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  1. #1
    Member
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    Jul 2003
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    Phoenix Arizona
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    32
    Corvette(s)
    1987 coupe

    Default power steering reservoir overflowing 87 vette

    Has anyone experienced or know what would cause the power steering reservoir to start overflowing power steering badly fluid after driving 25 to50 miles on an 87 corvette?

  2. #2
    Member
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    Nov 2007
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    Virginia Beach, VA
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    41
    Corvette(s)
    1989 Black Z51 Coupe

    Default

    As long as the 25-50 miles weren't track miles, the only explanation that I can think of is that the ps reservoir was inadvertently filled up to the "hot" mark on the dipstick rather than the lower "cold" mark sometime in the recent past. Then 25-50 mile run was enough to then heat the ps fluid to point it expanded and overflowed.

    Really could use some additional information such as:

    1. When was the last time the ps fluid level was checked when cold?

    2. When was the last time the ps fluid was changed and what fluid was used to replace it?

    3. Did you lose steering response any time during the 25-50 mile run?

    4. What is the current cold level for your ps fluid?

    Thanks!

  3. #3
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    Corvette(s)
    1987 coupe

    Default ps fluid

    Thank you mr beachcomber for taking an interest in this what I think is a very unusual problem. The car is not used on the track.
    The ps fluid level was checked cold about 2 - 3 mo's ago and looked normal. When I think back, it could of been a bit above the cold line, but it wasn't concerning. I have never added ps fluid since I have owned it since 1998. I look at it about 3 times a year. I've never seen it leaving a puddle till now. I've put about 2 -3000 mi's a year on it. I have never changed the ps fluid and I believe it is the original fluid as I got the car with 55,000 mi and it just turned 90,000 mi. I've put about 35,000 mi on it since I've had it. I can see that it is real dark now when it hits the ground and looks like it should be changed.
    The steering during this run (yesterday) felt perfectly normal and I was surprised when I opened the hood to see the soaked leaking reservoir. I drove a total of 50 mi which is more than I normally drive it. It can leak good at 15 mi. I have noticed in the very recent past.
    I just checked the ps fluid just now cold and it is a half inch past the full hot line.

  4. #4
    Member
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    Corvette(s)
    1989 Black Z51 Coupe

    Default

    Thanks for answering my questions particularly about the no change in steering response. I was concerned that your steering rack might have been going bad.

    Since the ps fluid hasn't been changed since you bought the Vett and the previous reservoir level was more or less at the "cold" mark, I would check out the feeder hose from the reservoir to the ps pump to see if it's kinked or pinched thereby preventing the return flow in the reservoir from feeding the pump rapidly enough to keep from overflowing. (The 15 mile run w/overflowing shouldn't be enough time to expand all the fluid in the system, and since the last run caused ps fluid reservoir to puke out fluid, you shouldn't have a cold ps fluid measurement above the "cold" mark.)

    If the feeder hose is okay, then check the condition of the ps fluid. Some time in the past someone may have topped off the ps reservoir with ATF. In my experience with the C4 models, even original fill ps fluid doesn't sludge up even after 100K miles, but it does pick up material from the interior surface of the hose lines as they age. The ps fluid should be clear with a slight brownish tinge (from the rubber hose material picked up over time).

    Now would be a good time to change out the ps fluid for a fresh refill. The turkey baster method works well (for just the reservoir) in conjunction with disconnecting the ps hoses to and from the pump and steering rack. Your hoses shouldn't need replacement; however, be sure to check out their external and internal condition. (If someone in the past used the wrong fluid in the ps system, the internal surfaces of the hose(s) could be swollen limiting passage of the fluid.)

    After changing out the fluid, you'll need to bleed the ps system. Elevate the front end with floor jacks such that the front wheels are free and clear. Start the engine, and then slowly rotate the wheels from lock-to-lock 2-3 times. Then cut off the engine and check the ps reservoir. A frothy mixture of fluid and air indicates that air has been pumped out of the system. Allow the mixture to stand for about 3 minutes, and then repeat the same procedure again. Keep doing this until no more air is present in the system (as evidenced by a frothy mixture in the ps reservoir).

    After the air is purged from the system and the Vett is on level ground, add enough ps fluid to the reservoir to come up to the "cold" mark. Check the ps fluid when it's cold the next coupe of days to make sure that the fluid level remains at the "cold" mark, and you should be good to go.

    Good luck!

  5. #5
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    Corvette(s)
    1987 coupe

    Default

    Thanks for all of your input on this. I will be checking into what you have mentioned. It might take me a little while and I will let you know the out come of what I found.

    Thanks again,

    Rick

  6. #6
    Member
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    Dec 2008
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    texas
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    1,882
    Corvette(s)
    87 z-51

    Default

    The pump will also cause this.
    If the fluid is foamy when it over-flows, that is the pump cavitating and this makes the fluid appear to expand. In reality it is simply full of air bubbles from a dying pump. It may work normally but the bubbles tell the tale of what is to come. Worn out pumps do this.

    If the fluid had foam or suds when it did this, that's your problem. Replace the pump.

  7. #7
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    Corvette(s)
    1987 coupe

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    Thanks Boomdriver, I'll be checking for foam or suds or air bubbles.


  8. #8
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    Corvette(s)
    1987 coupe

    Default

    I have checked the fluid in the reservoir for any foaming, suds or bubbles while running and turning the steering wheel far left and far right a few times, with engine off and there was none. I checked the hoses going down to the pump and rack and there are no kinks of any kind. I got the turkey baster and withdrew the ps fluid out of the reservoir till it reads about a 1/4 of an inch below the cold full mark while sitting cold and all that I can think to do is watch it whenever the car is driven. I'll probably get a good run in sometime in the near future. I will work towards changing the fluid during this time. This is all I have for now.

    Thanks,
    Rick

  9. #9
    Gone but not forgotten John Robinson's Avatar
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    May 2005
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    Muncie, Indiana
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    1,609
    Corvette(s)
    1993 Polo Green Coupe

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    I think there is a pressure relief valve in the system somewere. When you turn the wheels full lock right or left and then release the pressure on the steering wheel do you hear a sound like air escapeing? I took a quick look in my manual but was not abel to see were that relief valve is in the system. If there is a valve and it is stuck and not allowing the system to relieve pressure that could cause the preassure to go back in to the reservior. And by the way my manual is very specific about the type of fluid to be used and how to flush the old out and replace with new.

  10. #10
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    Corvette(s)
    1987 coupe

    Default

    Thanks John, I will check that out.

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