Water pump question

[Staggard]

Hi, Question?? Is the water pump gear and shaft cast as one, The only reason I ask is because it seemed to me a good idear that if the driven gear was seperate and secured with a shere pin (like the dizzy) so if the pump sized it would not wreak the engine,jackshaft jamming,chains snapping, valves dancing on top of the pistons,ect you could have a thin split pin under the gear so when you removed the pump the gear did'nt drop in to the engine. What do you think?

[flying farmer]

The problem is not the pump seizing, it is the side loads imparted to the jackshaft by the worn gears, which are sufficient to break down the oil film and seize the jackshaft front bearing. Just before my jackshaft seized I noted the oil pressure had dropped from 45 to 35 psi (this was at a steady 4000rpm on the motorway). Engine temp was fine, the pressure drop probably reflected the amount of heat being put into the oil. Both the jackshaft and bearing area of the block had turned blue with the heat before welding themselves together, and a BIG hammer was needed to seperate them. The water pump still turned fine, despite the tooth damage. This is why I have a belt drive pump on one car, an electric pump on another, and only one with the original (leaky) pump, but it has got a huge mileage on it and the teeth are still perfect
Neil

[Staggard]

The problem is not the pump seizing, it is the side loads imparted to the jackshaft by the worn gears, which are sufficient to break down the oil film and seize the jackshaft front bearing. Just before my jackshaft seized I noted the oil pressure had dropped from 45 to 35 psi (this was at a steady 4000rpm on the motorway). Engine temp was fine, the pressure drop probably reflected the amount of heat being put into the oil. Both the jackshaft and bearing area of the block had turned blue with the heat before welding themselves together, and a BIG hammer was needed to seperate them. The water pump still turned fine, despite the tooth damage. This is why I have a belt drive pump on one car, an electric pump on another, and only one with the original (leaky) pump, but it has got a huge mileage on it and the teeth are still perfect
Neil

Hi Neil where did you get your electric pump from do you have any pics and price Thank's Graham

[V Mad]

In which case we need a weak point at the front end of the jackshaft so that chain drive is not interrupted.

[Staggard]

In which case we need a weak point at the front end of the jackshaft so that chain drive is not interrupted.

so can't we come up with an idear that when the jackshaft seizes the dowel pin shears and the chainwheel continues to turn thus keeping the valves and pistons in sinc

[flying farmer]

My electric pump was a Davies Craig item purchased many years ago to replace the wrecked pump and jackshaft teeth on a Dolomite Sprint engine (uses the same pump) several years ago. It is currently installed on my Stag engined TR as there is not enough room for a belt driven pump, well not Stagdads pump anyway. I couldn't be bothered to make up my own setup as I had the electric pump spare

[flying farmer]

so can't we come up with an idear that when the jackshaft seizes the dowel pin shears and the chainwheel continues to turn thus keeping the valves and pistons in sinc

I think someone on here was fortunate enough to have this happen recently, and the damage to the engine block was minimal as a result.Would probably be difficult to engineer though, and I would rather not have it seize in the first place

[Staggard]

I think someone on here was fortunate enough to have this happen recently, and the damage to the engine block was minimal as a result.Would probably be difficult to engineer though, and I would rather not have it seize in the first place

Sorry to be a bit thick here Niel but I hav'nt had this experience ( yet ) so trying to think ahead. So the problem with the jackshaft seizing is solely due to the water pump so if we do away with the pump the jackshaft does not present a problem on it's own ?

[flying farmer]

The only non water pump related jackshaft problems I have heard of or encountered has been wear of the distributor drive gear and this seems related to high oil pressure, ie over 60psi hot. This is not a problem with the original pump, but can be with the SAAB pump, or with the new County pumps that come fitted with the wrong spring. The original oil pressure seems to have been 45-50 psi
A further problem I have seen is that jackshafts that have had a problem water pump can sometimes wear the front bearing in the cylinder block. Even when the jackshaft has been replaced, the extra clearance on the jackshaft bearing can drop oil pressure as it is fed off the main oil gallery. This means the block has to be bored and sleeved which is another expense

[Sheepdip]

[QUOTE=flying farmer;157429]The problem is not the pump seizing, it is the side loads imparted to the jackshaft by the worn gears, which are sufficient to break down the oil film and seize the jackshaft front bearing. Just before my jackshaft seized I noted the oil pressure had dropped from 45 to 35 psi (this was at a steady 4000rpm on the motorway). Engine temp was fine, the pressure drop probably reflected the amount of heat being put into the oil.

Sorry Neil but don't share your views. I think its the other way around, the jackshaft front bearing starts to seize, burns the oil away and prevents splash getting to the pump gears which are then damaged. When mine happened (after 1500 miles all new bits) was a healthy 50psi. Why the jackshaft seizes is still the question, my feeling its something to do with the timing chain setup, maybe overtight and excessive sideload? Recall EJWard convesation, most of the time they'd come across it was after front end engine work.

Like the idea of a shear pin on jackshaft, it already has one on the gear wheel but guess its just too strong..... The only other thought is loss of oil pressure when it stops, but guess the disi will stop it anyway.

Paul

[Staggard]

So for the engineers out there would it not be possible to machine the block to replace the front jackshaft bearing with a ball/roller bearing or would that be too costly, but if we live in fear of the jackshaft sizeing (and all that's involves) what's the price of peace of mind. What I was trying to get to the bottom of is how many jackshaft's have sized that allready have water pump mod's Graham

[Sheepdip]

Well its a nice idea but not as simple as it sounds - the journal is directly fed from the main oil gallery so acts like a main bearing and has to share supply with them, a ball race would let all the oil happily squirt out. Also there are lots of engines out there happily running OE hundreds of thousands of miles on, that can't all be down to luck. Still suspect front end. I now have a rejournalled block and external pump and much slacker chains as I now know I used to overtighten, oil pressure not as high as I'd like which I suspect is slack in the journall, but still running after 4k.

[Ian Durrant]

The blocks I have seen that have been re-sleeved appear to have been re-sleeved with phosphor bronze. Would that not prevent seizing anyway?

[Sheepdip]

I guess it could only help as its a softer materiel and probably should have been there in the first place, that said plenty of originals happily whirring away so I'm not convinced we've found the answer. As a hapless victim I'd love to know the reason why. The 12vane seemed more problematic, I found out by accident the block casting inside around the pump markedly differs on my 2 engines, one definitely a Mk2 with 12v (that failed), the other not sure. Maybe something there....

Paul