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TR6 master cylinder conversion  Rating:  Rating
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 Posted: 03-17-2005 09:36 pm
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Mark Rosenbaum
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Originally posted July 2003.

============================================================

Recently the master cylinder (M/C) in my JH began exhibiting unmistakeable signs of incipient failure. Having heard that the success rate when rebuilding these is quite low, I decided that a new M/C was in order. It's fairly well known that the TR6 M/C is a drop-in replacement for the original JH part, and according to the pricing information I have the TR6 part is several hundred dollars cheaper.



Since Delta Motorsports doesn't offer TR6 M/Cs, as far as I know, I checked the archives of various British car bulletin boards to locate a reliable source. Concluding that The Roadster Factory had the best overall reputation, I ordered the part from them. Their catalog price was $200, with shipping another $10 or $15, but as it turned out they were having some sort of sale, so the part was $180 and shipping only $5. Unfortunately the part was out of stock and had to be ordered from England. This took a couple of weeks.



Since I'd been treating the studs securing the M/C to the brake servo with Liquid Wrench on a fairly regular basis for several years, removing the M/C was not a problem. Knowing that a great deal of brake fluid would surely be spilled in the engine bay, I lined the left side chassis rail with a thick wad of paper towels backed up by shop rags, and had a large metal coffee can immediately at hand to accept the old M/C once removed.

I used a flare wrench to loosen the ends of the two pipes connecting the M/C to the PDWA. Once these fittings were merely finger-tight, I removed the two 3/8"-24 tpi nuts that hold the M/C to the brake servo, then finished removing the brake pipes. The two brake pipes were then removed and followed the old M/C into the coffee can. (These pipes were removed solely to allow easier bench bleeding of the M/C, as described below.)

There was considerable surface rust on the forward surface of the brake servo where the M/C had sat, but this was removed fairly easily with a bit of wire brushing and the aid of an aerosol can of Berryman's brake cleaner. The M/C's bore, however, showed signs of somewhat heavier rusting, and I surmise that some of this rust was carried into the cylinder when I last bled the brakes, eventually causing the M/C's internal seals to leak.

This is a messy process -- REALLY messy if you spill any brake fluid -- but is highly desirable as it cuts down dramatically on the bleeding needed at the wheels. According to some sources, bench bleeding is also necessary to prevent damage to the M/C while bleeding the system after installation.

While one can go to considerable extremes to bench bleed a M/C, what I did was to connect the two M/C-to-PDWA pipes to the M/C, then connect a foot-long piece of hose to the free end of each pipe. I then propped up the M/C in one of the drawers of my tool box, and inserted the free ends of the two hoses into the M/C's fluid reservoirs. Then I filled the reservoirs with brake fluid and used finger pressure to gently depress the M/C's piston until only fluid was emitted from each of the hoses. The process took about five minutes. (Cleaning up the mess that occurred when one of the hoses came loose and piddled brake fluid all over my tool box took considerably longer.)

Though I normally prefer DOT4 brake fluid due to its much higher wet boiling temperature, the cap of the TR6 M/C says to use only DOT3, so, after a bit of pondering, that's what I ended up using. Hopefully this won't cause the new M/C to self-destruct.

Carrying the somewhat soggy M/C from the workbench to the car, I slipped it into place on the brake servo studs and installed the mounting nuts and washers not quite finger tight. The two rubber hoses used in bench bleeding the M/C were removed, one at a time, and the end of the associated fitting screwed into the PDWA. Once again, this is a messy process as fluid will be leaking from the M/C out the end of the pipe until the fitting is fully seated. The stud nuts were then torqued down (I couldn't find a spec for this, so picked 20 ft-lb), and the brake pipe fittings were tightened with a flare wrench. A quick press on the brake pedal resulted in a fairly firm pedal with the expected slightly spongy feeling one expects when there's air in the system. Bleeding the brakes took care of this.

I used copious amounts of aerosol brake cleaner to flush away all of the brake fluid that leaked out during the swap, and slid the rubber tube that fits over the clutch cable to a location where it would keep the cable from abrading the brake fluid reservoir.

