Do you think your Citroën has contaminated hydraulic fluid ?

My little video yesterday showed you a simple test to do if the LHM system has a little brake fluid in it. Now I will tell you some of the tell tale signs to look out for when the system might be contaminated.

This may seem silly for a system that is marked properly on the hydraulic reservoir for what type of fluid it should take. But, many of these cars change hands numerous times. (just watch eBay for a few months and you will probably see the same car come up again and again with a different seller each time) There are just people out there who might toss something into the system before they realize what it takes.

The hydraulic system of the Citroen is composed of quite a few rubber components. In the early days, with the Citroën15/6 H and the early D Model, a rubber called EPDM was used when LHS2 , a form of brake fluid , was used.

Later, when they devised a rubber that would stand up to mineral based oil, they started to use Buna . A few other types have come along over the years as improvements in rubber manufacturing have been devised.

One thing I have to say here about EPDM compared to Buna in standing up to its respective fluids, is that EPDM stands up far better to brake fluid in the long run than Buna does to LHM . I say this because, when I take apart an old brake fluid sphere to rebuild the rubber diaphragm , it is always in good shape and still holding gas , sometimes almost 50 years on in many cases. (That is if it always had the proper fluid in it.)

The other thing is the EPDM was much less susceptible to molecular diffusion , or the loss of gas then the Buna .

The Buna on the other hand (if it is an original diaphragm ) has always turned to GOOP . The newer rubbers they have now hold up must better I must say, but that original Buna was not good in the long run.

I guess the point I am trying to make here, is that rubber for hydraulic use is designed to hold up to the specific fluid that runs through it. Pollute this in anyway, (and I mean it just takes only 1 to 2 percent of the wrong fluid in the system) and the rubber parts will start to deteriorate very quickly.

The way the system is set up, the parts effected first are those ones with the biggest surface area and the most fluid traveling across them. In the case of the Citroen , this is the diaphragms in the spheres . So, one of the first signs you will probably have is a ride that starts to deteriorate. Next, as the diaphragms blow out and gas from the spheres is injected into the hydraulic system, you will start to get air in the brake system as the gas is circulated through the system.

As the ride deteriorates and the brakes start to get air in them, the fluid level goes down in the system, as the entire sphere needs to be filled up with fluid at this point. You will also notice the hydraulic pump start to cycle with greater frequency.

The steering at this point no longer has any power assist!

Now hopefully the owner realizes what is happening before this situation happens, but if he doesn’t, then he is in for an expensive bill even if he does a lot of the work himself.

Next, I will cover what would be the most cost effective way to handle the above condition.

Later,

Denis

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