Step 8: Safety Overload and Check Valves

Move your cursor over the text boxes in the first photo. for part names, etc. The cylinder would normally be removed for a rebuild. But, this one is stuck very tightly. Remember how much difficulty there was in removing the ram nut in step 6. It screws to the cylinder, so the cylinder should be difficult to remove, too. It is not as easy as the video linked in step 3. I tried, but could not get it to loosen. There actually are no "O" rings or seals below the cylinder on this jack.  Removing it does not give access to any removable parts. I did notice some oil at the bottom of the cylinder appears dirty. 

There are two metal plugs in the body of the bottle jack unit. Two large screws are below them.  See the text boxes again.  This site warns NEVER EVER to open these. It also has a diagram of what is inside. (Scroll down to the middle of the web page.) The author's concern is that the small balls in the valves can be lost, and the jack would become useless. Get a shallow cardboard box with no holes in the bottom or a large pan and work inside of either one. If any balls roll away, they will be contained inside the box or the pan. Also, extra balls are included in my kit. Even if the balls were not included in the kit, precision steel balls can be purchased at a bicycle shop in a series of sizes. Check the link in this paragraph for the sizes normally used. The ball sizes in my jack are: 5/16 inch (7.94mm), 7/32 inch (5.55mm), and 5/32 inch (3.96mm). I measured them with a caliper through the plastic parts bag. I want to do as complete a rebuild as possible. Dirt may have found its way into the passageways where the balls are. The balls could also have rough surfaces through years of use.   

If I turn the jack body back and forth I can hear metal balls rolling inside passageways.  I drilled a hole in the center of each of the metal plugs.  Then I inserted a slightly larger sheet metal screw into the hole until the threads bound against the hole I drilled. I placed a pair of pliers under the head of the screw and pounded against the pliers with a hammer to pull the metal plug out of the jack's body.  I repeated the process with the other plug. New plugs are included in the parts kit. 

The second photo shows the bottle jack unit's body, but inverted so it was easier to hold while operating the camera.  The metal plugs have been removed. Both holes have a large screw inside them.  The one on the right is recessed so far that it is not visible.  It is the safety overload valve.  This valve protects the jack's seals from failing under a load heavier than the jack's rating.  When the safe range of the jack is exceeded, the safety overload valve opens like a pressure regulator to allow oil to return to the tank rather than entering the chamber for the ram. This screw has to be set so the safe level of pressure is not exceeded. In order to do that at home, I carefully turned this screw and counted by half-turns until it bottomed out.  My screw was set to 1 3/4 turns above or looser than the bottoming out point. When it is time for reassembly, I will turn the screw gently until it bottoms out, then I will back it off 1 3/4 turns. The safety overload valve should then be set very close to the original factory calibration.  One author noted that some jacks fail because the safety overload screw unscrews itself, which sets the jack's lifting ability to a much lower threshold, and the arm may not lift what you want to jack. I found this screw turned with enough resistance that it is not likely to shift its position by itself. That same author also said most safety overload screws are about two turns looser than the bottoming out point.   

The third photo shows the parts for the safety overload valve in the order in which they are inserted.  A new ball is included in the parts kit.

The fourth photo shows another special tool I made.  The screw for the check valves is quite tight.  I tried the largest screwdriver I had (3/8 inch wide blade) with a wrench on its square shank.  The blade on the screwdriver broke! The screw slot is 1/2 inch across the diameter of the screw and almost 1/8 inch wide. I bought a short bolt 5/8 inch in diameter.  It is #8 on the hardness scale. Near the end I ground the diameter down until it fit nicely inside the recess for the screw.  I kept a cup of cold water near my grinding wheel to avoid softening the bolt with heat. I ground a rough profile by sight. I moved the bolt to a vise and finished cutting the profile of the screw slot by means of a hand file. I checked the dimensions with a digital caliper.  When my improvised screwdriver fit the screw and its slot, I tapped on the bolt's head to be certain it had fully seated in the slot.  I used a wrench on the bolt head and the screw came out with no difficulty, at all.  I had tried to buy a large screwdriver, but could find none this large.  This improvised solution cost me $1.65 for the bolt and a few minutes of time. 

