What is Cavitation? I will google. . .
Power steering flush after noise
- Thread starter cary
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bought the gal of Mobil DTE24 today, around 15.00 at Grainger's.
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I found this explanation, It’s basically the fluid boiling on a microscopic level in small areas around the vanes in the pump;
>Classical cavitation occurs when the absolute pressure of a moving liquid is reduced to, or even below, the vapor pressure of the liquid in the impeller eye. Bubbles are formed as a result of this pressure drop. Lower pressures in the impeller eye are caused by variations in velocity of the fluid and friction losses as the fluid enters the impeller.
>The bubbles are caught up and swept outward along the impeller vane. Somewhere along the non-visible side of the impeller vane, the pressure may once again exceed the vapor pressure and cause the bubbles to collapse.
>Implosions of these vapor pockets can be so rapid that a rumbling/cracking noise is produced (in our case the pump is small and high speed so, it happens so fast that it sounds like a groan). The hydraulic impacts caused by the collapsing bubbles are strong enough to cause minute areas of fatigue on the metal impeller surfaces. Depending on the severity of the cavitation, a decrease in pump performance may also be noted.
I have never seen a Toyota pump with obvious cavitation damage, they are pretty tough. The most common cause is low fluid causing the pump to suck air. If the reservoir is full and there are no leaks then the vapor (air) is forming in the pump. Anything that causes the vapor pressure (boiling point) of the pumped liquid to be reduced will make it worse. The most obvious cause is heat, by pumping fluid it’s heated, higher pressures equals more heat. Anything that causes the pump to pull the fluid in, like a restricted/kinked line between the reservoir and pump, clogged screen causes the fluid to be under a vacuum lowering it’s vapor pressure.
Oil is a good fluid for this application it’s very hard to boil, but some additives may not have as high of a boiling point, this is why I am going to try a cleaner oil. Cavitation is assonated with extreme heat in the bubble where it happens, if there are additives present that cant take the heat, they will be burned turning the fluid black and they will be deposited in the system in the form if varnish further clogging it up.
My system is quiet, except when pushed hard in hot weather. Once after picking my through a rocky wash the pump was groaning and complaining, I quickly opened the hood and saw a little fountain of fluid from the vent hole in the cap! After idling for a couple of seconds it stopped and a minute or so later the pump shut up, only lost maybe a teaspoon, after it cooled, the level looked good on the stick. But, that explains the oil I have around the cap after hard, hot wheeling trips.
>Classical cavitation occurs when the absolute pressure of a moving liquid is reduced to, or even below, the vapor pressure of the liquid in the impeller eye. Bubbles are formed as a result of this pressure drop. Lower pressures in the impeller eye are caused by variations in velocity of the fluid and friction losses as the fluid enters the impeller.
>The bubbles are caught up and swept outward along the impeller vane. Somewhere along the non-visible side of the impeller vane, the pressure may once again exceed the vapor pressure and cause the bubbles to collapse.
>Implosions of these vapor pockets can be so rapid that a rumbling/cracking noise is produced (in our case the pump is small and high speed so, it happens so fast that it sounds like a groan). The hydraulic impacts caused by the collapsing bubbles are strong enough to cause minute areas of fatigue on the metal impeller surfaces. Depending on the severity of the cavitation, a decrease in pump performance may also be noted.
I have never seen a Toyota pump with obvious cavitation damage, they are pretty tough. The most common cause is low fluid causing the pump to suck air. If the reservoir is full and there are no leaks then the vapor (air) is forming in the pump. Anything that causes the vapor pressure (boiling point) of the pumped liquid to be reduced will make it worse. The most obvious cause is heat, by pumping fluid it’s heated, higher pressures equals more heat. Anything that causes the pump to pull the fluid in, like a restricted/kinked line between the reservoir and pump, clogged screen causes the fluid to be under a vacuum lowering it’s vapor pressure.
Oil is a good fluid for this application it’s very hard to boil, but some additives may not have as high of a boiling point, this is why I am going to try a cleaner oil. Cavitation is assonated with extreme heat in the bubble where it happens, if there are additives present that cant take the heat, they will be burned turning the fluid black and they will be deposited in the system in the form if varnish further clogging it up.
My system is quiet, except when pushed hard in hot weather. Once after picking my through a rocky wash the pump was groaning and complaining, I quickly opened the hood and saw a little fountain of fluid from the vent hole in the cap! After idling for a couple of seconds it stopped and a minute or so later the pump shut up, only lost maybe a teaspoon, after it cooled, the level looked good on the stick. But, that explains the oil I have around the cap after hard, hot wheeling trips.
So the mobil DTE 24 is now in the system. I did a full flush of the Synth. ATF. I purchased some clear 3/8" tubing, a 3/8" bolt to use as a stopper and a 3/8" brass barbed union. I used a small section of tubing and the bolt to plug the return nipple to the tank. The rest was attached to the return line with the union and the opposite end placed into a bucket. I then poured in the new as the old was dumped into the bucket. It took almost three quarts to get the job done. I had my wife inside the truck turning the wheel to get both sides of the gear box.
The pump seems quieter and there seems to be a little less effort needed to turn the wheels. I have a 800 mile drive ahead of me this week so if this is a mistake I should find out rather quickly.
The pump seems quieter and there seems to be a little less effort needed to turn the wheels. I have a 800 mile drive ahead of me this week so if this is a mistake I should find out rather quickly.
300 miles today, everything seems to be running smooth.
I've been meaning to post on it. I love the stuff. Performs well in the cold and everything seems to work just a little better than the M1 synth ATF at a nice savings. I bought the gallon jug at Graingers but saw it in quarts there just this week in Utica.
I'll be using this from now on.
Probablyt have 3k on it now
I'll be using this from now on.
Probablyt have 3k on it now