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Hi. I am getting ready to change the break fluid in my S70. Since the hydraulic clutch shares the fluid with the breaking system, I reckon I need to replace the fluid in that as well. I use Motive Products system to replace the fluid. It is really great. The way it works is you put fresh fluid into the plastic bottle tha is then connected by a hose to the break fluid resevoir and pressurized using a built-in pump. Then, you just open each bleedr in turn and let the pressure push the old liguid out replacing it with new. I usually start with the longest run (rear right) and work my way to the shortest (front left). Last time I did it, I neglected the clutch. I don't want to neglect it this time. But, I don't know where the bleeder for the clutch is. If anyone knows, please let me know. Also, I am about to use Valvoline synthetic break fluid that says it exceeds DOT3 and DOT4. Id this ok to use? I think this is what I used last time?
Great holiday to all!
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Vladimir. '98 S70 base, 5-speed manual - his, '93 945 - hers,
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The clutch slave cylinder is on the top, front of the transmission, visible from the front of the engine compartment, just to the left of and below the air filter housing as you're facing the engine. On my turbocharged car, it helped to remove some of the intake air hoses. That will be the easy part....
I've used the same Motive Products Power Bleeder on my car ('99 S70 T5M), with good results for the brakes. But I've had tremendous difficulty bleeding the clutch fluid. It seems that, on my car anyway, typical pressure or vacuum bleeding techniques, including the use of the Power Bleeder, or a Mity Vac hand-held vacuum bleeder, or the traditional two-man method, would introduce plenty of air into the clutch hydraulics, rendering the car undrivable. It was only by accident that I found the solution to this problem when I last bled the clutch fluid. The first time I tried clutch fluid bleeding on my S70, it took me EIGHT HOURS before I did SOMETHING that regained pedal pressure, and I wasn't able to identify the solution. This time, I figured it out.
Only by pumping up the pressure in the Power Bleeder to about 20psi, which is about double what Motive Products recommends, was I able to force fluid through the clutch hydraulics without pumping ONLY AIR into the system. Even so, there was still some air in the fluid, but this would self bleed after a few pumps of a partially firm clutch pedal.
At any pressure much less than about 20psi, it seems that a valve somewhere within the fluid reservoir/master cylinder assembly would allow ONLY air into the lines. I've been able to replicate the problem and the solution on my car several times now, so I'm confident that it's not just some one time fix. For what it's worth, I've flushed clutch and brake fluid on perhaps a dozen different models of cars, perhaps as many as fifty times in total, so it's not just a question of inexperience on my part. There's something odd about the design of the S70 clutch hydraulics. So I'll be curious to hear if anyone else has shared my experience with this system, and can replicate the problem and the fix.
BTW, if anyone is of the impression that it's not necessary to flush the clutch fluid, keep in mind that the moisture that most brake fluids absorb will promote corrosion within the master and slave cylinders. On the '99 and later 70-series models (and probably other 99-and-later Volvos, as well), the slave cylinder is an INTEGRATED MODULE with the clutch throwout (release) bearing. When it fails, it will require dropping the tranny to replace. That's big bucks for labor, as opposed to putting it off for a few years by properly replacing your clutch fluid at regular intervals.
Lastly, regarding Vladimir's question about Valvoline synthetic brake fluid, there are two schools of thought about this. On the one hand, synthetic fluid doesn't absorb moisture the way that regular brake fluid does, so it's less likely that high-humidity climates are going to take their toll on hydraulic systems. On the other hand, because synthetic fluid doesn't hold moisture in solution, any water that does get into the system will tend to pool at the lowest point in a hydraulic system -- typically the brake and clutch slave cylinders -- thus PROMOTING corrosion. The solution to that is regular bleeding of the system, although complete flushing might not be necessary as often. That's why synthetic brake fluids tend to be popular for race cars, which tend to get bled between races, but they're still not being used in most OEM applications.
Hope that helps.
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Jim Rothe, '99 S70 T5M,
http://www.jimrothe.com/volvo/index.html
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Jim, thank you so much for the detailed and relevant reply. I would have been very upset if I rendered my car imobile by doing a simple bleed. I am now not sure if I want to go ahead with the clutch bleed. I know, I know, I should do it since it was never done on this car and I am approaching 50K miles. Last time I did the brakes I skipped the clutch. I am not very confident now about it with the consequences being a dead vehicle. I'll see what my gut tells me when I actually get down to do the job. I wonder what the service manual says about this procedure. I don't have a problem with pumping the power bleeder to 20 psi, but it just seems strange that the system would suck in air during bleeding. Just doesn't make sense. And what do you mean by self-bleed? Self-bleed where? Won't the air stay in the system forever? Or is the system not hermetically sealed?
Thanks again fir very valueable info!
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Vladimir. '98 S70 base, 5-speed manual - his, '93 945 - hers,
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"I am now not sure if I want to go ahead with the clutch bleed.... I am not very confident now about it with the consequences being a dead vehicle."
I understand your concern but, like I said earlier, I was able to replicate the solution a number of times. In fact, when I first figured out what was going on, I deliberately bled the clutch with lower pressure. Sure enough -- I got nothing but air bubbles out of the slave cylinder. When I pumped it up to 20 psi, it bled properly. At this point, I'm not afraid to do this simple job. You shouldn't be either.
"... it just seems strange that the system would suck in air during bleeding. Just doesn't make sense."
Tell me about it! BTW, that would be "blow," not "suck." ;)
"And what do you mean by self-bleed? Self-bleed where? Won't the air stay in the system forever? Or is the system not hermetically sealed?"
Think about it -- the clutch hydraulic lines have a short uphill run from the slave cylinder to the master. If a *small* amount of air were to get into the lines such that the pedal only had partial pressure, then you can be sure that those air bubbles would rise to the top of the lines and out to the master cylinder after a few pumps of the pedal. Any bubble of air that might still be left in the slave cylinder can be bled out with a brief crack of the bleed valve.
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Jim Rothe, '99 S70 T5M,
http://www.jimrothe.com/volvo/index.html
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Ok, you talked me into it. I'll try it. What is a good non-synthetic brake fluid to use for the S70? It calls for DOT4+, but I am not sure what that means. Most DOT4 fluids claim to exceed the standard. Is that the "plus"? Who knows? I can always get the stuff ftrom the dealer, but I don't usually like to get fluids from the dealer.
Best, and thanks again.
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Vladimir. '98 S70 base, 5-speed manual - his, '93 945 - hers,
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"Most DOT4 fluids claim to exceed the standard. Is that the "plus"?"
I think so. I'm using Castrol DOT 4+, commonly available at PepBoys and other not-so-horribly stocked parts stores near you. ;)
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Jim Rothe, '99 S70 T5M,
http://www.jimrothe.com/volvo/index.html
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I've been lurking on the fwd board sponging info for a while now. All of my posts have been on the rwd side before this. I believe the Valvoline Synthetic Brake Fluid is hygroscopic (absorbs water), because it is fully compatible with DOT3/4. DOT 5 fluid is the synthetic that I had always heard would not absorb water and posed problems because it forced water to the low points (calipers).
BTW, after bleeding rears on a 240, I can tell you the Motive Products Power Bleeder can push 30# on a system. Use the chains on the m/c before you go higher than 20#, just in case the grommets don't want to hold.
someguyfromMaryland
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