Help with multimeter settings to manually bleed coolant

First double-take: why is there a video saying you need a multimeter to bleed coolant?

Ok, the video shows using a multimeter as a jumper wire across the CHRS pump relay socket, as a way to get that pump to run without using a scan tool.

If you don't care about seeing an amps reading while the pump runs, you can do the same thing with a humble jumper wire.

 

I thought Gen2 Prius engine water pump is belt driven?

 

Gen 2 Prius has three engine water pumps: the belt-driven one, the electric one that shifts hot coolant in and out of the thermos on shutdown and startup (the "CHRS pump"), and the electric one that circulates coolant through the heater when the engine is off.

(Of course, none of those three should be confused with the other electric one that's for inverter cooling, and not any part of the engine cooling system.)

The video shows jumping across the relay socket to run the CHRS pump, in case you think there could be air in the thermos and its part of the flow path.

If you stuck a humble jumper wire between the same two relay terminal sockets where this guy puts the meter probes, the pump will run, and will draw the same amount of current it would with your multimeter. The multimeter is a current measuring device, not a current limiting device.

(The multimeter does, though, have a limit to the current it will withstand, which is why you'd have to be sure the probes are in the higher-range sockets on the meter. Exceeding the limit will blow a replaceable internal fuse in a good multimeter, or do something else in a cheap multimeter.)

Toyota folks can say creative things sometimes. The car already has a fuse for the circuit that you are completing with a wire there.

I wasn't around to see the sparks that concerned you, but having a fuse in the wire doesn't make sparks not happen. If the pump draws too much current, a fuse will (eventually) blow, but it isn't a current regulating device.

An electric pump is an inductive load that's likely to show you some nice sparks when you complete and open its circuit. That's just the way of things. Making the connection quickly and surely (rather than bouncing the wire ends around) minimizes the light show. Multimeter probes might have a better shape for making a quick sure connection there, compared to the ends of some random wire.

If so, you could also use two multimeter probe leads connected together, without a multimeter.

 

The only difference between a multimeter set for amps stuck between those socket terminals, and a plain wire between the same two terminals, is that the multimeter will show you how much current is going through it, and the wire won't. Everything else that happens will be the same.

The way you say "the pump" makes me wonder if you're forgetting that the car has three pumps for the engine cooling system. (See post #7.)

The only pump that guy is running with the multimeter is the one for the coolant heat storage tank (thermos).

The belt-driven pump only runs when the engine does. No way around that.

The one for the heater will run if the car is IG-ON, the heater is calling for heat, the engine is stopped, and the coolant is hot. But then again, getting the coolant hot usually involves running the engine.

 

That relay socket is jumped using the ammeter setting on a multimeter. Ammeter means that it reads current. (Why not Amp Meter? Apparently because it sounded odd to people back in the day.)

Ammeters can get a little tricky because most multimeters have sockets which must be used for particular ranges, and there is usually fine print concerning usage only found in the manual. The ammeter works by putting current through a device called a shunt, which is just a resistor with very low resistance, then it measures the voltage across the shunt. V/R=I, R is set by which mode/shunt is selected, V it measures, which gives I, the current. The multimeter on the right has a range "A" (no specified value) and 30A (30 amps). The manual for the Innova indicates that it has 3 ranges:

https://csr.innova.com/Content/Manual/Innova/030412_3340A_93-0067_RevB_English_Final_downloadable.pdf

(page 6)

but you can rule out the first two because they are 40 and 400 mA, and the pump will likely exceed that. The 15A socket has a note that it shouldn't be used for more than 15 seconds continuously, and it should rest 15 MINUTES between tests. It also states that the 15A socket is NOT fused and the lower ones are. So using it in those modes would likely blow the fuse inside the multimeter. They can be replaced, but sometimes it is a royal PITA to do so. Aiman's video says to run the pump for not more than 30 seconds - 15 seconds longer than the Innova says is acceptable. In this particular situation I would suggest using that multimeter for 10 seconds in the 15A mode (one lead in the 15A hole, the other in Com(mon) hole, dial turned to 15A) to be sure the current drawn is sane - in this case less than 15A. Then just use a piece of wire to jump the relay for 30s at a time. The only danger would be if the pump shorted out completely during the bleed, which is unlikely. Well, the other danger would be sticking the probes/wire in the wrong socket holes - don't do that, it will almost certainly blow a fuse in the car.

For whatever its worth, I did this once using a free Harbor Freight multimeter with a 10A range and only rested it a minute or so between 30s bursts, and it survived. (HF has since raised the price on similar multimeters to $4 and downgraded them to 5A DC.)

 

Yes, but read the limitations on that node in my post right before this one.

 

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That's because that pump doesn't kick on in maintenance mode or heater on or what have you. It only comes on for a few seconds, once, before cold-starting the engine if there's hot coolant in the thermos, and again, once, for a few seconds, when you shut the car off, to save hot coolant in the thermos.

Yes. (Again, the meter isn't doing anything for you there that a simple wire wouldn't, but if you insist on using a meter, the way you've set that up will work.)

They probably calculated the time limit for a current that is near the 15A maximum. You can probably get away with 3 or 4 amps for longer than that (though the meter vendor might show little sympathy if you don't).

The factory original radiator has a bleed nipple on its upper left side. That's left side of the car, left when you're facing the same way the car is. If the guy said right, he probably meant your right if you're standing in front of the car looking back at it. But that's not the normal way to use 'left' and 'right' around cars.

The bleed nipple on the factory radiator has a hex-socket-head bleed valve that's on the top of that corner of the radiator. You can see the guy in the video using a long Allen wrench down through the thoughtfully-provided hole in the core support sheet metal for access to the bleed valve.

Some aftermarket replacement radiators don't have the bleed nipple or valve at all. I spent like 20 minutes questioning my sanity once when I couldn't find it. Anyway, it turns out even when the radiator lacks that, you still can manage to get the cooling system filled.

 

As has been mentioned a couple times, using the meter for that doesn't accomplish anything different from using a simple wire the same way. The wire doesn't have any settings you have to think about. If you're concerned about how to set the meter, or possibly damaging the meter, the easiest answer is don't use the meter.

 

I thought there was a bleed valve on heat storage pump thermos? Wouldn't that be better to use?