Has anyone replaced their engine-driven water pump with an electric?

Just thinking that running the fans after shutdown is likely a waste of time since none of the coolant is being circulated into the engine. An electric would take care of this issue.

What are the difficulities in replacing the engine pump with an electric?

What about adding an electric as a supplemental pump that would run for some preset time period along with the electric fans (I've ditched my engine driven fan) to cool off the block?

Thanks,
John
1987 XJ-S, V12, 62000 miles

 

you'd have to run one inline instead of replacing it. but look on.the internet there is a guy with a modded xjsc with twin electric water pumps

 

i like the davis-craig pump and system, just about the best cooling idea yet!

plenty of flow at idle,when engine pump slows down.

adequete at top speed.

but the best is after hot shutdown, water pump and elec. fan cycle on and off,till a pre set temp is reached, gotta be the best way!
and it saves overall weight, like 15lbs. or more.

i like it!!

 

What would you expect to gain by recirculating the coolant after shut down? Does your car suffer from vapour lock or perculation?

 

mikey , check out Jag v12 engines XJS and XJ12,, the dreaded dropped valve seat has blown up many of them, simply because after shutdown heat rises, soaks up into the heads, expands the aluminum and the steel seat loosens up and drops down, mostly on later 5.3 HE types, and some 6.L.

pre -HE not so often?

so a good after-cooling system is important, also i think factory use to high thermostats, engines that run cool have less problems with heat.

 

YOW! That's frightening. Thanks.

 

How about someone post a site for the twin electric water pump, I would install the twin if I knew where to purchase and how to install.

Thank you.

 

The installation is VERY tricky as there is so little room for the pumps. The original water pump has to be blanked off, the cross pipe disabled or blocked off at the thermostat housing and the thermostats removed.

All this can be done, but it is a major engineering and fitting job, for what for the normal motorist? You are replacing a robust, basically mechanical system, by a electronically controlled one, with a great many not very robust electronic components and placing these in a very harsh environment. The first you will know that something has stopped working is when the car massively overheats.

Finally, Mr Norman Lutz, of the "Lutz mod" fame has stated that the system in the V12 needs the thermostats and the slight back pressure they cause, for the cooling system to function correctly. I have no idea if that is true or not, but the guy knows a great deal about our cars.

A decent radiator and the stack kept free of rubbish, a really good main electric and modern auxiliary fan installed, and a post-shutdown timer relay in the main fan circuit so the main fan keeps running for (say) 5 minutes if it is on at ignition switch off, and the engine will function as intended. And if you are really worried, pop the bonnet (hood) for half an hour after a hot stop.

Just my beliefs, mind.

 

The real benefit as I see it, and applying it to my particular case, is that my one great fear is dropping a valve seat. I don't know that I could ever justify the expense of getting that fixed in a car this old (and with my limited financial resources). So I may just deal with however tough the installation may be.

I wouldn't think it would all that difficult to create a bit of back pressure if it's needed, either by inserts or by disabling the thermostats in the open position so the system "sees" them as there and open.

I'm putting four thermisters on the engine, one in each coolant manifold, and will monitor them with a fairly simple/cheap/easy LED system, thus I'll be aware of coolant temps in realtime.

I guess I'm still missing the advantages of running the fan(s) after shutdown, I can't imagine they would help to quickly cool the engine, but I could be wrong about that.

As far a opening the bonnett, I do it every time I'm at home, but doing so somewhere where I don't have close control of the car would make me a bid nervous.

I wish I could get ahold of a pump to see how difficult it would be to fit. Need to give it more thought.

Thanks,

John
1987 XJS V12, 62,000 miles.

 

Is this right? after parking aux fan comes on to cool engine with air only as there is no coolant circulating thru the motor without the water pump turning. If this is the case seems like an electric pump would be good.

 

Greg In France sums it up rather well and matches my own experience exactly.

a properly set up and CLEAN radiator with a functioning water pump as per factory specification is the correct way to cool the V12. Any changes that play around with these basic principles simply either creates a problem or moves it elsewhere in the engine. Attention to detail and proper maintenance are the basis for a fully functional cooling system.

How do I know; again simple, serious overheating before as a result of a PO not paying attention to the basics (clean radiator & no crap between the cores) had a professional clean-up and now use the 1984 HE as a daily commute in heavy traffic without any temperature problems whatsoever and, yes, in Australian 35c temperatures.

having done real research on the subject of "dropped valve seats" it is evident that this might be a rather interesting "urban myth" rather than a real problem. Perhaps we need to undertake a substantiated poll among our members to see what percentage had "dropped valve seat" problems and under what circumstances.

have a great day
BernardS

 

good idea, start the poll.

