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Heater Matrix bypass - a definitve answer?


Bossco
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I've just read Turtleshead's thread about his heater matrix bypass on Friday and it reminded me of a question I've been meaning to ask for ages.

Is there a definitve answer regarding heater bypass do's and dont's? Should the pipes be joined up or should they be blocked off?

I read loads on past threads about this and the various arguments regarding HG failre but I never found a definate answer. Thankfully I'm no longer suffering overheating problems so it's not an issue for me, I was just wondering.

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If I was doing it I would definitely block them off. Joining them up will leave a flow area with no resistance, therefor the coolant will take the easy route dropping the flow in other areas of the system.

 

With the matrix in place it will put a resistance in the flow, which I'm guessing is calculated to keep the system balanced.

 

That's just an opinion though, not a definitive answer. I'm curious of the reasons behind both solutions :)

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Well history seems to indicate that HG failure followed many bypass jobs but no so many block off's. To me, it would make more sense to bypass it and join them up, that way coolant is still flowing round the full system. I've been looking at the coolant system diagram and I've read a few technical explanations which support blocking them off but to be honest I didnt fully understand them.

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Well history seems to indicate that HG failure followed many bypass jobs but no so many block off's. To me, it would make more sense to bypass it and join them up, that way coolant is still flowing round the full system. I've been looking at the coolant system diagram and I've read a few technical explanations which support blocking them off but to be honest I didnt fully understand them.

 

 

I'll do a crappy diagram to show my thinking on it.....

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I have been running blocked off for a long time, before that I bypassed with restricted pipe I made up.

 

I agree with Scott, looking at the workshop manuals flow diagram blocking is better as it forces all the coolant through the head instead of around it ;)

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To me both solutions seem extreme... could you not use a bit of pipe with a restriction (either thick walled, squashed nearly flat or washer welded to one end) to join the pipes that would allow a small flow. That way would mimic the average flow of the heater matrix and avoid any problems.

 

Still not definitive tho...:search:

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To me both solutions seem extreme... could you not use a bit of pipe with a restriction (either thick walled, squashed nearly flat or washer welded to one end) to join the pipes that would allow a small flow. That way would mimic the average flow of the heater matrix and avoid any problems.

 

Still not definitive tho...:search:

 

That would work as well, but there is no reason to have a restricted flow going round a couple of pipes leading to nowhere. It's pointless cooling the pipes that don't go anywhere ;)

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Scott, your picture gives a much more clear explanation than the "official" coolant flow diagram that toyota provide. Am I right in thinking that when your heaters are set to blow cold or turned off then the coolant flow would mirror the top, blocked off image?

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Scott, your picture gives a much more clear explanation than the "official" coolant flow diagram that toyota provide. Am I right in thinking that when your heaters are set to blow cold or turned off then the coolant flow would mirror the top, blocked off image?

 

As far as I am aware that is exactly how it works. It's a valve inside the matrix that blocks off the intake.

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Yeah I know the valve, I can sometimes hear it click when it opens up. A while back the heaters were not warming the car as well as they used to, while Hodge was tinkering under the bonnet I was inside the car, I heard the click and then the hot air came blasting out. Part of my confusion is connected to this, as water temps seem to drop when the heating is on in most cars, however if the block off method is used or the heating is set to cold then this should be providing better cooling, thus reducing the temps?

Edited by Bossco (see edit history)
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Yeah I know the valve, I can sometimes hear it click when it opens up. A while back the heaters were not warming the car as well as they used to, while Hodge was tinkering under the bonnet I was inside the car, I heard the click and then the hot air came blasting out. Part of my confusion is connected to this, as water temps seem to drop when the heating is on in most cars, however if the block off method is used or the heating is set to cold then this should be providing better cooling, thus reducing the temps?

 

The reason that the heater being open cools the system so well is because it's like a big radiator/heatsink with a fan on it. This cools the temperature of the liquid. With the bypass method the temperature that the sensor sees will probably be the same as with the ports blocked. The trouble is the core of the head will be a FAR higher temperature due to the coolant not flowing over that area. The problem isn't that the coolant overheats with the bypass method, the problem is that the critical areas of the head aren't getting any flow and thus overheating/warping/cracking etc.

 

My say do you follow?

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I could be way off here but I seem to remember reading (about 5 years ago!) that the heater always flows a bit of hot water through it and uses a flap to direct the cold air via a bypass????

 

Anyone verify this?

 

I don't think it works that way. Simple test is to put your heater system to cold and check the temperature of the "out" port :)

 

If I'm mistaken then the bypass will most definitely be restricted.

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Here's the heating diagram which shows the Air Mix Dampers around the heater core...

 

At the moment mine still has some air in the system so I can hear the fluid flow through the heater when I give it some boost - happens when the heater's on cold too???

heater diagram.jpg

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