Orange4boy's Rescue and Revival of a 2003 Prius

[orange4boy]

Almost forgot...

Invisible lower grille block finished. I just snapped out the stock screen, cut some black coroplast and screwed them together. Snapped the screen back in. Done. Just have to move the OAT gauge into the tow ring opening.

Engine blanket started... Just have to work out hood clearance issues. Photos soon.

Next... Partial belly pan. See:Autospeed: modifying undercar airflow. Classic article about the Classic Prius. One of many very good articles. Actually these are about the NHW10, mine is an NHW11 but the body is the same.

[bwilson4web]

Originally Posted by orange4boy

So the heater core and engine block share a circuit and the rad is separated from that by the tstat. I forgot about that. So the inline coolant heater can circulate (by convection) the coolant thru the block with the tstat closed. Potentially much better pre heat than a block heater especially for the cabin air.

Could there be a sweet hack here using the existing inline coolant pump and a passive inline heater to really warm the engine/heater core loop? This would be much better/cheaper than relying on the convection of the tank pump's bypass system.

I'm feeling warmer already...

Thoughts?

It would take the pump because the inlet and outlets are on top:


The plumbing is not trivial but doable.

Bob Wilson

[bwilson4web]

Originally Posted by orange4boy

. . .
Invisible lower grille block finished. I just snapped out the stock screen, cut some black coroplast and screwed them together. Snapped the screen back in.

Did you go in from the bottom?

Originally Posted by orange4boy

. . .
Next... Partial belly pan. See:Autospeed: modifying undercar airflow. Classic article about the Classic Prius. One of many very good articles. Actually these are about the NHW10, mine is an NHW11 but the body is the same.

I'm interested in the pattern if you can take a photo including a ruler or outer dimensions before final fitting.

Bob Wilson

[orange4boy]

An inline passive heater only requires 1" cut out of a hose in the right location and two hose clamps. Turn on the pump and plug in the heater and you have full block and core pre heat.

I wish there was a circulation diagram on the heater circuit. Is there anything in the official manual?

[orange4boy]

Did you go in from the bottom?

Yes. I had the car on jacks for the aborted block heater install. The plastic covers are held on by just a few screws. I had not put them all back in anticipation of more work underneath. It's fairly easy to pop off the screen from there.

I'm interested in the pattern if you can take a photo including a ruler or outer dimensions before final fitting.

Will do.

I also adjusted the headlights tonight. not too big a deal.

The coolant tank (pops upward off the metal bracket) and intake snorkel (body clip) have to come off the left side to get at the 8mm nut.

The windshield washer fluid fill tube has to come off the right side (one clip). It's a tight fit on the right side but taking out the washer fluid tank is too much work.

[bwilson4web]

Originally Posted by orange4boy

An inline passive heater only requires 1" cut out of a hose in the right location and two hose clamps. Turn on the pump and plug in the heater and you have full block and core pre heat.

I wish there was a circulation diagram on the heater circuit. Is there anything in the official manual?

The closest I found were various sketches and drawings in the maintenance manuals on how to repair various parts. Nothing like a proper coolant flow diagram. However, I've not seen the "New Car Features" that sometimes has more illustrative sketches.

Bob Wilson

[Christ]

Originally Posted by bwilson4web

The closest I found were various sketches and drawings in the maintenance manuals on how to repair various parts. Nothing like a proper coolant flow diagram. However, I've not seen the "New Car Features" that sometimes has more illustrative sketches.

Bob Wilson

Usually, the one closest to the water pump is inlet.

If you leave the heater circuit closed, one hose might get warm, while the other should stay cold or get mildly warm, as long as the heater valve is in line with one of the hoses.

If the coolant bottle has a heater in it, chances are, it's the lowest point in the system as well, no? Flow probably starts there and works upward into the heater core. Thermosiphon only needs a low spot to start and end, the rest of the system can be level, as long as it can take the pressure build up, the flow still occurs.

[orange4boy]

So the upshot is: place a passive heater at a low point with a straight shot to the inlet of the engine block. The outlet has the tstat. Right?

In this case, there is a coolant pump for the heater core that pumps coolant through the block when the engine is off, which happens a lot in the Prius. This gives me the option of running that pump and a passive cooler to force-circulate the warm coolant prior to engine start. The best place for the passive heater would be the return hose from the heater core as close to the engine as practical. Insulating the hoses would help too I suppose.

The last question I have to answer: Is there a coolant flow valve for the heater core? If so I will have to hack that too.

Luckily, I have one hint as to the direction of flow...

[orange4boy]

Ah ha!







Let the deciphering begin...

First thing I noticed was the throttle body warmer. Another advantage to this idea.

p.s. This was found in the new car features section (under lubrication), just like you thought, Bob.

[bwilson4web]

I wonder if the pipe that connects at the water pump could be cut and a hose go to the heater, located at a lower position. Then the heated coolant would flow up to the cabin heater core and eventually, displace cold coolant into the heater. Mounting the heater will be an interesting challenge.

Another solution might be a resistive, heater wrapped and insulated around the lateral run of this pipe. This would avoid extra tubing and finding a place for the heater tank.

Bob Wilson