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healeyboz

healeyboz

Jedi Knight
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Dot 5 from dot 3. I know that the two are nowhere compatible so I thought that I would toss some ideas around with you all. I was thinking of draining the master and sucking as much fluid out of the lines with a pneumatic bleeder. The bleeding the system until the DOT 5 was the only thing coming through the clear bleeder tubes. What does everyone think? Does this seem like a possible transfer?
 
I have heard that you should flush the lines with alcohol before going from Dot3 to Dot5 or vice versa. I have also heard that when Dot3 or 4 mixes with Dot5, it makes globbity gloop. I don't have any personal experience though.
 
I drained the system, disconnected ALL of the lines and blew each one out with compressed air until it seemed clear before I reconnected them all and refilled. I also rebuilt all of the cylinders at the same time. I have heard from too many people that they congeal if the two mix.
Bill
 
Flush the whole system out with alcohol. Run a couple of bottles thru the system. I mean those drug store size bottles, not 5ths of Jack Daniels /bcforum/images/%%GRAEMLIN_URL%%/wink.gif
 
Never put Jack Daniels in your brakes. It is a real waste of good alcohol.

Restoring my wifes Beetle, I changed to DOT-5. I did replace all the cylinders and hoses, leaving nothing but the hard lines. I blew those out with compressed air then flushed with alcohol and followed with more air. I have not had to touch any of it since 1996 so it seems to have worked.

I have been told though that silicone is not always compatible with the rubber in our British brakes. Does anyone know for sure about that?
 
Think that was the orginal stuff.
 
True, DOT 3/4 and DOT 5 won't mix, and the results aren't pretty. When I switched over, I was replacing the master cylinder and all the brake lines at the same time. As for the wheel cylinders, I just took them apart and dried out all the old fluid, lubricating the seals with DOT 5 when I put them back together. If you do decide to use alcohol, be sure everything is dry before you refill it. Blowing it out with air is a good idea.

I would recommend taking the front cylinders apart to clean them, since the two piston design means it's darn near impossible to get the fluid out of the inboard side. For that matter, just blowing out the rears could still leave some fluid on the low side of the cylinder.

Shouldn't be any problems with rubber compatiblity.
 
Bayless said:
I have been told though that silicone is not always compatible with the rubber in our British brakes. Does anyone know for sure about that?
Click to expand...

I've been using DOT5 for about four years with absolutely not complaints but your results may vary! lol!


Boz, Just curious, why are you going through the trouble to change from DOT5 to 3?
 
When I went through my system 4 years ago, I converted to DOT5. My car sits a lot and has always had brake issues mostly due to moiisture causing rust in the cylinders. I replaced all cylinders and flexible lines. I blew out the hard lines with compressed air and flushed them with lacquer thinner and blew them out again until dry. I think the rubber in the new components is a different compound than the old. In general most all rubber made today is different than it was in the past -some better, some worse. I have not had any problems and my car still does not get driven very much. My MGB has not had the same problems with rust that my Sprite always had. I think the size of the cylinders is a factor and there are more aluminum components on the B. The only way I would convert to DOT5 is with all new cylinders and a complete flushing.
 
sqbsprite said:
I blew out the hard lines with compressed air and flushed them with lacquer thinner and blew them out again until dry.
Click to expand...

Wouldn't lacquer thinner destroy rubber? It dissolves plastic pretty effectively.
 
When I used the lacquer thinner there was no rubber to come into contact with. I made sure it was dry before re-assembly. I just wanted to make sure all the old stuff was cleaned out. Alcohol may work and is safer, but weaker at cleaning. Always be careful when using lacquer thinner for cleaning anything.
 
You may consider switching to Dot 5.1. It absorbs very little moisture, but mixes just fine with Dot 3.
 
Anywhere. It's typically marketed as "Synthetic" brake fluid. I have the Valvoline variety.

Just to be clear, when I say that it mixes with Dot 3, I mean that you don't have to be quite as vigilant when you flush the lines. You should be able to buy a big bottle of Dot 5.1 and just use that to flush the lines.
 
So I just went down to Napa to find the 5.1. It says that it is not silicone. Will it still eat paint?
 
This last winter I took my car completely apart and replaced my original master with a late dual master.
When I replaced the fluids I went with the synthetic and have had no problems. Good luck.
 
As far as I know, Dot 5.1 will eat paint. But maybe not as quickly as Dot 3. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
 
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