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Ferrari 355, 360, 550, 575, 612 Rebuild Water Pump


I had a weird rumble and some dribbles out the weep hole of my water pump on my Ferrari 360 so while I was in there for a belt change, I decided to do the water pump rebuild.

The water pump on a Ferrari 360 is unusual in that to repair it, the bearings and seal are replaced instead of just replacing the entire unit. Rebuilding the water pump isn't trivial. It requires some specific tools, like a press (2 ton minimum) and suitable dies (30mm socket worked for me) to press out the existing bearing and seal and install the new ones, and a Ferrari specific tool (PST-01) to install the seal. 

The special tool is required because the seal (G in the diagram) has to be pressed into place on two surfaces. The body of the water pump and the impeller shaft. In between is a fragile seal made from ceramic and plastic that is easily deformed, crushed, broken, or shattered. The special tool keeps the stress off the seal and on the metal surfaces of the seal so that both are pressed down to the right depth at the same moment.

The tool is rather simple but requires a tight tolerance. Since those tolerances, and the PST-01 tool are unavailable, it has to be designed and built before the seal can be installed.

From what I can figure, it looks like the shaft seal has to end up being on the same plane as the back of the impeller. The body seal has a stop built into the body where it ends up. The difference between those two heights is also the distance between the shaft seal pressing surface and the pressing surface of the body seal. By measuring the above diagram, it looks like about half an inch. A good starting point.

To make the tool, I'd like to just 3D print it. That's my favorite way to make things. If plastic isn't strong enough, I can make one out of aluminum either with my CNC or metal lathe. The simple way is to just print it.

The question with plastic is always "Is it strong enough?" A lot of force is needed to press the seal into place. How much can a plastic tool stand before deforming? How much force can the seal stand before deforming? If the plastic tool can handle more than the seal, then it should be fine.

To find out, I made a test article with similar dimensions and ran up the pressure on the press until it failed. The seal started to deform at 1250 lbs., and the plastic didn't deform until 2500 lbs. The plastic passed.

Here's the test article in the press.

The next step was to figure out what the exact dimensions are for the PST-01 tool. Before I could do that, the old parts had to be removed and the new bearing installed.

Disassembling the water pump started with removing the impeller. Once I had that off, I could see what was wrong. The bearing was still fine, it had a little play but didn't seem bad enough to cause the rumble I heard. The seal was a different story. I'm guessing the previous rebuild of the water pump was done without the benefit of the PST-01 tool and had cracked. It was leaking very slightly as the area behind the seal, by the weep hole, had a lot of crystals of coolant and corrosion that indicated it had been leaking for a long time, probably since installation. 

I know the water pump had been rebuilt before because the previous tech had tried to pry the pulley off the shaft of the water pump using a pry bar or something similar against the housing. It left deep gouges in the surface but no damage to the structure. I used a gear puller. Came off without a struggle. It's always good to have the right tools for the right job.

The shaft of the bearing where the impeller sits was missing all the chromium coating and was worn from the seal slipping on the shaft. This might be the cause of the rumble.

Here's the old bearing. The impeller attaches to the left side. Note it's missing the chrome coating.

Removing the bearing required about 1,250 lbs. of force and a 30mm socket as the die. The seal required about 750 lbs. of force and came out in pieces. No matter, it's a one and done part. It's going to be replaced so count on buying one.

After disassembly, the water pump housing was intensively cleaned and the bore and seat where the bearing sits, gently sanded with 800 to remove any corrosion and scratches from previous installations. 

Parts of a Ferrari waterpump rebuild.

Before pressing in the new bearing, everything was carefully cleaned once again and a thin layer of grease was added to the bore of the housing. I added the grease to help the new bearing go in and when the time comes again in the future, to remove the bearing from the housing next time. 

Here's the new bearing ready to be driven into the housing. A 30mm socket is used as a die since it easily fits around the shaft and contacts the edge of the bearing. A 30mm socket fits perfectly into the bore of the housing.

The bearing has to be pressed in all the way to the back stop of the housing to clear the groove for the slip ring that secures the bearing in place. Before starting this procedure, be sure the housing is clean to bare metal where it stops or it may be difficult to press the bearing in all the way. There should be no gap between the bearing and the stop when examined from the impeller side of the housing.