 

Those are good comments. Believe me, I don't look forward to messing with the cooling system any more that I already have...which is just ditching the engine fan and putting in an electric. The radiator is re-cored, new coolant fill tank, new hoses, cleaned out all the pipes and coolant manifolds, replacing all the seals and gaskets.

I would be interested in knowing the frequency of dropped seats, and the average cost of repairs.

I'm off to work, but if I can sort out how to start a poll later today I'll do so.

Thanks,

John
1987 XJ-S V12, 62,000 miles

 

I was googling electric water pumps on a Jaguar V12 when I came across this thread. I don't know if the poll on dropped valve seats was ever done, but I have had two in my years of ownership. Well, actually one. My XKE cracked a valve seat, but my XJS dropped one. Neither car in my ownership ever remotely ran hot, and my XJS dropped a valve seat sitting in the driveway. I had driven it one morning, to a car club meet, drove home, went to go to a cruise in 3 hours later, and heard it the second I started the car. Sickening. I am not a engineer, but seems to me a pump, and a fan, circulating coolant through the engine, while cooling it, can't be a bad thing? Also, I have been reading on electric pumps. Seems several manufacturers are at least putting electric booster pumps on from new. Electric power steering is common for sure. Maybe we haven't seen electric pumps installed from the factory, is because of cost???

 

v12s.com has an electric water pump kit for our cars I think. Seems like a good idea; having the electric fans and a pump running for maybe 5 minutes after shutdown, but like others in this thread, the added paranoia of having a primary electric pump and it failing outweighs the benefits in my mind.

I had an '89 with a dropped valve seat as a parts car years ago. Not a sound I ever wish to hear coming from on of my V12's ever again..

 

How did you determine they didn't run hot? The gauge that may or may not have indicated properly? Nothing should just be dropping seats for absolutely no reason. I know these cars have a reputation for that being one of the only issues, but I have overheated the holy hell out of my V12 and it didn't do anything. And I mean I blew a hose completely and drove it until the valvetrain was LOUD because the oil was so thin. The V12 is a friggin beast.

You are pretty much right about it being a cost thing, they are superior in that they are more controllable, take up less space, and take up less power. You are beginning to see them just as you are beginning to see power steering units change to electrics, just as you have seen electric fans become the mainstay in the past ten years. They allow for a more compact, lightweight design of the engine as a whole, add flexibility and require less power. It is all about the money.

I don't see any point any doing this on the XJS. the water pump lasts 80-100k miles and costs a measly 60 bucks. The amount of power you save is not really of much important for a daily driver and there aren't any cooling gains.

I find a good number of people looking for weird ways to modify their car in search of power or reliability, but i believe that if you just follow the jaguar blueprint and return it to that state, the car will be relatively trouble free. I put in a water pump 2 years ago and I don't plan on worrying about it for a very long time, so what is there to gain from an electric one?

 

Since most valve seats are dropped due to heat soak after the engine has been shut down, the advantage of the electric water pump is that it can be configured to continue running after the engine has been shut off, cooling the engine and preventing heat soak.

Mark

 

I would argue that most dropped valve seats are from being at speed with a neglected or malfunctioning cooling system.

The documented 20 degree increase 30 minutes after shutdown is not going to drop a valve seat

 

I would love to agree, but my latest car dropped a valve seat during the cool down, sitting in the driveway. Heard it as soon as I started it. My XKE on the other hand, had a cracked valve seat. My machinest said I was just lucky it didn't come completely out. I had turned the engine to about 7K, and when I let off, came to the next stop, I heard the excessive valve clearance noise. Didn't know what or why. One listen by my trusted older Jag mechanic, and he didn't want me to even drive it 5 miles home. My XKE never had any signs of running hot. Neither has this XJS. Yet, I bought it as a non running project off of eBay, from a shop that had given up on it, so I have no idea of its history.

 

I've wondered about the dynamics behind this too. For the seat to drop out, there has to be a temperature differential between it and the head. It's hard to imagine that the valve seat cools faster than the head causing it to shrink, but I can't imagine the head getting hotter after shutdown than when it was runing.

The soakback effect seen on the temp gauge is the coolant absorbing the residual heat of the engine.

Anybody here understand the full story?