Sunday, June 13, 2010

AL4 Hydraulic Valve Block

After finding the AL4 transmission rebuild manual a few days ago, I had the confidence to dismantle the AL4 hydraulic valve block. The gear change has not been smooth and I've suspected sticky valves all along. The transmission oil is almost 7 years old and clocked 77,000km. Since I planned to do a transmission oil change anyway, I decided to clean the valve block before putting in new oil. Also cleaned was the oil pressure sensor, located just beneath the block.

WARNING! Don't try doing this on your own if you don't know what you are supposed to do and not familiar with hydraulic valves. Doing this wrong can permanently kill the transmission.

There are two square-shaped strong magnets at the bottom of the lid, to collect any metal bits.

Rust where there isn't supposed to be any. This is a sure sign of water getting into the transmission. In this tropical rainy weather, it is a good idea to change the oil frequently to get rid of any water.

This block is still using the old/obsolete type of solenoid valves part 2574.10. These should be replaced with the newer Borg Warner valves part 2574.16, which will require an ECU software update. But unfortunately there's no Peugeot service centre in town that can do this, so I'm stuck with the old valves for the time being. Anyway the valves are still working, so I'm not too bothered to change them yet.

These are the sequence electrovalves, EVS. I've switched EVS5 (reverse gear) with EVS2 (for 2nd gear and 4th gear) because shifting from 1st into 2nd gear is intermittently not smooth and I suspect EVS2 not working properly.

The webbing can be wiped clean using lint-free cloth. I used cleanroom wipes since I have lots of it. I also took out all the EVS and sequence valves to clean them and drain out the old oil. The main block and auxiliary block was separated to allow all the old oil to come out and allow cleaning of the webbing and plates.

The result of the cleaning and new oil is a smoother gear change.

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