Citroen XM Forum

My mechanic has advised that the stuck valve issue was more common on the HP14 box but the block is certainly worth a look. With regards, Matthew T.

Hi Dean,
My apologies for the further bother, but I just wondered if you have any photos of the valve block to show the sequence of stripping down around the 3-4 and 4-3 valves? After removing the side cover plate on my spare block the main components accessible are the springs and I am unsure how to reach the actual valves. I might be tempted to investigate checking and freeing the valves if that is my problem, rather than replacing the block!!
With regards,
Matthew T.

Another guide for you Matthew. http://www.matthijsjansen.eu/Citroen_XM ... erhaul.pdf

AFAIK, the valves just follow the springs out of the body.

The hydraulic circuit diagrams in the ATSG manual linked to previously indicates loss of forward drive should be that valve. The only other items I can think of would be a mechanicl failure of the 1st or 2nd one way clutches, or the gear selector cable being incorrectly set.
Looking at the clutch and band application chart on page 8, it shows that failure of the Forward Clutch will result in loss of Forward drive, but leave reverse.

I would get familiar with how these boxes work by stripping one down, as it seems that rebuilds are rarely successful first time round.

I have grown to dismiss entirely the gear selector cable adjustment in solving problems, there is no fault gear selector cable adjustment can cause other than the inability to select gears at each end of the selector mechanism, namely, P and 1st and more commonly a no crank problem when trying to start. The entire mechanism including the detents that you feel when moving from gear to gear are within the box itself.

Here are the valve block retaining bolts
CIMG3290 by Deanxm, on Flickr
Here is one of my reference photo's of the block with the spring retainer plates removed and the sections to remove to gain access.
CIMG3260 by Deanxm, on Flickr
CIMG3257 by Deanxm, on Flickr

If i remember correctly this was my 'education valve block' which i did a dummy run on before cracking open my boxes own block to find a broken shift sequencing valve spring broken.

Previous guides posted above do not look like 4HP18 ones even though it says they are, could be the RWD version of the box? i dont know but i think from memory the traction valves you are after are on the top deck, the lower deck is damper valves and pressure regulators but i would have to look back through the manual to confirm that.

I found carefully going over the valves and bores themselves with a super fine emery paper and then a thorough clean of that section of the valve block before putting it back together cures the issue of sticking, provided the bores are not unduly worn. Do not attempt this emery method on the bore unless cleaning of the spool valve alone will not result in smooth movement and ensure you have that section of the block removed so it can be thoroughly cleaned after without risk of contamination to the rest of the valve block.

You dont want to get it dirty in here
CIMG3252 by Deanxm, on Flickr

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MTXM wrote: ↑

Mon Feb 11, 2019 7:55 pm

My mechanic has advised that the stuck valve issue was more common on the HP14 box but the block is certainly worth a look. With regards, Matthew T.

It is also very common on the HP18 Matthew, don't take my word for it, search the Saab 9000 forums, there are plenty of people on there who have had a loss of fwd drive and have stripped the valve block only to find the 3-4 or 4-3 valves sticking.

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MTXM wrote: ↑

Mon Feb 11, 2019 9:34 pm

Hi Dean,
My apologies for the further bother, but I just wondered if you have any photos of the valve block to show the sequence of stripping down around the 3-4 and 4-3 valves? After removing the side cover plate on my spare block the main components accessible are the springs and I am unsure how to reach the actual valves. I might be tempted to investigate checking and freeing the valves if that is my problem, rather than replacing the block!!
With regards,
Matthew T.

As Will says they should be extractable after removing the spring retainer plate, don't practice on your known good valve block if it's from a V6, better to fiddle with the suspect unit to get your eye in. My memory is hazy on this, it isn't great at the best of times and it was a good few years ago now, many projects have come and gone since.

D

Well chaps, I now have the valve block off and stripped as far as I dare! The spring retainer plates are removed on both sides and all loose parts extracted as my last photo shows. The end 4-3 traction valve certainly did not appear to be stuck but the 3-4 valve cannot be removed at this stage and also will not press in, although the next door downshift 4-3 valve is the same. One slight oddity I found was with the 1-2-3 sequence valve on the opposite side which has an O ring which just rolled out with the valve, but may be that is okay. I think I will now fit the other valve block and hope for the best! With regards, Matthew T.

I have managed some further dismantling and removing of valves and other components and I am providing another photo. Interestingly in the 3-4 transfer valve chamber there appears to be small triangular shaped hole at the corner which I initially thought was dirt that does not look right! I can fit the end of a pointy knife blade in the hole and I attach the best photo I can get. With regards, Matthew T.

On further inspection the hole at the base of the valve chamber seems to be a slot and there are a couple of others above so is meant to be there I think! Regards, Matthew T.

Just one other observation which is that in the attached diagram it appears to show there are wide and narrow springs on the two left hand valves, whereas on both my blocks they were on the first and third valves. The diagram also suggests two wide springs on the third, however, that is not present anywhere. I am not sure whether my observation is significant although the second valve is the 3-4 traction! Regards, Matthew T. PS. The second, third and fourth valves are not removable without further dismantling, due to the circlips shown in the diagram although all valves moved freely on both blocks.