectly smooth yet, but it does encourage me to do another oil change, and I will probably add a bottle of Lubegard Red during the next change.

I find it quite remarkable that these problems can remain so long and not be fixed by a hot flush, a manual oil change, and auto-adaptive resets (on their own) also didn't help, yet one bottle of Lubegard Red followed up a few hundred miles later by an auto-adaptive reset literally seems to have transformed the gearbox and solved nearly all the niggles it seemed to have. This stuff really does work! It worked on the old V6 and it worked here too.

If I had to speculate I would say there was a particularly stubborn sticky valve in the valve block responsible for regulating the rail pressure that has finally freed itself thanks to the Lubegard, (freeing sticking valves is one of their claims) and in doing so the hydraulic characteristics of the box have changed so much that the auto-adaptive reset was necessary for the ECU to perform a "fast relearn" of those characteristics to take advantage of the change.

Before this recent improvement I genuinely though the gearbox had massive amounts of backlash in the diff / driveshaft area, but apparently not!

[lexi]

If it was Mackay in Glasgow, they do keep the LT oil. I had 20 litres off them long ago.
They may have fobbed you off mind with Dexron.........thinking you were a tourist

[CitroJim]

Pleased the Snake Oil and the auto-adaptive reset seems to have done wonders Simon

I can offer no insightfulness as my mental abilities are currently very low... I actually struggled to follow and comprehend your post this morning but I think I got the basic gist of it

All I can add is that in the past I've seen good improvements when doing a reset...

[xantia_v6]

... If I had to speculate I would say there was a particularly stubborn sticky valve in the valve block responsible for regulating the rail pressure that has finally freed itself thanks to the Lubegard, (freeing sticking valves is one of their claims) and in doing so the hydraulic characteristics of the box have changed so much that the auto-adaptive reset was necessary for the ECU to perform a "fast relearn" of those characteristics to take advantage of the change....

A alternate speculation is that the transmission behaviour had been degraded due to low line pressure caused by a restricted oil filter. The Lubegaurd may have some action that breaks-down, or shifts the particles clogging the filter, or in some way makes the filter more porous, restoring flow and pressure.

[Mandrake]

Pleased the Snake Oil and the auto-adaptive reset seems to have done wonders Simon

If it works is it snake oil though ? One of the things they claim their formulation can do is to free sticking valves - in that regard I see its use as similar to hydraflushing the hydraulic system. Yes in theory if the oil had been changed regularly that would be all that needed doing, but if it is left long enough for debris to build up its possible that crud might start jamming the valves and oil changes alone might not resolve the situation.

The detail I went into in my post was mainly to make clear the car had already had a hot flush (where it was on the flushing machine for a total of 4 hours in both forwards and reverse flow directions I was told) and had a subsequent LT71141 oil change a year later and several auto adaptive resets over a period of time and the problems with thumping into reverse, a delay entering 1st and the seeming excess backlash stubbornly persisted.

Yet just a few weeks driving after the additive and a reset and the symptoms all seem to be basically gone. Even I'm surprised by that, and I was already optimistic that it would make a difference.

A alternate speculation is that the transmission behaviour had been degraded due to low line pressure caused by a restricted oil filter. The Lubegaurd may have some action that breaks-down, or shifts the particles clogging the filter, or in some way makes the filter more porous, restoring flow and pressure.

Interesting thought, although I'm not sure that it fits the symptoms - nothing I've read about Lubegard Red suggests that it would help unblock a blocked filter, whereas they do specifically make claims regarding sticking valves. (They also talk about "non-swelling seal rejuvenation" - I'm not sure if the slide valves in the control block use o-rings but if they do this could potentially be a factor)

Remember the car has also had a 4 hour hot flush where the oil flow from the cleaning machine (connected via the banjo connection) was run both forwards and backwards repeatedly, presumably to help unblock the filter, but didn't help with these symptoms.

Also I'm not sure that low rail pressure fits the symptoms - there was never any trouble with slipping clutches, in fact it felt like the clutch overlap during gear changes was excessive (too high a pressure ?) or that the frictional coefficient of the oil was wrong. Thumping into reverse would be more consistent with excessive pressure than a low pressure.

Whatever the precise details are I'm happy about the improvement. If it has dislodged some crud from the valve block then I think it would be prudent to do another oil change in a month or two.

[white exec]

There are some products and procedures that do seem to work well - I'm thinking of DieselClean etc. and Hydraurincage - to resolve close tolerance moving part issues.
Might be interesting to dig out the MSDS sheet for Lubegard Red; it might list the ingredients (if not redacted for commercial reasons).

[Mandrake]

You mean like this ?

http://www.lubegard.com/pdfs/sds/SDS-Lu ... 02-13).pdf

or this ?

http://internationalfilters.com/wp-cont ... BEGARD.pdf

Looks like some of the contents is kept secret, not surprisingly. (Even if it wasn't I don't have the chemical knowledge to understand it )

[CitroJim]

No, you're right Simon, Snake Oil was perhaps an unfortunate choice of epithet for something you have now twice proved works and works rather well..

I now need to dream up a better name for such stuff...

[Stickyfinger]

"Proper Science Stuff" oil ?

(I quote from the BBC Lost/Fake Arts programme last night)

[CitroJim]

That sounds good Alasdair It's had the science done on it well enough by Simon