Brake Fluid

[Ryunker]

What is the correct brake fluid for a '67 Avanti II? Dot 3? Dot 4? Does it really matter? I am geting ready to do rear brakes on this car, and will end up rebuilding wheel cylinders and want opinions as to what type to use and problems associated with either of them. Currently the brakes on the car work OK, but when you stop in reverse the left rear wheel locks up and will no longer roll. Without taking it apart I think the brake self adjuster springs are broken and the brakes are out of adjustment. A short time will tell, I have just ordered the "Brake drum puller" from JCWhitney. I found from another post they are tapered?

Rich Yunker

[Gunslinger]

Use either DOT3 or 4 brake fluid. Avoid DOT5 silicone fluid unless you completely...and I mean COMPLETELY, flush out the entire brake system. DOT5 does not mix with DOT3 or 4 and creates many problems. In fact, it would be better to replace the brake lines, hoses, calipers and wheel cylinders if you want to use DOT5...anything that is touched by fluid. DOT5 does have some real advantages...it doesn't harm paint if it's spilled, it's not water based and won't absorb moisture so corrosion is less an issue, but as I said, it doesn't mix with DOT3 or 4, it takes more effort to completely bleed air out of the system, and is more expensive. Most, if not all, performance car makers specifically warn against the use of DOT5 in their cars as hard maneuvering creates air bubbles in the system and allows a mushy brake pedal. That's why it's so important to fully bleed the system of air.

Most likely, your '67 probably came with DOT3, or whatever it was called then (I don't believe the "DOT" designation was in use then). I know in 1970 Avanti Motors was saying in their brochures that they installed silicone fluid at the factory, but I have seen no documentation to exactly when they started with it...just with 1970 sales materials. It could have been done prior to that. The best thing you can do is completely flush your brakes and replace the rubber hoses just on general principles.

Brake parts for the car aren't at all difficult to come by...but "not at all difficult to come by" doesn't necessarily translate to inexpensive! It depends on the parts needed. You will find the vendors who specialize in Avanti's and Studes are the best places where you'll find the correct parts. I found out the hard way that parts someone's else's application guide say will work don't. Try and stick with our vendors and you'll be happier and get the correct parts sooner. Any parts such as brake shoes, master cylinders, calipers, etc., which you choose to replace that can be rebuilt, send them in as a core trade. We all need to keep rebuildable parts "in the food chain" or parts will get even more expensive down the road.

There's nothing wrong with rebuilding your rear wheel cylinders as long as the cylinder and piston are not rusted and scored. A light honing is normal. Before you start trying to rebuild them, inspect them internally to see if they are, in fact, rebuildable. Spray penetrating oil on the bleeder valves and let it sit for a day before trying to turn them. If they snap off, you haven't wasted time and money with rebuild kits and end up with it being unusable anyway. Also spray down the eccentrics that adjust the rear brakes...if they don't free up you'll need replacements as well.

Some Avanti II's came with the tapered rear axle (especially early on in production) and some came with the flanged axle. What probably happened is as cars were assembled they installed whatever rear end/axle set was next in line in the parts bins. My '70 has flanged axles but I've heard a few owners with cars later than mine say they had tapered axles on their cars.

If you haven't already done so, get copies of the Avanti parts and service manuals. They are worth it far beyond their initial cost for the grief they save you in the long run.

[geojerry]

Bruce is totally correct on avoiding the use of DOT 5 in our Avanti's. When my 78 II master cylinder died and leaked fluid, my master mechanic installed a new GM Master Cylinder and filled with DOT 3. He said under no circumstances use DOT 5 in these cars. DOT 5 "eats" rubber, gaskets and causes bubbles, as stated by Bruce.

[Charlie Kile]

Bruce is totally correct on avoiding the use of DOT 5 in our Avanti's. When my 78 II master cylinder died and leaked fluid, my master mechanic installed a new GM Master Cylinder and filled with DOT 3. He said under no circumstances use DOT 5 in these cars. DOT 5 "eats" rubber, gaskets and causes bubbles, as stated by Bruce.

The orihinal master cylinder in my 84 had a label with red letters that said "DOT 5 Fluid only".

Charlie RQB3921