DOT 3 & 4 brake fluid

[WyrTwister]

Is it OK to use DOT 3 & 4 fluid in the master cylinder reservoir of a 1991 Chevy Caprice ? Will it " mix " OK with the " older " specifications of brake fluid ? Thanks , Wyr God bless

 

[demarpaint]

If DOT 3, DOT 4, or DOT 5.1 was in there before it will mix.

 

[WyrTwister]

What DOT spec brake fluid did Chevy use in 1991 ? Thanks , :-)

 

[mechjames]

dot 3 was what was used

 

[BHopkins]

DOT 3 and DOT 4 are 100% compatible. You can use DOT 3 or DOT 4 anywhere DOT 3 is specified. However, DOT 3 should not be used where DOT 4 is called for. DOT 4 meets higher dry and wet boiling points than DOT 3. Although your '91 Caprice may never benefit from the benefits, you may feel totally safe in using DOT 4 in it.

 

[Ducked]

Originally Posted By: WyrTwister

What DOT spec brake fluid did Chevy use in 1991 ? Thanks , :-)

Sounds like you're saying its on the original fill. If thats the case, you shouldnt be wondering whether it'll mix with new stuff, you should be flushing and changing it completely. In fact you should probably just change it anyway. Personally I'd use DOT3 cos here its about 2/3 the price and you'll use quite a bit to flush and change the whole system.

 

[Wolf359]

Originally Posted By: BHopkins

DOT 3 and DOT 4 are 100% compatible. You can use DOT 3 or DOT 4 anywhere DOT 3 is specified. However, DOT 3 should not be used where DOT 4 is called for. DOT 4 meets higher dry and wet boiling points than DOT 3. Although your '91 Caprice may never benefit from the benefits, you may feel totally safe in using DOT 4 in it.

The only issue with Dot 4 is that it tends to be more hydroscopic than Dot 3 so you need to flush the fluid more often. Mine uses dot 4 and the manufacturer recommends fluid flushes every 2 years. Lots of cars from the 90's never recommended an interval although it was always a good idea as water will eventually rust out the the lines and other parts inside your braking system.

 

[WyrTwister]

Well , after reading on this forum , I have been using the turkey baster , from time to time . Bit there is probably some of the original fill . Just got back from giving our Daughter a lift home , from work . ABS lite did not come on this time ! :-) Praise the Lord ! :-) Wifey is out of town visiting oldest Grand Daughter . Will try to flush the system when She gets back , & can help . Hope the little Bleed nipples are not rusted solid ........... Thanks , all , :-) Wyr God bless

 

[JLawrence08648]

Hygroscopic, not hydroscopic.

Originally Posted By: Wolf359

[quote=BHopkins] The only issue with Dot 4 is that it tends to be more hydroscopic than Dot 3 so you need to flush the fluid more often. Lots of cars from the 90's never recommended an interval although it was always a good idea as water will eventually rust out the the lines and other parts inside your braking system.

 

[Ducked]

Originally Posted By: WyrTwister

Well , after reading on this forum , I have been using the turkey baster , from time to time .

Presumably not reading (or at least not believing) the bit where it says the "turkey baster method" is pretty useless. I doubt its completely useless, since it may protect your master cylinder a bit, but its likely to leave some wet fluid in the extremities where it can cause corrosion and interfere with braking.

Originally Posted By: WyrTwister

Wifey is out of town visiting oldest Grand Daughter . Will try to flush the system when She gets back , & can help . Hope the little Bleed nipples are not rusted solid ...........

You don't need help (unless your wife is good at freeing up rusted bleed nipples, which is a pain). Wives may be different (no experience) but having tried girlfriends in the brake bleeding role I'd say it isn't worth the collateral hassle. There are several ways you can bleed brakes solo. Easiest is probably a simple gravity bleed, though I personally favor using an enema syringe for more pressure and control.

 

[WyrTwister]

Originally Posted By: Ducked

Originally Posted By: WyrTwister

Well , after reading on this forum , I have been using the turkey baster , from time to time .

Presumably not reading (or at least not believing) the bit where it says the "turkey baster method" is pretty useless. I doubt its completely useless, since it may protect your master cylinder a bit, but its likely to leave some wet fluid in the extremities where it can cause corrosion and interfere with braking.

Originally Posted By: WyrTwister

Seems to be doing a little good , since the ABS lite is coming on less often . I have done brake work many times ( starting back in the late 1960's ) & Wifey has helped bleed the brakes many times ( since the 1980's ) . Think we will be good in that area . Wifey is out of town visiting oldest Grand Daughter . Will try to flush the system when She gets back , & can help . Hope the little Bleed nipples are not rusted solid ...........

You don't need help (unless your wife is good at freeing up rusted bleed nipples, which is a pain). Wives may be different (no experience) but having tried girlfriends in the brake bleeding role I'd say it isn't worth the collateral hassle. There are several ways you can bleed brakes solo. Easiest is probably a simple gravity bleed, though I personally favor using an enema syringe for more pressure and control.

Have heard of gravity bleeding of the brakes . Was / am some what cautious about that . Have this cheap plastic transfer pump . Wonder how it would work ? https://www.harborfreight.com/multi-use-transfer-pump-63144.html Thanks , :-)

 

[WyrTwister]

https://shop.advanceautoparts.com/p/valvoline-dot-3-and-4-synthetic-brake-fluid-32-oz.-601458/7080002-P?navigationPath=L1*14924%7CL2*15037%7CL3*16113 I used some of this , this weekend . Could someone please explain DOT 3 & 4 . I would think it would be either / or ? Someone said DOT 4 was more hygroscopic . Not sure if I want that . Would that apply to this Valvoline product ? Thanks , :-)

 

[CT8]

Originally Posted By: WyrTwister

Well , after reading on this forum , I have been using the turkey baster , from time to time . Bit there is probably some of the original fill . Just got back from giving our Daughter a lift home , from work . ABS lite did not come on this time ! :-) Praise the Lord ! :-) Wifey is out of town visiting oldest Grand Daughter . Will try to flush the system when She gets back , & can help . Hope the little Bleed nipples are not rusted solid ........... Thanks , all , :-) Wyr God bless

The turkey baser is a 100% waste of time.

 

[skyactiv]

DOT 4 is cross compatible with DOT 3 brake fluid. Some brake fluids might be labeled saying both DOT 3 and DOT 4 just like some oils have been labeled API SM, API SN. I'd have no problem using a store brand brake fluid such as Supertech DOT 3 in that vehicle. Cheap at Wal-Mart at $4.XX a quart. That is what I used when I maintained my elderly neighbors Chevy Colorado before I moved. I use a turkey baster and a home made one man brake bleeder. You don't need to gravity bleed and get all crazy.

 

[skyactiv]

Suck out the old fluid in the master cylinder resivour with the turkey baster and add fresh fluid before flushing.

 

[Wolf359]

Originally Posted By: JLawrence08648

Hygroscopic, not hydroscopic.

Originally Posted By: Wolf359

[quote=BHopkins] The only issue with Dot 4 is that it tends to be more hydroscopic than Dot 3 so you need to flush the fluid more often. Lots of cars from the 90's never recommended an interval although it was always a good idea as water will eventually rust out the the lines and other parts inside your braking system.

Thanks. It's one of those words that's not in spell check and I was too lazy to look it up. As for flushing the fluid every few years, the higher you go up, the more frequently you're supposed to do it. Even though it's a sealed system, it naturally absorbs moisture through the rubber and through the calipers just from heating and contracting.