In conclusion, this really is a simple swap without any hidden problems as long as the nuts securing the M/C to the brake booster aren't rusted in place.

Finally, thanks again to everyone who responded to my request for tips concerning the swap.

Mark Rosenbaum Kingman AZ 74 JH 16371

 

Dull Boring Technical Stuff

===========================

TR6 M/C.

The Roadster Factory's description for the M/C was 'T56 Master Cylinder Assy, Brake', with part number GI 64068822. The part, when received, came in a green Lucas box which also bore part-number-like markings of 'PMF 214' and 'GMC 234'. The casting number on the metal part of the new M/C was 64678258. A red plastic strip secured around the cylinder read '68822' which is obviously the last 5 digits of the Girling part number. This was followed by '6040' which, I am told, relates to the fluid percentages delivered to the front and rear brakes respectively. Next came the letter 'C' and finally the code '150P'. I don't know what either of these means.

Original JH M/C.

The factory item is Girling part number 64066027. The part on my car is either original from the factory or a long-ago replacement. It has a red-orange plastic strip bearing first the number '6027' then '08' then '60/40' then '97GS'. The plastic fluid reservoir bears casting number 77470129 while the metal body bears casting number 64676942 followed by '027' and a very large 'C' (which might perhaps actually be a G, as in Girling).

Brake Pipes.

There are two 3/16" diameter pipes that connect the M/C to the PDWA. Each pipe has a bubble flare and a male fitting on either end. These fittings have different sized threads as noted above, but in all cases their heads are 7/16" across flats. The shop manual claims these are 10mm across flats, but this was not the case on my car. For the aft port, the line was about 18" long and had a 7/16"-20 tpi male fitting on either end. For the fore port, the line was about 13" long and had a 3/8"-24 tpi male fitting on either end. The stock pipes fit the TR6 M/C without any problems whatsoever.

M/C Dimensions.

I measured various locations on the TR6 M/C as indicated below. In all cases, these dimensions match those of the original M/C.

Flange bolt mounting centers 3.22" to 3.25"

Flange bolt hole diameters 0.42"

Flangeside cyl. protusion OD 1.60"

Flangeside cyl. protrusion ID 1.00"

Fore Port (rear brake) threads 3/8"-24 tpi

Aft Port (front brake) threads 7/16"-20 tpi

I would think that any M/C that could be made to comply with the dimensions above should bolt up to the stock brake booster and work well enough. The two port threads are, IIRC, standard on the M/Cs used in most American cars, so there ought to be a horde of potential replacements if one is willing to fabricate a couple of brake lines. I will also note that European JHs don't use the PDWA at all but instead use a coupling for the rear brakes, and a tee for the front brakes.

Mark

 

 

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 Posted: 04-06-2005 10:10 pm
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Rory Clark
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Mark, did this TR-6 M/C conversion include the Servo unit.

How do you know the Servo is going bad? I have a Very slight showing of a leak on fluid and I wonder is I do not have a slight Vaculm leak. Overall the brakes have a "firm feel"

Rory 73-JH 13218 eng 3238
 

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 Posted: 04-06-2005 11:40 pm
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Mark Rosenbaum
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The TR6 conversion was the master cylinder only.

If brake fluid is leaking into the servo from the master cylinder, the master cylinder is defective and requires replacement as soon as practical.  A very large percentage of rebuilt British master cylinders seem to fail almost at once, perhaps due to counterfeit parts that some years ago were discovered in the distribution system, so I'd opt for a brand new master cylinder whenever possible.

A 'firm feel' to the brakes sounds normal.  With the car moving slowly in a non-traffic area such as a disused parking lot, you can test the servo by determining the amount of leg force needed to just lock the brakes with the vacuum line to the servo (a) connected and (b) disconnected and capped off at the intake manifold.  The latter case should require a very considerable increase in force -- perhaps 5 to 10 times as much.

