Attention Welders - How Would You Weld this Hydraulic Pump, if at all?

[Jacob McCrea]

Folks,

I need some advice on how to weld or otherwise repair the hydraulic pump in the attached photo. It came off of an old tow truck's hydraulic system and was made by Eaton. A guy who lives near my shop asked me to weld it. It was welded once already, and if you look at the weld, you won't be the least bit surprised that it did not hold. I haven't been able to determine the exact type of metal it is. The inner part of the pump appears to have been cast, based on the texture of the surface. I would guess it is cast steel. I've never actually seen the crack as it's buried under the poorest weld bead I've ever seen.

I have mig, tig and oxy-acetylene equipment on hand, but am at a loss as to the best procedure. Any thoughts and guidance are appreciated.

Hydraulic Pump.jpg

[Al_C]

I think his best solution is to find a rebuilt pump. Maybe others will have differing thoughts, but I'd want to get rid of the existing bead and get down to the original surface. I'm not sure it's worth the labor involved.

[alv69]

I would grind away all the old and try to get it clean enough to tig weld, good luck.

[Mike N]

If the pump has a precision bore on the inside any welding might distort it enough that it wouldn't work so well anymore. In fact with that big glop of weld on the outside you might find some strange wear on the inside already. Depending on the material you might need to pre heat the part or weld with a special ductile filler or both especially if it's cast iron. Cast iron will crack if it's heated or cooled rapidly. Crown Alloys 44-30 cast iron mig wire would be a good choice for welding cast iron but a 2# roll might actually cost more than a rebuilt pump.

I would dis-assemble the pump and inspect the inside. The case might be distorted enough to be junk already. As noted above the next thing to do is to take a die grinder or something similar and grind the existing weld off to see what you are dealing with. But before that I would see how much a rebuilt or new pump would cost.

[Jacob McCrea]

No doubt, simply finding a rebuilt pump would be better, and I am sure it is at least half-junk based on the "tight spot" in the shaft's rotation. But for the owner, saving $100 is like one of us saving $1,000. I will cut and grind the old weld off and see what I'm actually dealing with. Thank you for the advice; further comments are welcomed and appreciated.

[UnhipPopano]

As a Toe Truck, there is a cost of "Business". In this case the three alternatives are to fix the old pump, replace the pump with the same model [Old Truck = Old Style Pump], or replace with a new pump.

To fix the pump, as discussed above, you would be best off to purchase a replacement part from Eaton.

We could also purchase a new pump from Eaton of the same model, if it is still available and it would be reliable and should last.

Or there are similar pumps that are out there that are not as expensive and may work.

All three of these alternatives will work. If you try welding the unit and fail, you will only eliminate the first alternative. But if you need to purchase wire or anything else, you will need to take that into account in the cost of the repair. If money is tight, then wasting it on a repair that will not last may be the most costly alternative of the three.

[NAZ]

It appears to be a garden variety Eaton hydraulic pump -- a throw away part. As stated above, there's a good chance it's not reparable -- cracks, warped, poor repair welding. I've got a great deal of experience welding castings and as a machinist I also have experience re-machining warped and damaged parts -- I wouldn't waste my time on this pump. Do yourself a favor and tell the guy to buy a new one.

However, if you are interested in spending your time learning how to repair a casting here's my suggestion. First do a spark test to determine if it's cast steel or cast iron. Go online to find videos of actual spark testing as it's better to see what they look like than to try to understand from a written description. You simply grind an area of the casting a watch the sparks. Cast steel and cast iron have very different sparks. If it's cast iron you'll be better off on a small part like this using pre-heat and post heat and stress relieving. But since it's junk anyway you could try using the cast steel method below.

You will have to grind out ALL the old weld material to get down to the original casting. You will need to "V" the crack so that you can fill it with 99% nickel filler using the TIG process. If the crack does not end you must drill a stop hole big enough to back fill with ni rod. The casting will be soaked with oil and contaminants deep into the poors and simply surface cleaning is not good enough no matter how hard you scrub. The part must be soaked in solvent, blown off with compressed air, and heated evenly with a oxy-act torch to ~200-degrees or so -- and probably more than once as ALL contaminants must be gone before attempting to weld it.

You'll need an IR temp gun and a needle scaler. You can usually get away with no pre-heat on cast steel but you must control the heat by making very short beads (about an inch long) and immediately use the needle scaler to stress relieve the weld. Don't let the area adjacent to the weld get over ~400-degrees and let it cool below 200-degrees before the next bead. Don't get in a hurry or you'll hear the dreaded "tink" of a crack you just created.

This is expensive (the nickel rod is ~$100 a pound) and time consuming but believe me, I've tried a number of methods and nothing works like the one I detailed above. Welding cast materials is not something typically taught in welding school. I spent many years welding in factories repairing cast piping and machinery and learned all the tricks from the gray haired welders. You will spend more repairing this pump (and not likely to succeed) than the cost of a new one from Northern Tool. But good luck and you may learn something along the way.

[Jacob McCrea]

I haven't turned down many chances to learn a new skill, but based on the good advice above I told this guy to buy a new pump. Cheaper ones go for about $125.00 on ebay and there was no reality where I could try to do it right and charge less than that.