The fifth photo shows what was behind the check valve screw. See the text boxes for ball sizes. 
Oh boy. All the typical difficulties I somehow subconsciously know. Another compliment on great instructions! What a dismal item in the to/should-do list. <br><br>Well envisioned and made tools.
<p>Good indestructible. A real big help. I wasn't able to follow your instructions exactly since I don't weld, but I devised other techniques to get the job done. Except for opening the main bottle and ram. </p><p>I could not get the ram and bottle off my jack for lack of your special tool. So, thinking about the failure mode - mine wouldn't raise without some pressure on the arm, but it would lift my car and stay up - I decided that part was working OK and I would just rebuild the rest. I suspected the plunger.</p><p>I got the plunger off using some high-strength spectra (no stretch) dingy racing line. I could push the plunger down with a socket and then tied the line around the body of the bottle to hold it down while I got the C clip out. Stand out of the way in case it takes off unexpectedly. </p><p>Once the clip was off I covered the plunger with a heavy towel and just let things loosen until it popped off into the towel. No blood, no foul. </p><p>I then unscrewed the bottom half of the plunger, whacking my new 27 mm combo wrench with a good size hammer.</p><p>To reassemble I chucked the bottom part of the plunger into my lathe and used the saddle to press in on the top part until I could reattach the C clip. Then I screwed the plunger assembly back in place. </p><p> I center punched the metal caps and drilled them out with a 1/2 inch drill in a variable speed battery powered drill. I could turn the drill very slowly and once through I could just pick the remaining ring of metal out of the hole with a screwdriver or whatever. </p><p>Once the caps were out I cleaned out the metal chips and used my hammer style impact driver to remove the right (shallow) screw cap. It was screwed down all the way. The deeper screw cap was very loose. I think it had screwed itself out over the years. </p>
<p>Hey, https://www.instructables.com/member/RobM5/ took me here. He also did a instructable for a service jack. Yours is even more thorough than his. Thank you for that. And thank you RobM5 for being a decent guy.</p>
I try to look regularly at the recent Instructables and saw his floor jack power unit repair Instructable. I am glad you found the one I did. I was a little surprised that mine was not listed in the related Instructables. I considered posting a comment in which I would list a link to mine, but it seemed a little too much like shameless self-promotion. Thanks for your comment. I tried to be thorough because at the time I did mine there was very little on the topic available on the Internet.
<p>This was very interesting and i think the only one of its kind. I have 2 floor jacks that have been sitting around broken for over a year that im planning to repair soon. i thank you for the making of this ..</p>
<p>Phil - this process you documented is so awesome - many many thanks. Like you i am very much against throwing anything away and i only buy tools and cars etc made from those glory days after the war. of course, i am always chasing parts or making parts but in the end - when there is an end ha - the tool blows modern tools out of the water, looks wicked bad bc for some reason the old tools are just gorgeous and of course i am now intimate with the inner workings of said tool. Of course, since i have this great knowledge now - and might forget it all 10 years fropm now - i start fixing every similar tool i have, my family and friends have and of course i might even score a few new ones now that i am not intimidated by the repair. suffice to say, i have 5 blackhawk jacks ready to be bought back to their former glory plus lincolns, hein werner and a monster 10 T that i already finished which started the whole deal. i hope your still contactable bc i may have some questions after i get deeper into my blackhawk s4 which is disassembled now. talk about a badass jack - the 4 ton s4 has a light that shines up from the body and has a locking handle so you can leave it it up with a load and noone can drop it. its just a gorgeous art deco bad to the bone floor jack. thanks again man. eric in terrebonne oregon </p>
This is very well done and is exactly acting as was yours. <br>Thanks for such a well done description of the procedures <br>Will try rebuilding my 30+ year old floor jack
I apologize for not discovering your comment until now. Thank you for looking at this. I am glad it may be helpful to you. Let us all know how rebuilding your jack goes for you.
I just signed up with instructables in order to award you a high five for a most excellent article. Not only is this impressive for the clarity and precise language, but it demonstrated perfectly the steps with illustrations giving the detail to understand. Not an easy undertaking. Probably a lot more thought went into it than most people are capable of making. <br> <br>I very happily stumbled into this page because I acquired a floor jack this week without the instructions and since I follow warnings, looked on line for them after reading the warning: Fully read ALL instructions before attempting to use this Floor Jack. <br>Haven't found them yet but what a treasure this piece was to read! <br>Bravo! And I will be reading more of your articles. Your dad did a fine job rearing his son.I'm pround of you for him.
Thank you very much. I am glad you found this Instructable and it is useful to you. I believe I mentioned there are manuals on-line for some various hydraulic jacks.
Phil,aloha from the Big Island~ Thank you for taking the time to document what is in essence a labor of love...love of the environment and respect for your father...You are correct in assuming that many would just replace this with a cheaper import, and while I am an avid recycler myself, there are times when I have to ask what my time is worth....'Course with the economy as it is now, it is worth less and less so it is more worth taking the time and expending the energy to fix things rather than replace them. I have an OLD 3 ton Sears/Craftsman brand jack which won't go up and I suspect the piston/valve....Reading your instructable encourages me to dive in....I'll just need to come up with model numbers and search the net for parts. Thanks again and keep up the good work!