The slip ring went in easily. The bearing was set.

Once the bearing was in place, I could measure the distance between the stop for the seal and the surface where the impeller sits. That's the difference in height between the outer housing and the inner shaft sealing surfaces.

Here's the impeller side view of the housing before the bearing is installed.

I found a picture of the PST-01 tool on the internet and it gave me some insight into what the designers of that tool were trying to do.

Here's the PST-01 tool.

Note that it has a slight raised ring on the shaft seal surface. It looks like that protrusion stops the seal from going down to the seat of the impeller by just a tiny bit. I'd guess that the reason for the raised ring is to prevent the shaft seal from going all the way down to the seat, leaving just a tiny bit so that when the impeller is installed, the seal will be pressed the last bit and be tight against the impeller. A little complication.

Once I had the dimensions and a picture of the old tool, I could proceed with finalizing the tool design.

Here's the sectional view of the tool.

Note the raised ring in the center of the shaft seal press area. I chamfered the top a little to help concentrate the force and because it looked better. The inner chamfer strengthens the outer housing seal area and the fillet along the join between outer and inner seals helps reduce the chances of cracking.

Here's the full image.

The tool was printed with 0.2mm layers, 8 layers on top, bottom and sides, and 80% infill. I used Amazon Basic Black PLA for filament and a Prusa MK3S+ printer.

I bought my water pump kit from ( A label with important instructions was included on the bag that held the seal.

Unfortunately, neither the PST-01 tool, nor the Three Bond 1311 sealant were available, anywhere. Frankly, I couldn't even find a reference to Three Bond 1311 so it must either be a misprint or it existed 100 years ago. Well, I made the PST-01 tool and went with an old favorite: Permatex 22071 Water Pump Sealant. It's really goopy and is easy to work with.

I'm going to suggest to Ricambia that they update their label.

Before I pressed the seal, I applied the Permatex to the inner shaft surface and the top edge of the outer seal where it presses to the housing stop. That's a 90 degree angle and that's the best place to seal something. The part of the seal that is pressed into the housing itself is coated with what looks to be red threadlocker. I left that uncoated.

Everything lined up very nicely and the seal was ready to be pressed into place.

As the seal went in, it made sounds like it was sticking and popping into place, probably from the red threadlocker but after the first bit, went in smoothly all the way to the stop. The pressure was under 1,000 lbs. the whole way down. I made sure it was driven home by bringing the pressure up a bit to around 1,200 lbs. with no additional movement. The seal was in place.

Here's the picture after the pressing.

It's difficult to tell from the picture but there's about 0.5mm seal sticking up over the top of the shaft seat, as designed. Torquing the impeller would push the seal down the remaining bit and make sure it's in solid contact with the impeller. 

I used blue Loctite on the impeller nut threads. I hate Loctite but in a situation like this, it would be very bad for the nut to loosen up inside the water pump. The Loctite will help keep it in place.

Since the nut that holds the impeller is on a free spinning shaft, and there's no safe way to grab the shaft so that the nut can be torqued to 25nm's, the solution is to use two nuts on the pulley side, tightened together, and grip one of those nuts in the vice.

I got lucky and found two of the proper size nuts in my junk drawer.

Here's the finished water pump with impeller, ready to go.

One note on the pulley side. I wasn't able to get the Woodruff key out of the old bearing so I had to order one, and pay an additional shipping fee. I suggest paying the $1.28 or whatever it was up front and plan on replacing that woodruff key.

Overall, this was a bit of a challenge as a DIY project due to the unknowns of making a tool and using it for the first time. This job requires a press of at least 2 tons. I say 2 tons as the job requires a max of 1,250-1,000 lbs. pressure but it has to be done carefully. Having a press with just enough capacity would make it difficult to tell when the bearing or seal was seated properly. Having plenty of capacity makes it a lot easier to do a job like this. 

I've uploaded the model for the PST-01 tool here:

Epilogue: I was able to get the Woodruff key out of the old bearing by placing it in a vice and squeezing one edge of the key until the other edge popped up. It damaged the key in the process but was still usable with a couple of passes of a fine metal file. I still suggest spending the $1.28 and getting a new one though. It is a Ferrari afterall.


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