[dmorris1200]

[quote]I am going to be flushing the brake system on my Jag. The shop that will do the work suggested I use DOT 4 fluid. <hr></blockquote>
I don't understand what all the talking about flushing for silicone fluid is for. DOT4 fluid is NOT silicone. It is basically the same as DOT3 except for a higher boiling point. 4-Jaw and woodz already confirmed this. Most performance imports come with DOT4 from the factory so your Jag may already have DOT4 in it. If that info is not on the cap to the master cylinder it should be in your owners manual. Either way if your Jag currently has DOT3 or DOT4 in it you don't have to worry about any special flushing procedures. Here is an old thread from last year about the same thing.

<a href="http://www.hotrodders.com/cgibin/ubb/ultimatebb.cgi?ubb=get_topic&f=18&t=000223" target="_blank">Dot 5 Silicone Brake Fluid?? Yes or No ??</a>

I would do what the shop told you and use DOT4. You can add it to the master cylinder as you bleed the old fluid out of the bleaders. Do not use DOT5.

[woodz428]

Not all DOT 5 is silicone, some are synthetic and don't have the air absorbtion problems associated with silicone. I think he's going with the synthetic DOT 5 which has a higher boiling point yet. If he were going with the silicone I would agree but I've used the synthetics in my GSXR with great results (as well as the silicone when it came out that had to be bled every other week to eliminate the absorbed air). The DOT 3&4 fluids absorb moisture out of the air which is what causes the corrosion common when calipers are opened for rebuilds and the synthetic doesn't do that either, so I think it is a better long term fluid.

[dmorris1200]

Once again DOT5 is SILICONE fliud period!!
Synthetic brake fluid is designated DOT5.1

If you read either the link posted by Joe Daddy in his earlier thread or the link I gave to the prior thread on this issue you would see that 4-Jaw specifically stated that the synthetic fluid is designated DOT5.1 not DOT5, the same thing is stated in Joe's link. Also stated in the link from synlube.com is that DOT5.1 is based on Polyglycol chemistry and is fully compatible with conventional brake fluids requiring DOT3 or4 fluids (no special bleeding procedures required because they mix). So once again DOT5, silicone = no good. DOT5.1, synthetic = acceptable upgrade. Either way I would still go with DOT4 like his shop suggested in the first place since it's been working fine for years, although the 5.1 does look pretty good-just no first hand experience with it. And having rebuilt many brake calipers over the years in my opinion most of the rust is usually on the outside of the caliper but once the piston is removed the caliper bore usually only needs a little cleaning with brakeclean and most pistons clean up with a shop towel (except extreme cases). And since the caliper seal stays fixed in the caliper bore and seals against the piston surface the piston surface is the most critical part to the correct sealing of the caliper. I have rarely had to replace a piston as part of a caliper overhaul. So once again to stop confusing people...
DOT5 = silicone fluid not compatible with DOT3,4,or5.1
DOT5.1 = synthetic fluid compatible with DOT3&4




[ April 04, 2003: Message edited by: dmorris1200 ]</p>

[Jag Daddy]

The reason I want to flush the system is as I pulled the old reservoir out it had black sediment in the bottom. Since it's in there I would assume it's in the whole system. If I'm putting a new master cylinder a new brake reservoir and a new rear brake line I just thought it would be best to purge the system befroe refilling so I don't pull that junk back up to the new master cylinder. Any thoughts


Regards
Mark

[dmorris1200]

It's never a bad idea to flush your system. We do it as a service at work. But what you don't want to do is get yourself into some crazy flushing procedure for nothing. Use what's compatible in your system and just keep pushing the new fluid through the system. Give yourself a brake and don't make this into something bigger than it needs to be. Just my advise.

[4 Jaw Chuck]

What he said!

[woodz428]

Yes.. it is actually 5.1, but it meets the or exceeds the DOT 5 standard so I was being a little loose , that's why I was enphasizing the SYNTHETIC, so he would avoid the silicone (hell, I've still got a case of that stuff from when it was supposed to be the next greatest thing)

[dmorris1200]

[quote]Originally posted by woodz428:
<strong>Yes.. it is actually 5.1, but it meets the or exceeds the DOT 5 standard so I was being a little loose , that's why I was enphasizing the SYNTHETIC, so he would avoid the silicone (hell, I've still got a case of that stuff from when it was supposed to be the next greatest thing)</strong><hr></blockquote>

Didn't mean to bust balls but I could just see a bunch of guys out fighting over whether or not DOT5 is silicone or not because of what they read here. They designated the synthetic as DOT5.1 to prevent such confusion. I think you said that you have used the synthetic DOT5.1, what do you think of it? I have always used DOT3 or4 with the exception of my Harley which takes DOT5.

[woodz428]

I used in in my GSXR 750 that was built (suspension, ported, big bore kit with 14:1, cams and braided brake lines). I liked the way it worked and went to it for the same reason I initially tried the silicone stuff, as winter sets in it wasn't ridden as much and I didn't like the idea of the corrosion build up over the 3 or so months of cold moist weather. It didn't seem to have the drastic effects on the plastic and such either, and I liked the feel. Not that I ever had any problems with braking or feel with the 3 or 4, but when you're working on other peoples high zoot machines, I always like to have first hand knowledge as they always want the "new" best thing.

[ April 05, 2003: Message edited by: woodz428 ]</p>

[dmorris1200]

[quote]Originally posted by woodz428:
<strong>I always like to have first hand knowledge as they always want the "new" best thing.

</strong><hr></blockquote>

Amen to that! I rarely ever will recommend something because of what I read about it. I like to know for myself. I often wish my Harley used DOT4 like most of the other bikes out there. It it did I would probably try the DOT5.1 in it. As it is I just flush her out every so often, never had any problems yet.

[adtkart]

I sure am glad that there are plenty of people out there to try this new stuff. I hate having to try it myself, and don't recommend anything I haven't tried. I do, however, pass along the bad things that I hear about the stuff that I haven't tried. That way someone else can decide if they want to try it. That covers me if they decide to try it, and they usually come back and let me know if they decided to try it on their own, and the results.

[farna]

uh...well... sorry about the mix-up I had with DOT 4 and 5, FIVE being mostly silicone based. At least you have the low-down on silicone now! I think you got enough on DOT 4 too.

[ChevelleSS_LS6]

how often should the brake lines be flushed, anyway (miles, years, etc.) <img src="confused.gif" border="0">

[Jag Daddy]

Well from what my research telles me about every 2 years with standard DOT 3 and 4 fluids, some synthetics seem to be able to go longer. Synthetic fluid looks very interesting to me. The cost may be a bit more than your willing to spend.

Regards
Mark