If you think you have a vacuum leak, the servo can be tested while still on the car.  Simply apply a vacuum of about 20" Hg to its inlet and see how long it takes for the vacuum to drop.  A serviceable unit should maintain perhaps 15" Hg of vacuum for 10 minutes.  A really good one will hold the full vacuum for much longer than an hour.

I will note here that, unlike passenger cars with mild street camshafts, the JH with stock cams produces only about 15" Hg of manifold vacuum at idle.

In the event your servo won't hold vacuum, check the one-way inlet valve and its gasket before condemning the servo itself.

There's a truly excellent article on the Buckeye Triumphs website (don't have the URL, sorry, but a Google search should work) that is highly recommended to anyone interested in the topic.  The attached drawing has been borrowed from there.

Attachment: Brake servo internals.jpg (Downloaded 620 times)

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 Posted: 04-07-2005 02:56 am
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Rory Clark
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Thanks Perfect Info. I do in deed have 14-15hg at Idle.

Now I can move on. Yesterday I had Very little leak. Noticed tonight My back reserve (by firewall) dropped over 30%. (No so "little")

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 Posted: 04-13-2005 04:44 am
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Laurence Waarden
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I replaced my master cylinder with a TR 6 unit from Moss a few years ago.  Watch out for the resivoirs though, I have one that was poorly molded and leaked where it mates to the master cylinder. (I couldn't figure where the leak was for the life of me)  Regarding the servo: I had mine rebuilt and powder coated for a little over $125.00 from Partco http://www.partcoautomotive.com   I highly recommend them and they have done quite a few JH's.

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 Posted: 03-27-2006 11:52 am
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Jon Plowe
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Hi,

Great site, the info on many subjects has put my mind at rest - easy to get  paranoid regarding lotus engines and lucas electrics! Regarding brake master cylinders, after being quoted well over £100 for one I examined my old 1977 series 111 landrover and found that the girling cylinder was the same (same numbers but a slightly different shape reservoir) I bought a brand new one for less than half the price.  I have used one 1,000 miles, competed in sprints and hillclimbs with no problem. I'm all for supporting specialist suppliers, but 400% more expensive!

Jon

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 Posted: 03-27-2006 04:18 pm
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Dan Sommerfeld
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Jon,

We've discussed previously that there had to be other cars using similar master cylinders, and you were sharp enough to spot this.  A part number for the Land Rover master cylinder would be appreciated by many on this site.

Thanks,

Dan

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 Posted: 03-27-2006 05:36 pm
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Jon Plowe
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Unfortunately I don't have the LR part number but if you look on the web site for Paddock Land Rovers, Matlock, Derbyshire, uk and follow the links for spares > series LR > brakes > master cylinder - scroll down and you will be given a choice of two cylinders for twin line servo systems - it's one of those. The girling part numbers on one of the descriptions matched  the numbers on my JH cylinder. From memory there may have been a digit too many or a difference in the last letter/number, I guessed it related to the shape/angle/capacity of the reservoir. I bought the cheaper pattern part and have no problem with in 18mths and 2k miles. Should have written it all down!!

Jon

 

 

http://www.paddockspares.com

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 Posted: 03-27-2006 11:08 pm
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Ron Earp
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Got a new one from Victoria British for $100 even, just arrived two days ago.  Right here:

 

http://www.victoriabritish.com/features/t6/T6BR1.htm

Ron

Last edited on 03-27-2006 11:09 pm by Ron Earp

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 Posted: 03-28-2006 04:27 am
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Art DeKneef
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Great price Ron. I bought mine a month ago from them and it was $150.00 on sale. I wonder what has changed that the price has dropped some more. Maybe I should get another one for the other car at that price.

Art

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 Posted: 03-28-2006 04:15 pm
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Greg Fletcher
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Wow, that is an incredible price (hard to believe) and a fraction of what I've been getting them for. I assume these are still stamped as Lucas, yes? I've heard that the separate divisions of Lucas were bought up and reorganized by different companies, the old Lucas company as it existed for so many decades is no more. At this price it's simply impossible that they are being manufactured in the UK. I did see one recently that was was marked EU (European Union) on the box, so I suspect that production has most likely shifted to an Eastern European country. The manufacturers get the tax benefit of a EU product with a much lower labor cost and as a result, lower wholesale costs.

