7M Coolant flow

[adampecush]

and a bunch of these responses are exactly why I don't stop by often.

the yellow highlighted line is the heater bypass. When coolant flow is blocked or reduced to the heater, coolant flows out of the motor, through the highlighted line, to the water outlet. When coolant is routed to the heater, it partially flows through the heater return line, back to the water pump (as the heater has now done the job of the radiator on this coolant stream)

 

[CyFi6]

That kind of makes sense, but what causes more pressure at the back of the head than the front of the head when the heater is off? And if this is the case why does it need a bypass why can't the coolant just flow through the coolant passages in the head to the front of the head?

 

[jdmfreak]

Wouldn't it be the same pressure that flows coolent through the heater core

 

[CyFi6]

Wouldn't it be the same pressure that flows coolent through the heater core

No, because the heater has water pump "suction" on the other end whereas this pipe thing doesn't.

 

[jetjock]

That kind of makes sense, but what causes more pressure at the back of the head than the front of the head when the heater is off? And if this is the case why does it need a bypass why can't the coolant just flow through the coolant passages in the head to the front of the head?

The problem is definitely too much head pressure alright. Reminds me of the film Scanners :icon_razz

 

[Grandavi]

The cooling system is a closed system. There is no such thing as suction.., only positive or negative pressure.
Bypasses serve a logical function.

What's the concern?

After reading the following 4 posts.. lol.. I will clarify...

The water pump is meant to flow the coolant in one direction. The Toyota engineers (in between beers) decided to put the hoses the way they are for good reasons. Then they decided to put them in areas that normal people can't reach.. and then opened another beer and chuckled...

My questions was.. what are you trying to figure out? Are you verifying that the hoses are needed? Because you can bypass the heater core altogether.. just wondering what the concern is?

 

[jetjock]

Probably why he put "suction" in quotes. Pumps work by reducing pressure at the inlet.

 

[3p141592654]

Suction is a very common term used in the A/C world when referring to the input side of the compressor..

 

[Bmettie]

I think it's only purpose is when the t-stat is open, water is pumped into the block up into the head then out the front of the head at the t-stat housing and through that pipe to the t-stat housing, this way the back of the head gets circulation. If not without the heater core flowing, the back of the head would never get any circulation.

 

[CyFi6]

Bump can anyone else elaborate on this? Is its purpose to "split" the coolant volume to the radiator by having half of it come from the front of the head and half of it come from the rear of the head? Why does it need to do this?

 

[adampecush]

??

you don't want coolant flowing into one side of the head and out the other. temperature gradients are bad things. 2 outlets means more even coolant temperatures. Here's a general summary of where the lines flow.

heater bypass at back of head -> water outlet behind thermostat
coolant port at front of head -> water outlet behind thermostat
line to heater -> heater
line from heater -> suction side of water pump (because this has alread passed through a "radiator", it is considered cold)
discharge side of water pump -> block/head internal passages
radiator outlet -> water pump suction
front of thermostat ->radiator inlet (top)

I don't think it can be simplified any more than this.

 

[CyFi6]

OK I guess I can live with that explanation lol thanks adam. One thing still has me curious though, if there are two outlets on the head why aren't there two inlets for water in the block rather than just one large opening for water to enter the block on the front only?
You said you don't want coolant flowing in one side and out the other, but it doesn't do that, it flows into the block from the front, then up into the head from the bottom, then apparently out of the head on either side.

 

[adampecush]

1 - The coolant entering the block is a uniform temperature and flows unrestricted into the block
2 - The majority of heat absorbed by the coolant is in the head

 

[CyFi6]

Makes sense, thanks.

 

[jetjock]

It's finally over. Thank God

 

[CyFi6]

So when bypassing the heater core it would actually be better to plug the ports rather than loop them. I hear people say looping the lines will allow for more coolant flow at the back of the head. I guess its true, but it doesn't need it because it already has a port so water can flow out of the back of the head even with the heater ports capped..not to mention looping the lines would just be recirculating hot water through the engine which is counter productive.

 

[3p141592654]

the fact that both sides of the pipe in question are on the outlet side of the pump.

line from heater -> suction side of water pump (because this has alread passed through a "radiator", it is considered cold)

So was the original 'fact' incorrect?

 

[Supraguy7M]

I almost feel like my IQ dropped a few points reading all of this...

 

[CyFi6]

So was the original 'fact' incorrect?

Not exactly sure what you mean? Each quote is talking about something different. The fact remains that the both sides of the pipe from the back of the head to the thermostat housing are on the outlet side of the pump, but I see now that even though it is there can still be flow through it.

 

[3p141592654]

Your right, I did mix up the quotes. In any case, Adam writes it goes to the water outlet behind thermostat which is not the output side of the pump, its a radiator away from the suction side of the pump. The purpose was always clear though, since you need to ensure flow doesn't stagnate at the rear of the block/head.