Remote Electric Water Pump

[gongloo]

It looks like you have several bad circuits to me, E.G., the radiator's inlet and outlet are virtually connected to the same place, the thermostat outlet(s).

Agreed it's not clear from the diagram, but the intention is that a bypass thermostat is used, with flow going exclusively up to the radiator feed when hot, and flow going exclusively direct to the pump bypassing the radiator when cold. I'll see if I can update the diagram at some point to reflect this.

The otterstat should be immediately downstream and close to the thermostat.
Actually, it's in a bad place already. Ideally, it should be in one of the heads (replacing it with a sensor, as previously suggested).

That's an interesting thought. I'm not sure I understand why placing it in one of the heads would be better. Admittedly I'm no expert in cooling systems, so I have a lot to learn here. Can you elaborate, perhaps with example scenarios and expected behaviors?

I'm sure you already know this but higher amp alternators won't fix how they wired up the car, the size of the wires they chose to use and corroded/dirty connections, etc.

Absolutely. Separately on my list of "someday" projects, I'd love to completely gut the car's wiring and build completely new harnesses throughout. Seems like an awful lot of pain but it would give me peace of mind around longevity of the electrical system. I haven't made time yet to do the whole system, but for certain isolated systems I have gone through the trouble to rebuild the wiring for from scratch (some of the lighting circuits, for example). It's especially tedious to do while matching wire colors and plugs, but in my experience totally worth it and (perhaps masochistically) very satisfying.

[Dangermouse]

FWIW, my only experience with an electric water pump have been on the BMW N52 engine; I'm sure others are available on the market but I will offer the following experiences of that particular unit (other units may have different strengths and weaknesses YMMV, etc):

1. When it fails, there is no warning (no weep hole etc) unless you routinely run BMW software to check it's health, which brings me to
2. It is BUS operated only. No straight 12VDC. No idea if you can get a 12VDC On/Off automotive electric water pomp
3. The BMW one is variable speed according to engine revs, which keeps engine at most efficient cooling and supposedly is good for 0.0001 mpg gain
4. When it fails, the BMW ecu is smart enough to put the engine in limp mode and protect it from overheating. But you are suddenly stuck at the side of the road. The Delorean's isn't and you will be.
5. It is surprisingly heavy, possibly heavier than a comparable mechanical one, as all the electronics are integral to it
6. Keep it at the lowest point in the circuit as the rotor and bearings are cooled and lubricated by the coolant fluid
7. It cost $400.

[David T]

The "O" switch (Otterstadt) is supposed to be in the coolant flow far enough away from the motor so radiated heat won't affect it. Once the thermostat opens and the hot coolant flows over the switch, it senses how hot the coolant is and if hot enough, turns on the fans. Most cars have the switch threaded into the inlet tank of the radiator. The wiring of the whole car could stand a LOT of improvement. From increasing the gauge of the wire to better plugs and connectors, improved fuseblock, maybe break it into two, one in front and one in back, a separate grounding system, a V+ bus and a V- bus, more relays, all kinds of things. There is just so much you can do to an old car that was designed and built long ago.

[gongloo]

The "O" switch (Otterstadt) is supposed to be in the coolant flow far enough away from the motor so radiated heat won't affect it. Once the thermostat opens and the hot coolant flows over the switch, it senses how hot the coolant is and if hot enough, turns on the fans. Most cars have the switch threaded into the inlet tank of the radiator.

I've been thinking about why the otterstat should be on the inlet side of the radiator rather than the outlet side (disregarding the change in otterstat trigger temperature that would need to be accounted for), and realized that likely it's better to actually have it on the inlet side in all cases; really what we want to control for here is a maximum temperature of coolant leaving the engine, without regard for the temperature of coolant entering the engine. In practice, given a correctly tuned system, I suspect it's likely to not make all that much difference anyway.

[Ron]

That's an interesting thought. I'm not sure I understand why placing it in one of the heads would be better. Admittedly I'm no expert in cooling systems, so I have a lot to learn here. Can you elaborate, perhaps with example scenarios and expected behaviors?

WRT coolant problems, the cylinder heads are much more prone to heat damage than any of the other parts. The best way to prevent damage is for the coolant system to react to high head temperatures as soon as possible. This is the main reason the automakers moved many of their sensors (fan and gauge/light) from the thermostat housing and coolant ports in their intake manifolds to the heads. (DeLoreans will do this if you simply rotate the pipe the otterstat resides in 180°!) Another is, if the thermostat sticks, the coolant will not flow over the sensor and the heads will fry before the gauge/light indicates a problem or the fans come on. Same result if there is air surrounding the thermostat. We want to know how hot the head is without relying on things that can fail and prevent the sensors from doing their job properly -- A single device, as close to the place where a problem is most likely to occur, is the best solution.

Briefly on the flow at the thermostat- When the engine is cold, you don't want a lot of the coolant going through the engine. The thermostat's job is to make the engine warm up quickly so that the oil (and O2 sensors on some vehicles) performs properly.

[Ron]

The "O" switch (Otterstadt) is supposed to be in the coolant flow far enough away from the motor so radiated heat won't affect it.

?? On a DeLorean, you couldn't get it much closer to the exhaust manifold, the hottest thing under the hood.

Most cars have the switch threaded into the inlet tank of the radiator.

?? Most cars have no switches threaded into the radiator tank, although some have coolant level sensors.

[Ron]

I've been thinking about why the otterstat should be on the inlet side of the radiator rather than the outlet side (disregarding the change in otterstat trigger temperature that would need to be accounted for), and realized that likely it's better to actually have it on the inlet side in all cases; really what we want to control for here is a maximum temperature of coolant leaving the engine, without regard for the temperature of coolant entering the engine. In practice, given a correctly tuned system, I suspect it's likely to not make all that much difference anyway.

YES!!!
...except it does make a difference...

[Bitsyncmaster]

I've been thinking about why the otterstat should be on the inlet side of the radiator rather than the outlet side (disregarding the change in otterstat trigger temperature that would need to be accounted for), and realized that likely it's better to actually have it on the inlet side in all cases; really what we want to control for here is a maximum temperature of coolant leaving the engine, without regard for the temperature of coolant entering the engine. In practice, given a correctly tuned system, I suspect it's likely to not make all that much difference anyway.

I thought about the same thing when I was designing my electronic otterstat. My thought was maybe you could reduce the fan run times a little but I never really saw that it would save anything.

[David T]

The "O" switch is only supposed to turn the fans on and off. It doesn't care how hot or cold the coolant is, it only controls the fans. The temperature sender for the gauge IS in the head where most of the heat originates from. The problem with that though is, if the coolant level gets too low and the sender is no longer immersed in coolant, it won't tell you how hot it really is! I never said the "O" switch is in the ideal spot in a Delorean, I said where it should be. I agree it is close to the exhaust but it doesn't really seem to have that bad an effect on it. A lot of cars, especially imports, have the fan switch in the radiator tank. On newer cars the computer keeps tabs on the performance of the water pump and the fans and if it senses performance outside of the accepted range it throws an error code and lights the check engine light. It will also modify the engine parameters to try to reduce the heat generated to "limp home" mode. Deloreans can't do that but the driver can. For instance, if you see the temps are going up you *can* turn on the heater to try to help cool the coolant.

[DMCMW Dave]

The "O" switch is only supposed to turn the fans on and off. It doesn't care how hot or cold the coolant is, it only controls the fans.

Huh?