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Electric Water Pumps - Thoughts/Suggestions?

Posted: Wed Jul 23, 2014 8:32 pm
by Zelandeth
Both of my previous rear engined Skodas showed quite an alarming tendency for the engine temperature to skyrocket just after the engine is switched off, especially if you haven't had the opportunity to "cool off" after a faster drive. My current one has proved to be no exception to this. It's something that I would like to do something about, especially given that I now live in the city of 70mph dual carriageways! Generally not a huge problem as I try to be quite gentle with the car for the last ten minutes or so before stopping. However that's not always possible - see also stopping at motorway services for instance.

I'd pondered the installation of an electric water pump many years ago to just keep thing circulating for a five or ten minutes after the engine is turned off.

Has anyone here set up anything like this with their cars before? If so, has anyone got any suggestions as to what sort of pump I should be looking for, and any traps to watch out for? Also, how much should I be expecting to spend?

Not intending really to interfere with the operation of the system as it is during normal running - I just really want to try to kerb the downright alarming heat soak that seems to plague these cars.

Re: Electric Water Pumps - Thoughts/Suggestions?

Posted: Wed Jul 23, 2014 8:44 pm
by Hannesb

I have no personal experience with this, but I do have a question. What happens when the engine stops turning over the mechanical pump? Will that not pretty much block any flow that an electric pump would provide, or could you somehow bypass that altogether? Maybe the impeller wouldn't cause too much of an obstruction - I suppose the coolant only really needs to keep moving through the radiator for a while after you switch the engine off.

I know that modern cars (by which I mean everything that is newer than mine) can run the fan after the engine is switched off, but it never really occurred to me that there may be a pump pushing the coolant around as well. Probably pointless cooling the radiator itself down if the coolant isn't circulating...


Re: Electric Water Pumps - Thoughts/Suggestions?

Posted: Wed Jul 23, 2014 8:47 pm
by excossack
Something like one of these ... 4618534793 on a delay timer so when you kill the ignition it runs on for xx mins?

I can do something like that but as a turbo timer on the car alarm. (not that I do.)

Re: Electric Water Pumps - Thoughts/Suggestions?

Posted: Wed Jul 23, 2014 8:52 pm
by Zelandeth
Yeah, that's the Davies-Craig unit that kept popping up when I was nosing around earlier.

The mechanical pump is a centrifugal type, so won't cause a massive obstruction to flow. Shouldn't need a massive amount of flow for this purpose either, just enough to help dissipate the "decay heat" for want of a better term from the engine.

The cooling fan on the Estelle is always live, so if the water in the radiator is hot enough, it will run. The issue though is that there's ten feet or so of piping between the engine and the radiator, so it really does rely on the pump to cause any circulation. No thermosyphon effect really doing anything here!

Re: Electric Water Pumps - Thoughts/Suggestions?

Posted: Wed Jul 23, 2014 9:07 pm
by Zelandeth
My money is on the route taken from the engine to the radiator - and that both the inlet and outlet are at the bottom of the radiator, so there's no reason for water to rise/fall.

Normal running temperature is 80C, but it will spike up to 95C give or take whenever you stop the engine. 100-105C (gauge maxes out at 120) if you've done something like pulling off the motorway to get fuel without a gentle cruise for 10 mins or so beforehand.

Fact that there's no damping on the temp gauge so it pings up to whatever it's sitting at instantly when you turn the ignition on means that this is probably more noticeable than it might be on some other cars.

Re: Electric Water Pumps - Thoughts/Suggestions?

Posted: Wed Jul 23, 2014 9:15 pm
by Zelandeth
One does wonder if this is actually one of the reasons that these cars have such a reputation for cylinder head gasket failures. Being an alloy block with a cast iron cylinder head you're always going to get differential expansion rates causing thermal stresses - but having the temperature spike every time you stop the engine really can't help!

Re: Electric Water Pumps - Thoughts/Suggestions?

Posted: Wed Jul 23, 2014 9:48 pm
by Zelandeth
Valid point I guess!

Point remains though that I need to try to do something to try to get rid of the heat that is there...Just need to decide how to go about it.

At least the simplicity of the system means that it shouldn't be too difficult to plumb something in.

Re: Electric Water Pumps - Thoughts/Suggestions?

Posted: Thu Jul 24, 2014 12:30 pm
by Hannesb
Would something like this hooked up to a temp sensor and a small pump work? ... 1423.l2649