Technical 850 spider water pump rebuild
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Technical 850 spider water pump rebuild
Moved to Other Fiats as the 850 doesn't have its own section ... yet!
Ex Fiat Dealer Tech in the 70's here.
I've rebuilt a few of these water pumps many years ago - not difficult to do, just gotta be careful not to break anything...
A quick search shows www.midwest-bayless.com in the U.S. stock a rebuild kit and you can see this includes 2 x seals, 2 x bearings, a couple of large O rings and a gasket.
The rebuild procedure is usually well covered in any decent shop manual, but in case you haven't got one, here's what I can remember.
Basic procedure is :-
Remove waterpump from engine
Remove fan housing, fan and belt drive pulley. Also remove the woodruff keys (shaft keys).
Clean up each shaft end outboard of the bearings, this makes it easier to open up the pump.
Remove end plate (4 x 10mm headed bolts). Be very gentle with this, don't use a hammer and chisel or pry too hard. I'd suggest soaking the gasket in solvent overnight and try to separate the cover by tapping utility knife blades into the joint. This is, imo, the trickiest part of working on the pump.
Press out impeller shaft.
Press out seals and bearings. I can't recall if the bearing in the main pump body is retained by a large circlip (snap ring).
Remove O rings, clean off old gasket.
Clean up sealing faces on impeller where carbon seals run (a lathe might be very useful here, but all I've ever had was a fine file and abrasive paper). Don't remove too much material, remember that although seals are spring loaded, they can only move inwards so far.
Clean body of water pump and end plate, checking that there is no severe corrosion. Remove drain plug (10mm head?) and clean drain hole. Ensure bypass hose outlet stub (circa 5/16" - 8mm) is clear and not excessively corroded. Check if any 'weep' holes are used and that they are unblocked.
Fit the new O rings, bearings and seals to the casing and cover plate.
Insert impeller shaft into the pump body and press it home.
Fit cover plate and press it home.
Fit fan assembly.
Fit drive pulley.
Note :- the reason I repeatedly use the word PRESS above is because this is the best way. Using a hammer even a soft faced one runs the risk of fracturing one of the water pump seals (they consist of a brass housing with a spring-loaded CARBON ring - carbon is brittle). If you don't have access to a press, you could maybe use a large bench vice, a couple of large C clamps etc.
Tip (or maybe not!). Some Techs back in the day, after rebuilding the water pump, would run the engine for 2 minutes or so before installing the coolant - the thinking was that running the new seals dry initially would help them bed into/seal better against the old impeller sealing faces.
Tip No.2 :- while you have the water pump removed, it's an ideal opportunity to flush the rad, cylinder head and block. The little bypass hoses on the cylinder head between coolant outlet and thermostat housing and also the water pump often get blocked. I suspect these blockages can contribute to possible overheating and subsequent head gasket failure which affected many of these rear engined cars. Don't be surprised to find the little pipe stubs on the head/thermostat housing to be badly corroded and near failure - better to find this out now than out on the road...
Hth,
AL.
I've rebuilt a few of these water pumps many years ago - not difficult to do, just gotta be careful not to break anything...
A quick search shows www.midwest-bayless.com in the U.S. stock a rebuild kit and you can see this includes 2 x seals, 2 x bearings, a couple of large O rings and a gasket.
The rebuild procedure is usually well covered in any decent shop manual, but in case you haven't got one, here's what I can remember.
Basic procedure is :-
Remove waterpump from engine
Remove fan housing, fan and belt drive pulley. Also remove the woodruff keys (shaft keys).
Clean up each shaft end outboard of the bearings, this makes it easier to open up the pump.
Remove end plate (4 x 10mm headed bolts). Be very gentle with this, don't use a hammer and chisel or pry too hard. I'd suggest soaking the gasket in solvent overnight and try to separate the cover by tapping utility knife blades into the joint. This is, imo, the trickiest part of working on the pump.
Press out impeller shaft.
Press out seals and bearings. I can't recall if the bearing in the main pump body is retained by a large circlip (snap ring).
Remove O rings, clean off old gasket.
Clean up sealing faces on impeller where carbon seals run (a lathe might be very useful here, but all I've ever had was a fine file and abrasive paper). Don't remove too much material, remember that although seals are spring loaded, they can only move inwards so far.
Clean body of water pump and end plate, checking that there is no severe corrosion. Remove drain plug (10mm head?) and clean drain hole. Ensure bypass hose outlet stub (circa 5/16" - 8mm) is clear and not excessively corroded. Check if any 'weep' holes are used and that they are unblocked.
