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Brake system maintenance - three questions

1996 Grand Caravan with ABS, 3.3L V6, 152k.

Am I correct that Dot 4 brake fluid is equivalent to Dot 3 - with the added advantage of higher boiling point? Is there any downside to using Dot 4, other than a small additional cost? Seems like the cost difference is irrelevant compared to the safety margin to reduce the chance of boiling the brake fluid on a long downhill in hot weather, or - as in a recent puzzler - heating from the exhaust system. Or is Dot 3 really just fine for most cars?

Either way, I’m going to flush the system with new fluid (and replace old parts as needed), it’s definitely due. Neither my owners manual, nor the factory service manual, gives a capacity for the entire system. Ditto the Napa store. I’m guessing it’s in the range of two quarts. I don’t want to buy a full gallon only to let it sit in the garage, but if I need three quarts, I may as well buy the gallon. Can anyone suggest either where to find the capacity, or have a ballpark approximation for what the system will need?

Also, is there any benefit to flushing the system BEFORE replacing wheel cylinders to keep old fluid out of new parts? That makes sense to me, even if it uses extra fluid.

So:
#1: Dot 3 vs Dot 4
#2: capacity
#3: which comes first: flush or new parts

Thanks all!

If I’m flushing the brake fluid and replacing w/new anyway as part of installing a new wheel cylinder or something, I always flush the old fluid out while the old parts are still installed. Then I install the new parts and proceed to the bleeding process. I’m not sure if that’s the best way, but it has always worked for me. And it does seem like it would keep the new parts cleaner.

Dot 3,4 not an issue…
About a liter, 1.5 maybe…
Flush it DURING the parts replacement, not before or after…Just bleeding the restored system does a pretty good job of flushing it…The brake lines themselves hold very little fluid…The master cylinder and the calipers hold the bulk of it. Now if you have ABS, there is another pint stored in there and a service manual should be consulted as the ABS system has a pump and accumulator that needs to be purged…

I just did a full flush on my 2000 Caravan and one qt is enough. I just empty the reservoir with a syringe/baster and then fill up and do the 4 wheels the old school way.

I say “synthetic” DOT 3 priced the same as regular and that is what I got.

@Caddyman:

Flush it DURING the parts replacement, not before or after
That makes perfect sense, thanks. Re: abs - I do have the big factory manual plus supplements so I'll study that carefully about purging that part of the system. That's something I have no experience with yet.

@galant: Thanks. I’ll see what I can do with suctioning the m/c, but that’s recessed so far I’m not sure I’ll reach it. I do have a baster for this purpose, may try a siphon if the baster won’t reach, though I’d guess your 2000 is probably located the same place - it’s the same body config.

I discovered that the driver side drum is rusted on, no doubt from having been parked for five years. Will work on that tonight. I have already sprayed the center opening with PB Blaster…it’s not the shoes holding due to E-brake or adjustment, the drum didn’t budge at all. Passenger side came off easily. I’ll try again tonight, spray / tap / spray /tap/ spray / get BIG HAMMER.

My setup was a hose and a syringe and that is how I got in that spot. You can get 6 inches of rubber gas line and attach it to your suction device. I think the part stores have something for suctioning, but my store said they were out of it.

The drums could be a pain. My 05 Camyr’s were stuck, and that is in CA with no rust. I did not have the time to get them off and they work just fine. Some other day, or maybe I will see if any store around here offers free brake inspection. I am not a big fan of working on drums anyway. I find the adjuster annoying.

@galant
I’m also in CA (foothills) but the problem is that this car had been parked, inexplicably, for five years outdoors where we get abundant winter rain. I recently bought this car. The rust could be considerable, but I’ve only just begun…too early to tell what my chances are.

I was already thinking about the baster plus hose idea, thanks for the confirmation on that.