Water Pump Part 2 - inspection and measuring

Water Pump Part 2 - inspection and measuring


by

Tom Smith

 

It is a good idea to look things over during disassembly to see if there are any obvious problems. Things like a cracked or broken pulley, housing, or impeller. Also look over the bores for obvious wear and be sure and include the housing bore for the seal flange. Check your pulley groves for excessive wear also. Check for signs of a coolant leak, even if small. It might answer other questions you have had.

The drilled holes on the rear of the pulley are to balance it for longer bearing life and to reduce fatigue in the shaft so it does not break. It would be rare for a pulley to balance with none of these holes.

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Evidence that the seal was leaking. Probably becoming noticeable on the front of the engine.

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A couple of photos showing the housing a little cleaner. The side hole from the bore to the outside of the housing is for liquid to escape without getting into the bearing. The pump must be installed with this hole to the bottom.

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Assuming your pulley, hub, and impeller are in good condition the next thing is to take a few measurements. I first measured my bearing/shaft so I would have the information to identify the correct series for the replacement.

My bearing /shaft had the following dimensions. The bearing diameter was 1.181in or 30mm. (Standard size) The bearing length was 1.528in or 38.8mm. (Standard size) The shaft diameter was .6265in or 15.918mm (Standard size) The overall shaft length was 4.4125in The vane end shaft was 1.836in The pulley end shaft was 1.0615in

Then I measured the bores for the shafts and bearing. These are the most important measurements you will take, if you do not feel comfortable with your skill level here have someone take these measurements that is. Especially in the pulley and impeller. I wanted .001in to .002in interference fit between them and the shaft. In other words the bores should be slightly smaller than the shaft. That is what keeps them together. Too little and the pulley or impeller might slip or spin, or worse just come off the shaft. Too much and they could be stressed to a point that at high RPMS they might hatch (come apart due to centrifugal force and stress) Knowing the bore sizes makes it possible to order a bearing with a correct shaft size.

One more bore to measure is the one for the seal flange. Because it is a standard size bore it is not nearly as critical as the others but you do not want to be sloppy either.

I did a lot of searching and finally found John Crane, Inc, which is a company that produces seals. I talked at length to one of their technical reps, who recommend one of their seals, S106MAST, a ceramic seal with stainless components. He also recommended the Harold Bishop's HDRK CO, INC. IN Albany, Indiana. (765) 789-4406. I called Harold and gave him the measurements I made and he recommended the following shaft. W2446; shaft length 4.469; pulley end length 1.081; vane end length 1.859; shaft diameter 0.6267.

Harold had both the seal and bearing/shaft in stock and I had them in a couple days. I add that Harold knows his stuff and was eager to share his knowledge.

You might notice the shaft lengths are slightly different than the original. You will see how to deal with that in the assembly part of this series of posts.

The old and new shafts. Notice the rust on the impeller end of the old bearing. Not only was it failing but it could have possibly been avoided. Look at the new shaft and it has a groove around the shaft near the bearing. That groove will throw the coolant off and prevent it from following the shaft to the bearing.

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The new seal

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Following are a few measuring tools that might be used on a project like this and a little about using a caliper. Calipers, especially dial calipers, are quite inexpensive and even available in the $20 range. As handy as they are it seems to me to be an essential tool. This picture shows 1in to 2in and a 0in to 1in micrometers and a set of inside micrometers. These are generally used when a more accurate measurement in the range of as little as + or - .001in might be desired.

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This picture shows a digital caliper, a set of telescoping gages, and two sets of feeler gages. The telescoping gages are what are called transfer measuring tools. What that means is that they are set to fit the inside of a bore or groove and then removed and measured with a tool such as a micrometer or, less commonly, a caliper.

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A caliper could be a vernier, dial, or digital variety. The dial and digital are most commonly used. One of the most important things to remember when using a caliper is after making and recording a measurement to close the calipers to make certain it is still reads zero when closed. If it does not read zero the previous measurement may be invalid. It is also important for the jaws to be clean when setting the zero. One of the best and easiest ways to do this is to simply close the jaws on a clean piece of paper and draw it out while keeping a slight pressure on the jaws. A caliper is generally not reliably accurate to less than + or - .002 and then only if it is in excellent condition. The old one in the pictures is not that good. Because of that I am careful what I use it for.

Here are the four ways to measure with a caliper. It was interesting trying to hold the caliper while taking pictures and even though it may not be obvious, it is important to keep the caliper as square and perpendicular as possible when measuring.

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The last part of this three part article will cover assembly and one more tool that will be needed.