Fit the new O rings, bearings and seals to the casing and cover plate.
Insert impeller shaft into the pump body and press it home.
Fit cover plate and press it home.
Fit fan assembly.
Fit drive pulley.
Note :- the reason I repeatedly use the word PRESS above is because this is the best way. Using a hammer even a soft faced one runs the risk of fracturing one of the water pump seals (they consist of a brass housing with a spring-loaded CARBON ring - carbon is brittle). If you don't have access to a press, you could maybe use a large bench vice, a couple of large C clamps etc.
Tip (or maybe not!). Some Techs back in the day, after rebuilding the water pump, would run the engine for 2 minutes or so before installing the coolant - the thinking was that running the new seals dry initially would help them bed into/seal better against the old impeller sealing faces.
Tip No.2 :- while you have the water pump removed, it's an ideal opportunity to flush the rad, cylinder head and block. The little bypass hoses on the cylinder head between coolant outlet and thermostat housing and also the water pump often get blocked. I suspect these blockages can contribute to possible overheating and subsequent head gasket failure which affected many of these rear engined cars. Don't be surprised to find the little pipe stubs on the head/thermostat housing to be badly corroded and near failure - better to find this out now than out on the road...
Hth,
AL.
Last edited:
Would be great to see some pics of your car..and motor
Charlie
Charlie
Thanks for this procedure. I have a question. On pressing out the bearings and seals, do they both press out toward the center of the pump? The seals can only press out inward, but the bearings might be outward. What is your recollection? Thank you.Ex Fiat Dealer Tech in the 70's here.
I've rebuilt a few of these water pumps many years ago - not difficult to do, just gotta be careful not to break anything...
A quick search shows www.midwest-bayless.com in the U.S. stock a rebuild kit and you can see this includes 2 x seals, 2 x bearings, a couple of large O rings and a gasket.
The rebuild procedure is usually well covered in any decent shop manual, but in case you haven't got one, here's what I can remember.
Basic procedure is :-
Remove waterpump from engine
Remove fan housing, fan and belt drive pulley. Also remove the woodruff keys (shaft keys).
Clean up each shaft end outboard of the bearings, this makes it easier to open up the pump.
Remove end plate (4 x 10mm headed bolts). Be very gentle with this, don't use a hammer and chisel or pry too hard. I'd suggest soaking the gasket in solvent overnight and try to separate the cover by tapping utility knife blades into the joint. This is, imo, the trickiest part of working on the pump.
Press out impeller shaft.
Press out seals and bearings. I can't recall if the bearing in the main pump body is retained by a large circlip (snap ring).
Remove O rings, clean off old gasket.
Clean up sealing faces on impeller where carbon seals run (a lathe might be very useful here, but all I've ever had was a fine file and abrasive paper). Don't remove too much material, remember that although seals are spring loaded, they can only move inwards so far.
Clean body of water pump and end plate, checking that there is no severe corrosion. Remove drain plug (10mm head?) and clean drain hole. Ensure bypass hose outlet stub (circa 5/16" - 8mm) is clear and not excessively corroded. Check if any 'weep' holes are used and that they are unblocked.
Fit the new O rings, bearings and seals to the casing and cover plate.
Insert impeller shaft into the pump body and press it home.
Fit cover plate and press it home.
Fit fan assembly.
Fit drive pulley.
Note :- the reason I repeatedly use the word PRESS above is because this is the best way. Using a hammer even a soft faced one runs the risk of fracturing one of the water pump seals (they consist of a brass housing with a spring-loaded CARBON ring - carbon is brittle). If you don't have access to a press, you could maybe use a large bench vice, a couple of large C clamps etc.
Tip (or maybe not!). Some Techs back in the day, after rebuilding the water pump, would run the engine for 2 minutes or so before installing the coolant - the thinking was that running the new seals dry initially would help them bed into/seal better against the old impeller sealing faces.
Tip No.2 :- while you have the water pump removed, it's an ideal opportunity to flush the rad, cylinder head and block. The little bypass hoses on the cylinder head between coolant outlet and thermostat housing and also the water pump often get blocked. I suspect these blockages can contribute to possible overheating and subsequent head gasket failure which affected many of these rear engined cars. Don't be surprised to find the little pipe stubs on the head/thermostat housing to be badly corroded and near failure - better to find this out now than out on the road...
Hth,
AL.