79 2000 Brake compensator

[barnesjtsl]

Is there any easy way to check that the Brake compensator is working properly?

I'm not getting fluid out the bleeder on both rear brakes and I'm thinking it might be plugged?

I have it jacked up and resting on the axle with jackstands.

Any thoughts,

barnesjtsl

[DanD]

Crack open the line at the flexible hose going to the top of the differential. That should tell you something.

Most likely you have a frozen compensator, but I would assume if the compensator is shot, the flex hoses are due for replacement as well. It could be either, though.

[bbuckl]

I just dealt with a similar problem. I thought the compensator was bad so I used Mark's bypass kit. When I put it back together to bleed the rears, I found that my flex hoses going to the calipers were shot too. Ended up replacing all of the flex hoses just to be safe.

Brian
79 2000

[DieselSpider]

There are some that will replace the rubber lines every 5 to 10 years just on principle to prevent these occurrences. These issue will happen more often if you do not flush out your brake fluid replacing it with new fluid from a freshly opened bottle at least every 2 years.

Be mindful that some of the rubber formulations used on OEM spec rubber brake hoses and inside the master cylinders may not be 100% compatible with synthetic brake fluid so be aware of that possibility. I won the lottery on that one and had the rubber seals in a brand new master cylinder turn to putty a few months after getting flushed and filled with synthetic brake fluid instead of plain old DOT3.

[So Cal Mark]

synthetic brake fluid should only be used in race cars

[DieselSpider]

synthetic brake fluid should only be used in race cars

Non-synthetic is getting harder to find though. I almost bought some DOT3 and asked what made it Premium DOT3 to which they had no answer. Glad I read the Spanish label because there it revealed that the Premium DOT3 was Synthetic. Advanced Auto was so advanced that they did not have plain old DOT3 in the store and could not special order it either.

[KevAndAndi]

Amazon has a good selection of DOT 3 brake fluids. I bought the Mag1 Premium. It says nothing on the label or in the specs about being synthetic.

[DieselSpider]

Amazon has a good selection of DOT 3 brake fluids. I bought the Mag1 Premium. It says nothing on the label or in the specs about being synthetic.

I contacted Mag1 and the response from their tech (Charles Gade) was as follows:

"I would consider our Dot 3 brake fluid to be synthetic. It is not silicon based, like a Dot 5 brake fluid would be if that is what you are asking.
Thank you for your question."

So it gets harder to determine now since with some companies you can't go by the label and have to ask what it is. Some DOT3 labeled as Synthetic may be a Madison Avenue sell based on the ploy that technically old fashioned polyglycol mixed with glycol ethers can be considered a synthetic product however it is not the same as a Silicone Based Synthetic.

So now I'll be sure to look for polyglycol mixed with glycol ethers without any silicone to be safe.

[KevAndAndi]

After a little Googling I found the following two excerpts from two different sources.

On what "synthetic" really means:

Both synthetic and conventional brake fluids start from the same “polyethylene glycol” stock. But, to make synthetic brake fluid the manufacturer will “synthesize” the original base stock and make the molecules better and more consistent. They could make the chains longer or add other molecules to enhance the performance. Almost every synthetic brake fluid manufacturer does it different.

On the effect of silicone on rubber:

Another factor is the effect of silicone brake fluid on the seals found in standard brake systems. Ethylene propylene rubber seems to lose durometer (hardness) when exposed to certain silicone fluids. Although not the case with other synthetics, it is very true in the case of silicone. This results in a change in the size and an increase in the wear rate of all rubber components in the system.

As the Mag1 DOT 3 fluid lacks silicone, I don't think the "synthetic" designation is a concern. If anyone with more expertise than I (could describe most people on this forum) differs, than I would like to hear their perspective.

[DieselSpider]

I have a vague recolection of my Dad mentioning developing rubber formulations for brake systems on military vehicles destined for long term storage that would hold up to the silicone based fluids so they could be just fueled up and driven in the case of an national emergency. Even at 98 he was still sharp and kept current and was a treasure trove of accurate knowlege spanning from his schooling in chemical, electrical and mechanical engineering at MIT graduating with his Masters in 1927 at 21 till he died 77 years later in 2004. Before that he was apprenticing in Tiano Itally as a Vinyard Carpenteri while he was stranded there as a child where he learned to forge metal to make nails and tools for the carpentry work involved maintaining the vinyards (making barrells, vats, buckets and even stringed musical instruments) along with taking raw rubber and formulating it to vulcanize into gaskets and hoses for the vats and such along with make waterproof shoe soles and complete boots for the workers and villagers until the Great War ended and he could come back to the US. My Uncle (his younger brother) worked with him and ended up a designer of vulcanizing and other hot processing equipment for the rubber industry.

[RRoller123]

What a fantastic story and history! He sounds like a great fellow, led a full, rich life.