CMP fluids question ..........

[cantankrs]

I'm interested in where this silicone info is going - perhaps it should have its own thread in the restoration forum? A couple of years ago I enquired with a local, very experienced brake man, about whether I should bite the bullet and switch a light crane I have over to silicone brake fluid while I was overhauling the brake system and he flat out said don't touch the stuff. He wouldn't elaborate and seemed to have no love for it. I don't think he was trying to con me in any way. I just don't know whether he was warning me off due to cost, or some other reasons. Prior to that everything I'd heard said it was the go for restored vehicles.

Regards

Alex

[Phil Waterman]

Alex- your point is well taken, this topic does deserve detail treatment and it has been discussed in the past below are some of the threads. Unfortunately the MLU search feature works fine and other times it gets finicky. Today for example I typed in silicone brake fluid and got a number of responses, and then I typed in just silicone and got more. Yesterday I tried the same searches and got nothing. So if you get no hits on a search try again later.

Now back to silicone brake fluid here are some of the threads:
http://www.mapleleafup.org/forums/sh...ne+brake+fluid
http://www.mapleleafup.org/forums/sh...ne+brake+fluid
http://www.mapleleafup.org/forums/sh...ne+brake+fluid
http://www.mapleleafup.org/forums/sh...ne+brake+fluid

Several good points have been made in the past:

The first silicone brake fluids that came out had real problems and many providers/manufactures of master cylinders, brake cylinders, sleeving would not warranty there products if silicone was used.

If you are completely redoing a brake system (replacing or rebuilding all the parts) going over to modern silicone brake fluid should not be a problem and probably will give the advantages of silicone. But DO NOT use any NOS rubber parts, lines, cups or boots there maybe a compatibility problem. Be sure to use all new stock rubber parts from a known major brand. (This is probably a good idea know matter what fluid you use.)

The last point that has been made in the past discussions is that to change over, you really need to be sure that you get all of the old fluid and more importantly the dirt out of the system.

Personally - I think that one of the major maintenance problems with CMP brakes is us the users. We have all been spoiled by self adjusting brakes. Because the shoes/pads automatically adjust on our modern trucks and cars they have bigger brake fluid reservoirs because they are checked so infrequently. CMPs with there manual adjusting brakes need to be adjusted by the book. When properly adjusted the master cylinder is only moving a small amount to apply the brakes, which means there is very little air being drawn in and out through the vent on the filler cap thus less moisture is drawn into the system. When properly adjusted the brake shoes on a CMP do not have to move very much to fully apply. (This assumes that the drums are not oval shaped and shoes are not worn out)

Over the years I have been impressed with the braking power on HUP and on the C60, the HUP had has no booster while my C60S and C60L both have brake boosters. Compared to some of the US military trucks I've driven CMPs have bloody great brakes. (This however could be a maintenance issue) But when you look at the brakes on a 3/4 Dodge and compare it to a HUP you sort of wonder what was Dodge thinking.

One finial point – Alex I’m willing to bet that your friendly brake experts feelings about silicon brake fluid was centered around the rubber parts compatibility issue and the differences in tolerances between modern systems designed for silicon and those systems designed for regular DOT 3. Which is a very good point to consider.

[Neil Ashley]

I have been in the REME TA for 17 years and one of the most common jobs I do when working in workshops is replacing the Master Cylinders on trailers which have seized up due to lack of use. This is despite changing the brake fluid on a regular basis.

Silicone Brakle Fluid in an application like this could save thousands of pounds a year.

[Bob Carriere]

Just to echo Phil's point........

Last weekend, just a spur of the moment thing...... we decided to see if I still had brake pressure on my C15a which slept in a canvas tent all Winter.

Now my experience with M 37, M43 and PW was that the pedal would drop to the floor and a total bleed job would be needed...... that happens every year on my Dodges...... low and behold.... after two pumps, by hand, we had full pressure.
Sat on the beast and puched hard to see if it would bleed down.... held real thight......

So we pushed our luck a little further and tested to see if the battery still had life..... shit the engine started no problems at all......

Now when I rebuilt my C15a I installed new wheel cylinders, new steel and rubber lines and a rebuilt SS sleeved master, done by John Stuart of Stoney Creek, Ont. I hesitated like most to convert to silicone..... read all the pros and cons of the new fluid...got totally confused with the controversy...... some early experience were very negative..... it is important to note that most high end Ford cars (Lincoln and Jags)and trucks have switched to the modern silicone fluid......

For good dependable brakes do not hesitate to get new linings and get the drums turned clean..... and while at it..get them to "arc" grind your new linings to sit properly in the arc of the drums.....

If I had a chance to redo the full system of a Dodge, I would switch to synthetic silicone fluids. There are limits as to the improvement of the sick design of the flexible flower pot brake drums of the M37 as the stretch oval when braking hard..... it is a design limitation.

I would not consider using old, seemingly good, brake lines and would not try to flush them clean but rebuild the whole brake setup...... expensive.. Yes..... but so stopping a CMP on the rear end of a Honda.

Phil's expereince with the CMP is based on driving his trucks in the hills of Vermont and New Hamshire at a comfortable 50 mph... so when he says he can stop... he is not talking parade speed....!!!!

BooBee

[cletrac (RIP)]

Going back to Terry's original question, I'd just use 80-90 multiviscocity gear oil in all the gear cases. There aren't any benefits to the heavier stuff unless your seals leak too much.
As for brake fluid' I'll stick with the old regular stuff. I've driven millions of miles on it with no problems so I can't see any reason to change now.
For engine oil it's hard to beat straight 30 weight in the summer and something like 5-30 for cold weather. Synthetics in these old powerplants would likely overstress the seals and British Columbia authorities don't like dripping motors, do they?

[cantankrs]

Originally Posted by Phil Waterman

Alex I’m willing to bet that your friendly brake experts feelings about silicon brake fluid was centered around the rubber parts compatibility issue and the differences in tolerances between modern systems designed for silicon and those systems designed for regular DOT 3. Which is a very good point to consider.

Originally Posted by Bob Carriere

I would not consider using old, seemingly good, brake lines and would not try to flush them clean but rebuild the whole brake setup...... expensive.. Yes..... but so stopping a CMP on the rear end of a Honda.

Hi Phil and Bob, and Neil,

So the brake man was probably thinking just that, that at the end of the day Safety and not using other objects (or people) to stop against is paramount.
Thanks for all your info - much appreciated.

Regards

Alex

[Barry Churcher]

I would agree with Cletrac. I have never had good luck with silicone fluid and DOT 3 when used properly will give better brakes. 80/90 gear oil preferably GL-1 as opposed to the more readily available GL-5 will work for the trans, transfer and diffs. GL-1 is not hard on yellow metal as is the GL-5. You don't need the EP additives of gear oil in the trans so you could use a good quality 50 weight detergent oil. HD 50 is the same viscosity as 90 gear oil. The best engine oil is one of the high mileage oils (Valvoline is one). Newer motor oils have less zinc and the zinc is important for flat tappet engines. Like lead in the gas it is a lubricant and a cushion. It also works as an anti oxidant to reduce corrosion. The newer engines have roller rockers and no zinc. Zinc is hard on catalytic converters and will contaminate 02 sensors. The high mileage oils have more zinc or you can now buy good zinc additives. Motor oil has changed significantly in the last 10 years and it is going to get worse for old engines. A very good additive is GM's EOS. It has been around forever and works well.
Barry