Brake Fluid - Dot 3 vs. Dot 5

[Archive]

Hi All,
According to my factory service manual, I should use DOT 3 brake fluid for my 98. 5 Ram. Anyone know if DOT 5 will work ok and if it will be any better than the DOT 3 ?



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98. 5 2500 4x4, QC, SB, Cummins ISB, Auto Trans, SLT, 3. 54 w/ LSD,
Horton Fan Clutch, Mag Hy-Tec transmission Pan, TransGo Performance Shift Kit,
Warn Front Receiver, K&N Air Filter, Van Aaken CPC, 275 HP Injectors,
HVAC Boost Elbow, Westach Boost/Pyro and Trans Temp Gauge

 

[Archive]

Phil,

DOT 5 does not mix with DOT 3 or DOT 4. The proper way to switch to DOT 5 would be to rebuild the hydraulic system. Early formulations of DOT 5 caused premature failure of rubber brake parts but this supposingly has been fixed. DOT 5 requires very careful bleeding to eliiminate air bubbles. DOT 5 does not absorb water so would be good for a weekend/show car. I would stick to the DOT 3.

 

[Archive]

Ok, sounds like DOT 5 is out since it's a silicon based fluid and I would need to get rid of all the DOT 3 that is currently in there to use it.

How About DOT 4 ? From the quick scan of the net (ain't it a wonderful thing), it looks like DOT 4 is glycol based (like DOT 3), absorbs less moisture, and has better heat tolerance. If I blow all the DOT 3 out of the lines, could I put DOT 4 in ?

Anyone else out there done this ?


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98. 5 2500 4x4, QC, SB, Cummins ISB, Auto Trans, SLT, 3. 54 w/ LSD,
Horton Fan Clutch, Mag Hy-Tec transmission Pan, TransGo Performance Shift Kit,
Warn Front Receiver, K&N Air Filter, Van Aaken CPC, 275 HP Injectors,
HVAC Boost Elbow, Westach Boost/Pyro and Trans Temp Gauge

 

[Archive]

Phil,

I believe that you can safely mix DOT 3 and DOT 4 brake fluids. The DOT 4 has a higher boiling point than the 3. DOT 4 would be for someone who is in the mountains a lot or some other situation where the brakes are used frequently. If this applies then it would be better to flush the system which is a good thing to do periodically anyway.

 

[Archive]

I use Motul 600 on both my Viper and my Cummins. Dot 4 with 585F dry and 421F wet boiling points. It is fairly hygroscopic so must be changed more frequently than regular Dot 3. This stuff is magic! I have never had brake fade or boiled the fluid on either vehicle. Nice safety margin for those long downhills especially when heavy towing. $9. 95 a pint but how much is stopping worth?

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2000 Qc LWB 6Sp 3:54 LSD, + all the options except leather, BD Stage ll Injectors, Boost Module, Boost Elbow, K&N,
BD E-Brake with Shifter Control, ISSPRO EGT and Boost Gauges, Transfer Flow 50 Gal. Alum. Fuel Tank, Line X
16K Hijacker Double Rocker, Pulling a 35Ft. triple slide Spinnaker 5vr.
with every option available.