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Author: Subject: Heater plumbing question
John Bonnett

posted on 15/10/22 at 08:43 PM Reply With Quote
Heater plumbing question

The Project is fitted with a 1.6 Ford Sigma engine and the question relates to the plumbing of the bypass. In this case, the hot water pipe to the heater has an electrically operated hot water valve controlled automatically from the climate control module. There could be a situation when on start up in hot weather for instance, the hot water valve might be closed and this would prevent any coolant circulation until the thermostat opened.

What are your thoughts on having a permanent restricted bypass or indeed, any other solutions.

Thank you.

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ianhurley20

posted on 16/10/22 at 08:38 AM Reply With Quote
On the MX5 the heater matrix is always full flow and flaps used to regulate airflow. I didn't use the MX5 heater sytem but used the same principles and am going to do the same with my current MX5 based project. Both with 1.6 Mk 2 engines






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John Bonnett

posted on 16/10/22 at 09:10 AM Reply With Quote
Thank you Ian and nice to hear from you.

I think we'll be okay without any extra plumbing because there is a small bore take-off from the back of the head which feeds into the header tank shown on the attached diagram and confirmed by looking at my engine. This should do the job when the heater valve is closed.

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obfripper

posted on 16/10/22 at 11:34 AM Reply With Quote
IIRC the original fiesta valve is 3 way, it should flow through the radiator when on hot, and bypass back to the lower/secondary hose when set to cold.
There is no hot/cold flap on a mk4 fiesta heater, so this is the only heater control used on the original heater.

I take it your replacement a/c heater box uses a similar system, but with a 2 way valve?

I would also place the header tank lower hose into the radiator lower hose, with it into the top hose the radiator will always have some flow passing through, and will slow down the engine warmup.

Dave

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John Bonnett

posted on 16/10/22 at 12:17 PM Reply With Quote
quote:
Originally posted by obfripper
IIRC the original fiesta valve is 3 way, it should flow through the radiator when on hot, and bypass back to the lower/secondary hose when set to cold.
There is no hot/cold flap on a mk4 fiesta heater, so this is the only heater control used on the original heater.

I take it your replacement a/c heater box uses a similar system, but with a 2 way valve?

I would also place the header tank lower hose into the radiator lower hose, with it into the top hose the radiator will always have some flow passing through, and will slow down the engine warmup.

Dave


Thanks Dave,

Yes you're right, the Fiesta valve is three way but I'm using the Dakota Digital valve which is part of their climate control unit. This is just an in-line valve electrically operated.

Feeding from the header tank into the bottom hose was always the plan. I used a similar system on the lightweight and it worked really well.

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