DOT3 or DOT4 - How full is full? Manual is vague

First of all I plan on looking at my brakes/calipers/etc better tomorrow and try to check for delamination and stuff.

My 82 XJ750J Maxim manual said to use Dot3 fluid. However the reservoir on the right handle says to only use Dot4.
Non-Original reservoir?
Use Dot3 or Dot4 (I bought but not opened Dot3 recently based on manual)

The "clear" level check window on the brake fluid reservoir is all cloudy. So I tried to open the top. Left screw was rust colored and difficult to loosen. The right screw started to strip (Philips) on the very first attempt, so I stopped for now. (Time to find the dremel I think). Might also get a quote from our XJ Parts guru

As I said I intend to check out the brakes properly tomorrow. However my "brake" warning is on constantly on my "dash panel", as is the battery and one other thing. So I'm guessing the brake fluid is low or worse. Sound plausible?


EDIT: Forgot to mention front break squeeezing is NOT lighting up the brake light... /confused

EDIT 2: Got the cover off with a slightly larger/better screw driver and a few taps with a hammer to drive it into the screw head a little.

How full is full enough? My manual just says add enough fluid if low.
My fluid is just below the very top of the window,buy below the molded in fill??? line?

 

Re: DOT3 or DOT4 - Conflicting Info

Sounds like someone swapped the MC lid. Probably destroyed the old one in a fall down or cutting off stuck Philips screws.

Originally they used DOT 3. DOT 4 has a slightly higher boiling point. Personally I'd use the DOT 3 if I already had it on hand. The DOT 3 and DOT 4 fluids are compatible so there is no concern you might be mixing them.

 

Re: DOT3 or DOT4 - Conflicting Info

use it since you have it. but it's being phased out in place of dot4. i haven't shopped for brake fluid lately but i think 3 is already getting rarer to find.

 

Re: DOT3 or DOT4 - Conflicting Info

using dot3 in place of dot4 is the wrong idea to look at, brake fluid isn't backwards compatible, however you can use dot 4 in place of anything that requires dot 3. and being since dot 3 is getting phazed out your best bet is either stocking up on dot 3 or just forget about buying it and start using dot 4. and since your master reads dot 4 i'd buy dot 4

 

Re: DOT3 or DOT4 - Conflicting Info

Dot3 was readily available at my local Walmart. The only Dot4 I saw was a synthetic...

Since I'll probably be dremel slotting the screw head and/or easy out'ing the screw who know's what condition the cover will be in let alone the overall brake system...

I hear Charc is great on prices and speed... I have a feeling I may be ordering from him like 10x this summer...

 

Re: DOT3 or DOT4 - Conflicting Info

No compatibility issues with adding DOT3 to DOT4, you just lower your boiling point. I'd step up to the DOT4 when you run out of the DOT3.
I predict a new M/C cover screw in your future...

 

Re: DOT3 or DOT4 - Conflicting Info

There is a DOT 5.1 rating available at stores here, which states that it is backwards compatible with DOT 3 and 4, non-corrosive on metal surfaces and rubber, and comprised of ethanol ethers (thus organic).
I can't seem to find any DOT 4 nearby. Have any of you guys tried this formula?

 

Re: DOT3 or DOT4 - Conflicting Info

I've picked up a dremel style tool, a screw extractor bit and new screws

4x12 - Not black but it will do for now
Sucks that its raining again

EDIT:
Got the cover off with a slightly larger/better screw driver and a few taps with a hammer to drive it into the screw head a little.

How full is full enough? My manual just says add enough fluid if low.
My fluid is just below the very top of the window,buy below the molded in fill??? line?

If I add fluid and the warning light stay on, what should I look at next? The actual brakes and brake lines? (Delamination or not, I'm not looking forward to disassembling and removing the rear tire).

EDIT2:
Brake fluid is light/medium brown. Time to research flushing/bleeding the brake lines as well. :roll:

EDIT3: Short term
Bendy straw + little suction and gravity = Empty Master Cylinder
Light cleaning/wiping of inside
Topped off with the Dot3 I bought the other day.

EDIT 4: Rear Brake Wear Indicator is toward the end of its life. Could that be causing the brake warning to stay on?

Road about 2 miles upto about 25 mph. I had no problems stopping, but I obviously wasn't going that fast.

 

The brake warning is triggered by the fluid level switch in the front master cylinder. The float could be stuck or the switch bad.

Since you can readily see the level I'm not sure why they bothered. The switch on the rear of my Venture is bad so I just jumpered the connections to turn out the light. Need to fix it though as the rear has no inspection window.

Your rear is a drum brake. There is no warning indicator on it, just the wear pointer on the brake cam.

 

Yeah I meant the wear pointer is near max worn.

Gonna have to get prices, tools and find that in the service manuals also...

 

I would flush and bleed out the system with new fluid right off the bat. I'll also mention that I have problems with the wire connections on my 750 Seca making intermittent contact sometimes, resulting in a false brake warning light. Time to clean and tighten them (when I get some time).