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 Posted: 03-28-2006 04:29 pm
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Ron Earp
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My says Lucas on it, but who knows in this day and age.  I will use it and let you know what happens.  I suspect that nothing will happen and it'll work as advertised.

Ron

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 Posted: 03-28-2006 04:38 pm
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Art DeKneef
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I should have mentioned earlier that Thailand was marked on the box the master cylinder came in.

But there is no Lucas shown anywhere on the box or master cylinder.

Art

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 Posted: 03-28-2006 04:56 pm
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Greg Fletcher
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That explains everything. Thailand!? I'm ok with anywhere in Europe, but English parts made in Asia really turns me off. I say that is total BS- is this what owners want? Cheap-ass parts for your "British" car made in Asia? I think it's an outrage.

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 Posted: 03-29-2006 11:23 pm
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Ron Earp
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I don't know where mine was made. But, I did install it and we bled the system, man is the pedal firm. A new master is a nice thing to have and I'll buy one for the race spares box too. Dang rebuild kits for the JH master are like $75 and mine was so out of round a rebuild scarcely did anything - should have checked the bore more carefully before rebuilding.

R

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 Posted: 05-17-2006 01:32 am
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D.Drake
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Ron
I am in the process of changing my M/C and purcahes a new unit from Obsolete Automotive
There is what looks to me to be a casting flaw in the flange that mates to the brake booster . I contacted Obsolete and they advised me that this was a modification to the unit and was there intentionally ,I doubted this very much until I followed your link to Victoria British . When I look at their product image it does look like the casting flaw is there as well !
Is there a similar notch on your unit and do you have any idea what the intended purpose could be ?
I have attached a jpeg  that hopefully illustrates what I mean

Attachment: photos from camera0002_2.JPG (Downloaded 88 times)

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 Posted: 05-17-2006 02:02 am
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George
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I have one of the Thai jobbies sitting on my kitchen counter for installation tomorrow and it does not have the notch out of it.  Doesn't seem like it would matter, though. 

BTW- One thing I just learned, when soaking the bolts on the booster with PB Blaster or whatever - I would reccommend soaking mating surface between the cylinder and the booster as well.  Even after I had the bolts off, the cyinder was really stuck on there.

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 Posted: 05-17-2006 12:11 pm
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Harkes
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hi, my TR6 MC, which i bought from Greg/JHPS has the very same 'flaw' as you call it. It seems to have a function, but i don't know what it is either. I think we can conclude it is not a flaw...

Does anyone know what its for?

erik, netherlands

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 Posted: 05-17-2006 09:45 pm
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Ron Earp
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I don't know what it is, but, it won't bother anything. It isn't a stressed piece where it is mounted and I honestly don't know if mine had it or not. I put it on, it works well.

As far as the comment about cheap parts being made in Asia, I'd suggest the word inexpensive instead of cheap.  Asia has some extremely good factories up and running in today's world economy that produce fantastic machine, electronic, and other goods.  People shop with their wallet and want a low price and quality, and by and large these days, they can get it.

All I know is buying one of these things for $100 beat the heck out of trying to rebuild the old one, which ended up failing and cost almost as much as a new master.

R

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 Posted: 05-17-2006 10:38 pm
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Greg Fletcher
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That is the world economy, isn't it? Everyone wants the $100 giant plasma screen TV. Personally, I don't think everything we buy and own needs to be manufactured in Asia, but that's just me. I go to a lot of trouble to find small, high quality shops in the US or the UK to get parts and services from. I'm sure there are folks that are completely unconcerned about that, but I find typically that the greater quality and attention to detail is worth the extra money. I'm in favor of English parts for English cars, although remanufacturing from the USA works for me also.

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