TR2/3/3A Using DOT 5 Brake Fluid On TR3A

[mallard]

Randall that's a interesting artical from Moss. I wonder if my mistake in rebuilding the clutck and brake system is that I used Lucas PFG102 Rubber Grease? It states that it can be used when in contact with brake fluid. I used the same stuff on my current TR3 rebuild. When they wrote the specs for the grease it may have only been ment to be used with DOT3 fluid. Could this be my problem?

 

[TR3driver]

When they wrote the specs for the grease it may have only been ment to be used with DOT3 fluid. Could this be my problem?

Seems unlikely to me, but what do I know? (I use DOT 5 to lubricate the bores & seals, not the grease.)

 

[mgedit]

Very interested in this discussion. I had my slave rebuilt by Apple Hydraulics, but it is not yet installed. Here is the slip that they included with the installation instructions. Does not say "will", but says "may not". I had planned to use 5.1 but now I'm still unsure. Cheers, Mike

 

[3798j]

Apple Hydraulics sent a similar warning back when they rebuilt my TR4A's brake calipers in 2002. After installing, then filling and bleeding with DOT 5, they were fine and continue to be.

 

[mallard]

I think that the fact that there is any doubt at all about silicone and the seals any manufacturer, or rebuilder is going to side on the safe side and warn against it's use.

What type of seal, or rubber component is used in cars that require DOT5 fluid? What do the racers use?

 

[sail]

Seems unlikely to me, but what do I know? (I use DOT 5 to lubricate the bores & seals, not the grease.)

Seems like new cylinders often come with grease, would you just wipe them clean and smear with fluid?

 

[TR3driver]

Seems like new cylinders often come with grease, would you just wipe them clean and smear with fluid?

If they came with anything sticky (like grease), I'd wash it off with brake cleaner first. Then dry and coat with clean DOT 5 just before assembly.

But I've never seen a new cylinder come coated with anything.

 

[TR3driver]

What do the racers use?

DOT 5 is not a good choice for racing. The serious racers use special "racing" fluids that have very high dry boiling points, and then change them every season (so they never become "wet").

Here's some more information that some may have not seen:

 

[sail]

I just got a new clutch master cylinder from TRF that came with poop brown grease under the dust cap and on the push rod area. The brake master had nothing.

 

[martx-5]

When they wrote the specs for the grease it may have only been ment to be used with DOT3 fluid. Could this be my problem?

Seems unlikely to me, but what do I know? (I use DOT 5 to lubricate the bores & seals, not the grease.)

I always remember that the "grease that was supplied was to be used to fill up the outer boot where the push rod goes through after the cylinder was assembled.

 

[GBRandy]

This is a decent article I have used in the past to better understand the differences in brake fluid characteristics and identifications:

https://www.afcoracing.com/tech_pages/fluid.shtml

It seemed appropriate as a refresher here.

 

[HerronScott]

I always remember that the "grease that was supplied was to be used to fill up the outer boot where the push rod goes through after the cylinder was assembled.

Art,

That's what I recall as well. You just used brake fluid to lubricate the seals themselves as Randall indicated.

Scott

 

[HerronScott]

Very interested in this discussion. I had my slave rebuilt by Apple Hydraulics, but it is not yet installed. Here is the slip that they included with the installation instructions. Does not say "will", but says "may not". I had planned to use 5.1 but now I'm still unsure. Cheers, Mike

Did you really mean DOT 5.1 or just DOT 5?

DOT 5.1 is *not* silicone, is hydroscopic and will eat paint but it does have higher wet and dry boiling points.

Scott

 

[mgedit]

Scott ... yes, I was interested in using DOT 5. Thanks for pointing out. Cheers, Mike

 

[CJD]

I've used the supplied grease in the past for mechanical parts, like pins, shoes or clevises...but never for the seals or any hydraulic parts. Everything I've ever read or learned says to use nothing but fresh brake fluid on the internals...

I was sitting here thinking, but can't remember ever buying a new master cylinder, so can't comment on whether they come with grease in them or not. I think I always rebuilt them, and without grease. I have purchased new slaves for drum brakes...but don't remember seeing any noticeable grease there either.

John