We spent ten days on the Big Island back about 2005 using a time share condo in Kona as our &quot;base.&quot; Our hosts have been there many times and showed us just about everything. That visit became the cause for <a href="https://www.instructables.com/id/Heavy-Duty-Nutcracker/">this Instructable</a> on building a nut cracker that can handle macadamia nuts without crushing the meats.<br> <br> Get in touch with <a href="http://www.blackhawkparts.com/">Blackhawk Parts</a> or someone similar. Blackhawk can probably tell you who made those jacks for Sears and can probably get the right parts kit to you.<br> <br> Thank you for your comment.
Hi Phil, <br> <br>Im a grade 9 student and im having trouble finding exactly what parts are used to make up a hand-driven hydraulic car jack. Could you prehaps help me? <br> <br>Thank you!
From your description you must have a bottle jack. I understand you are asking which parts kit you would need to rebuild the jack more than what parts go into a hydraulic bottle jack. I would click on the link I gave for Blackhawk parts and ask them. They are very helpful. Send any information you can find about make and model. Send some photos with your inquiry. If anyone can help you, they should be able to do so. Thank you for asking. If you are asking what parts go into the make up of a hydraulic bottle jack, they would be very similar to those in my floor jack, except there may be fewer steel balls. One of my steps shows an exploded diagram of a bottle jack.
great instructible Phil. Thanks for sharing it.
Thank you, Matt. I hope you can use it. I wish I had been able to say, &quot;This job is simple as A, B, C!&quot; But, it was a little more complicated than that. Still, a jack you would rebuild may be easier to take apart than mine was.
I had to read it and learned something new. Though we don't have a jack we did inherit a huge vice which I have no idea what you would use one that big for in the home..So I like to just see how things are put together. Thanks for the great instruction.
Thank you. A huge vise anchored to something very heavy or to something set into a concrete floor so it cannot move would have been a help for rebuilding this jack. I managed by bolting the bottle jack unit back into the jack's frame and using the frame for leverage. You may yet need to rebuild a jack one day. Thank you for reading my Instructable. I like to know how things work and to see what other people have done, too.
Nice instructible! I'm a hydraulic specialist and I don't think I could explain the procedure as well as you did!<br>Check out IFPS.org<br>Alan Hale<br>
Dear Alan,<br><br>Thank you for your gracious comment. I hoped someone like you might see this and comment, especially in case I might have given totally false information, and you would correct me. This is my first intrusion into hydraulics, other than replacing a couple of brake lines on a previous family automobile and bleeding air from the system afterward. As I mentioned in the Instructable and in response to a previous comment, I needed to rebuild my jack; but, could not find all of the information I felt I needed. I wanted to document what I did, should I ever need it again, and also make it available to anyone else in the situation in which I found myself.<br><br>Thanks again. I hope to run into you on this site again.<br><br>Phil
it is of little importance, but brake fluid doesn't make seals swell. i am currently taking an auto brakes repair class and you're thinking of antifreeze and tranny fluid. my instructor in his earlier year worked on mercedies-benz and he specifically said, if u put tranny fluid in the brake lines, the seals will swell, and u'll have to overhaul the entire system and replace the seals.
Thank you for the information. It was a warning I read in someone's post about hydraulic jacks. I once poured some power steering fluid into the braking system of my car absentmindedly by mistake and had to spend a couple of hundred dollars to get things made right again. Since that time I have been more on guard about what bottle I grab.
lol i bet that was fun :P and any one else reading this, liquids in ur car can not be mixed and matched! they r formulated and designed for different jobs, even if 2 different liquids are glycol based, there are different substances in some not found in others, like a seal swell additive.
As I said, it was an absentminded mistake.
perfect timing, I need to repair my father's jack. Also a super through instructable!
Thank you. I made it for people just like you. I wanted it to be thorough. As I mentioned, I had trouble finding good detailed information on the Internet and wanted to make available what I wish someone had published earlier so I could have made use of it. Please take notice of the mention I made that information about the size of the balls in the check valve (photo text boxes in steps 8 and 13) contains errors in the PDF version, but has been corrected in the on-line version of this Instructable. Basically, the smallest ball is used in the safety overload valve. The medium ball is the first ball to go into the iron block that is the base of the bottle jack unit. A short spacer (or possibly a spring) is on top of that, followed by the largest ball. There is another spacer or spring followed by the screw cap.<br><br>I always pray that my Instructables will be a blessing to someone who needs them. Thank you for letting me know about your need. Please report back when you are finished. I would enjoy hearing how it went for you.
Awesome, Phil!<br><br>I confess I did not read fully, this is a full super instructable.
Thank you, Osvaldo. It is good that you did not read all of it. This Instructable is for the person who wants to rebuild a jack. There is no reason to read every word until you are faced with a jack that no longer works. Then all of the details will be very important and very interesting. <br><br>There are very few helps available for the person who needs to rebuild a jack. I am hoping this will be found by those who need it. <br><br>Rebuilding my jack was more difficult than I expected from what I had read. I needed to make several special tools. Several times I thought I had encountered a roadblock I would not overcome. A couple of times I thought I had ruined a critical part and would need to send the whole thing to the junk.<br><br>Doing this took quite a lot of time over at least a week. Still, I am finding small, silly mistakes.<br><br>Thank you for looking.

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Bio: I miss the days when magazines like Popular Mechanics had all sorts of DIY projects for making and repairing just about everything. I am enjoying ... More »
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