Switching from DOT 5 silicone to DOT 4

[mkeith]

My Milano's brake master cylinder recently failed, & in my search of the car's service records to see if it had recently been replaced, I found that the brake & clutch hydraulics had been converted to DOT 5 silicone fluid. It was done in '93, & no brake hydraulic components were replaced at that time.

What possible problems could be encountered in switching from silicone to DOT 4? I would prefer to go to DOT 4 because I don't like silicone fluid's high air content, & I have 2 unopened liters of ATE blue on hand.

[alfajim]

There should be no problems in switching back to a good dot 4, just do a complete flush. Silicone Brake fluids have caused me many headaches over the years and I usually avoid them. Most abs systems don't like it also the rear calipers in alfetta, GTV-6, and milano.

[nizam]

Something to remember about our Milanos... they're reaching 15 years of age. The rubber dust boots, o-rings and seals are on the end of their useful lives.

In principle, there should be little day-to-day difference going from DOT5 to DOT4. However, the very action of flushing your system could aggravate a seal nearing the end of its life. This could lead to a coincidental 'finding' that going from DOT5 to DOT4 causes leaks at the caliper, master cylinder, etc.

On my 75/Milano, I used to be religious about 'the best' DOT4 fluids, but what I found to be even more paramount to continued braking prowess is the frequent flushing of the fluid itself; especially if you track the car. My first few years of track events saw me lose brakes at the end of a session, caused by boiling fluids or overheating pads. Over time, with more (driver) practice and constant bleeding/flushing of the system I have not had any brake issues on the street nor on the track.

Now my car gets a steady diet of off-the-shelf Castrol LMA (DOT4) fluid. Easy to find, and works just as well as my previous expensive 'top of the line' brake fluids! I've also changed most of the seals (<5 years old).

[mkeith]

This car will be my daily driver once I sell my truck. Therefore, if a seal is on the verge of failing, I'd rather have it fail, & deal with it before my truck's gone. The M/C will be new; so it will only be the calipers I'll have to worry about. The clutch hydraulics are relatively fresh. I don't think the hydraulic system in this car has been flushed since it was converted to silicone in '93. The reservoir was horribly dirty. It took forever to get it clean.

In a former life (before house & baby), I used to run a VW Golf in SCCA ITB; so I'm already in the habit of anually flushing brake fluid. I use one of those power bleeders from Motive Products. That thing is the best. I like using ATE fluid even though it's a little expensive. Alternating between their regular fluid & their blue makes flushing very easy.

Later,

[JoeCab]

I have also found that Castrol GT-LMA works almost as well as the high priced brands when it's fresh.

[DOM!]

I also have been using Castrol GT-LMA in the Alfa's, VW's, and Ninja. I like it a lot and pedal feel is real nice.

I want to try the Ate Blue fluid but when I used to be Crew Cheif for my friend's GT4 Rabbit, getting the system flushed right with that fluid was tough!

I'll stick to LMA..

[mkeith]

What made it so tough? I've never heard of that being a problem. I used to run a Golf in ITB, & I used ATE in it. I also used some Motul that Porterfield sent me with a set of their brake pads. Never had a problem bleeding or flushing the brakes with either one. Of course, it IT, we have to use the stock braking system. Your friend's GT car may have had a completely different braking system. GT-LMA is good stuff too. I often use it in place of the regular ATE, but I still like to use ATE blue for every other brake system flush because the color difference makes it so easy to tell when you're done.

Anyway, I flushed the brake system in the Milano with ATE blue when I installed the new master cylinder. The only problem I had is that the brake bias valve failed. It started leaking after the first drive in the car with the new m/c, & it leaks a lot. I don't think the switch from silicone to DOT 4 had anything to do with it. I think it was probably on the verge of failure, & the pressure bleeder I used to flush the system pushed it over the edge.

No big deal; I was told by a friend of mine who races a GTV6 that retrofitting the proportioning valve used on the early GTV6's in place of the bias valve will enhance braking performance because it allows more brake torque to go to the rear brakes. The bias valve used on the Milanos & the late GTV6's was adopted because of customer complaints of rapid rear brake wear. Better yet, the same friend let me have the proportioning valve off his '81 GTV6 parts car. I'll gladly trade some additional rear brake wear for better overall braking, especially when I get the part for free.

[JoeCab]

Quote:

I'll gladly trade some additional rear brake wear for better overall braking

[mkeith]

Interesting thought. Do early GTV6's tend to overheat their rear brakes more quickly than Milanos & late GTV6's? I thought rear brake overheating was an equal concern among all transaxle cars.

Either way, I don't think it will be much of a concern on mine as it is a street car. I'll probably do an occasional track event though. It was a long standing concern on my friend's race car; especially for enduros. A side exit exhaust & cooling ducts to the rear brakes have taken care of it.

I'm going to put some header wrap on the portion of the rear exhaust that is near the brake caliper as a precautionary measure. I've also bought some Porterfield street compound pads from Andy Kress which I'll put on the car as soon as the pads currently on the car wear out.

[DOM!]

The actual bleeding was not the difficult part. The part that was tough was getting the pedal feel right.

I never liked how it felt, grabbed low and I thought they were too spongey no matter what..

[JoeCab]

Whenever I'm satified that I have a good bleed but still have poor pedal feel I use this trick. I have no idea why, but it works.

Use a 2x4 or broom handle to hold the brake pedal fully depressed for at least 24 hours. After that, the pedal is much firmer.

[Sniady]

Where do you guys purchase youre Porterfield brake pads from? Whats the price?

[mkeith]

I bought mine from Performatek. Here's their price list for Porterfields. http://www.performatek.com/frOnlineCatalog.htm

Any place that sells Porterfield pads can supply them for an Alfa, but Andy is a great guy to deal with. I also bought his polyurethane bushing for the nose of my de dion tube.

[AlfaRacer75]

Quote:

Originally posted by Sniady Where do you guys purchase youre Porterfield brake pads from? Whats the price?

[Sniady]

Chip,

Thanks for the number.