The Triumph Dolomite Club - Discussion Forum

The Number One Club for owners of Triumph's range of small saloons from the 1960s and 1970s.
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PostPosted: Sun Nov 24, 2019 7:49 pm 
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Joined: Thu Sep 28, 2006 9:06 pm
Posts: 926
Location: Bristol
For some reason the clutch system on the 1500cc engine seems to give more problems than any of the other dolomite clutch hydraulic systems.

On Friday 2nd November “standardthread” made the following statement on this discussion board in his topic named “Tandem brake master cylinders” - No elephant in the room. Old car, cast iron clutch slave, hydroscopic brake fluid, or was, rust in the slave causing pressure loss and failure. When it happened the intention was to replace the seals on the slave and master, slave yes, the ones I ordered were the correct size, the master should have been correct, no, it had been replaced by a ¾” version so the seals didn’t get changed.

This certainly makes me wonder if the later 1500cc dolomites were actually fitted with ¾ inch bore diameter master cylinders at build as the Official Triumph Dolomite range 1976 onwards parts catalogue indicates that the 1500cc cars are fitted with a part number 158695 which is different from the other OHV engine cars which use a part 138928 (This item has been superseded by a part GMC1023). I have been unable to find any details of Part number 158695. Rimmer Brothers documentation also indicates that part 158695 should be used at a cost of £122.40p. Rimmers were unable to tell me what the difference is between the part 158695 and the GMC 1023. Most other suppliers quote the GMC1023 as being the Master cylinder for 1500c engine but there are a number that do not quote a part number for the 1500cc engine. I accept that a GMC1023 will work if the system is bled completely of air and there is very little or no wear in the pivots that make up the clutch system.

When I actually checked the bore size of a number of old ex 1500cc clutch master cylinders I found that the majority were 5/8th inch bore but there was also a 0.7 inch and a couple of ¾ inch in the batch that I have collected.

If you look at https://www.demon-tweeks.com/uk/girling ... ir-249578/ you will see that they can supply master cylinders with either 5/8, 0.7 or ¾ inch bores at a cost of £72.91 which look to be the same design as used on the 1500 dolomite. There would be a need to change the push rod, so that the original is retained. I have not been able to identify a current part number for either the 0.7 or ¾ inch bore master cylinders or the relevant seal kits. Can anyone provide this information ?

My assessment is that by fitting a master cylinder with a larger diameter bore the hydraulic system would move the slave cylinder piston slightly further for the same movement distance of the clutch master cylinder. This as a result, I believe, would mean that the system would be able to cope with a small amount of air being accidently left in the hydraulic system and it would also be able to take up any wear that had taken place in the various linkages.


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