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Mar 12, 2023 18:54:06 GMT
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I'm having trouble with my broken W202 that I bought off Facebook Marketplace to cover the broken car I bought off Facebook Marketplace to cover the broken car I bought off Facebook Marketplace in that it only stays in low gear (ie 2nd) and doesn't change up.
There is a lot of clicking from the shifter mechanism - it won't go into P/R unless I take my foot OFF the brake pedal. I thought this was the other way round? It did this once before when I was coming back from Newcastle (380 mile round journey), but fixed itself. The clicking sounds like the lock mechanism, but not seen it yet.
I've changed the battery, it's not that. I've checked the brake switch - it looks OK, but I hear these are troublesome for some reason, even though it's just a bunch of contacts in a two pole switch. I'm thinking it could be this, even though the brake lights work, but the whole thing above points to this.
I've also drained the transmission fluid which didn't look as fresh as it was, but intend to change that and the fluid anyway.
There's a lot of information with a variety of faults on the internet, but none of it has a conclusion over whether it was fixed or not.
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Last Edit: Mar 12, 2023 18:54:51 GMT by davidbb
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Mar 13, 2023 17:33:14 GMT
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I changed the transmission fluid and changed the filter (8 litres and not cheap). Still the same. I took the selector off - I had a look inside but there's not a lot of circuitry apart from a potentiometer for the gear stick and an optical/magnetic sensor for the W/S button. I went up to the local MB specialist who said it might be the speed sensor in the gearbox, or the shifter mechanism. 600 - 800 to change with a second hand unit.  |
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Mar 13, 2023 22:01:20 GMT
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The first thing to do is read the OBD fault codes. A great starting point, if nothing more. I'd also advise you find a different Merc specialist.
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Last Edit: Mar 13, 2023 22:02:25 GMT by Woofwoof
Still learning...still spending...still breaking things!
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I only went up there hoping he would give me some free advice - it takes 10 minutes to swap the shifter over fortunately, it's not difficult.
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Mar 18, 2023 12:23:43 GMT
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First cheapest way to fix this is to replace the valve body. If that doesn't work replace the whole box. Buy a cheap box off eBay. Change the valve body with it in the car. If no better change the whole box.
An idea for what could be causing it is the solenoids. They are the little electromechanical valves on the valve body which open and close to allow fluid to pass from one part to the other and cause the actuation of the clutches which engages and disengages different gears.
If the solenoids are broken or dirty it will prevent gear changes as they literally control whether or not a gear change will be attempted.
You can rule out major components like the torque converter, oil pump and other major chunky pieces of metal because it works up to 2nd gear. If there was no slipping prior to losing 3rd-upwards then it's not burnt out clutches.
Aside from broken or blocked solenoids some part of the fluid canals could be cracked or a seal perished and that would have the effect of bleeding the fluid away losing pressure and stopping the change.
If the fluid is black then clutches have burnt out and the whole trans will have to come out. But the easiest repair is to chuck in another valve body and see if you're lucky. It's a gamble.
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Mar 18, 2023 12:35:07 GMT
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The first thing to do is read the OBD fault codes. A great starting point, if nothing more. I'd also advise you find a different Merc specialist. This definitely should be the first move. Staying in 2nd or 3rd gear is typical “limp home” strategy and can indicate anything from low oil level to failed clutch packs. |
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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Mar 18, 2023 12:51:37 GMT
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Considering what these were like for brake light switch problems from a very early age and what you said about taking your foot off the pedal to select P/R, I'd at least give one a try.
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'57 Austin Cambridge A55 1800 Overdrive
'50 MG Y-type (In build)
'56 Standard Super 10 (In build)
'03 Fiat Stilo Abarth (Wet weather runabout)
'03 Citroen Berlingo HDi (Parts hauler)
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pow
Part of things
Posts: 110 
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Mar 25, 2023 10:04:01 GMT
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Kinda unrelated but maybe relevant - in 2016 I drove a 207cc auto across to Austria. Moved most of the way, when I stopped for the first time in 300 mines in Austra it decided it didn't want to select first gear any more (box full of neutrals) which started the entertainment of either trying not to stop every time we needed to stop or quickly stopping, ramming it into N, turning the engine off and then turning it back on and throwing it into D.
The prospect of it being recovered home while it was kind of driveable wasn't one I wanted to face so after working out the hacks to keep it going we continued our trip. Sat in a campsite in southern Germany one morning warming up in the car after a cold night I could hear the shifter lock pin firing in and out quickly and lots of times. Putting my foot on the brake also caused it to work as expected and bridging the brake light switch with a paperclip also made it work as expected so ruled out the brake light switch. Once home I purchased all the completely legal DiagBox software off eBay and it was a single ABS sensor reporting the car was moving that was causing the whole thing. One new sensor and it was good as gold again.
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