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Author: Subject: Cooling an MX5 engine with a polo radiator - no rad cap on the radiator.
adrianreeve

posted on 15/3/24 at 10:58 AM Reply With Quote
Cooling an MX5 engine with a polo radiator - no rad cap on the radiator.

Hope someone can help me out. Iím using an NB 1.8 MX5 engine in my car, as many have done before me. Iím using a polo rad, as thatís what will fit in my nose one (again, not breaking any new ground here!). Can someone help me understand the coolant pipe routing for this arrangement please? MX5 rads have an integral cap, so the header tank is just an overflow tank really. As the polo rad has no cap, Iíll need to use a pressurised header tank instead, but have got myself confused regarding how I will plumb this in. Has anyone got a diagram or couple of photos of how they have done theirs please?

Thanks very much, Adrian

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cliftyhanger

posted on 15/3/24 at 12:31 PM Reply With Quote
No pics, but doing something similar in my Dolomite with a golf rad.

Ideally you need a take off the bottom rad hose 16mm or larger, and somewhere on the engine, ideally highest point, a small takeoff. The expansion tank needs (obviously) 2 connections, large at the bottom, small at the top. This will allow coolant to flow through the expansion tank, removing air.

I am using a Corsa tank, woth one of the 2 top outlets blanked off as its shape works with my install.

Others may have ideas on how to do this. But I have used the same system with a st170 in my spitfire with a golf rad, and that works beautifully.

[Edited on 15/3/24 by cliftyhanger]

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jps

posted on 15/3/24 at 01:26 PM Reply With Quote
Worth a search of previous threads, i have seen diagrams in the past on here - from memory there is more than one workable solution...
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adrianreeve

posted on 15/3/24 at 01:30 PM Reply With Quote
Thatís great info, thanks very much!
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nick205

posted on 15/3/24 at 02:29 PM Reply With Quote
Can't help you with pipe routing.

I built a Pinto engined MK Indy, used a Polo rad (for the same reason) and an expansion tank (see image).

Description
Description


IIRC the expansion tank was 2nd hand from a Polo or Golf. Screw on cap to allow filling of the cooling system.

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Slimy38

posted on 15/3/24 at 02:50 PM Reply With Quote
I plumbed mine in no more than a couple of weeks ago, this is what I did;

32mm hose from radiator to water pump.
32mm hose from radiator to the original engine rad connector. In this pipe I added a T connector with an 8mm T, as high as possible. I also used a 90 degree bend near to the engine as it's a bit of a tight bend.
16mm hose to complete the loop on the heater matrix side of the engine. In this pipe I added a T connector with a 16mm T.

I also got myself one of the VAG 'ball' coolant tanks. They're pretty much universal for anything coming from VW, Audi etc.

The 8mm T connector goes to the overflow of the coolant tank, and the 16mm T goes to the feed of the coolant tank.

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ianhurley20

posted on 15/3/24 at 03:49 PM Reply With Quote
quote:
Originally posted by Slimy38
I plumbed mine in no more than a couple of weeks ago, this is what I did;

32mm hose from radiator to water pump.
32mm hose from radiator to the original engine rad connector. In this pipe I added a T connector with an 8mm T, as high as possible. I also used a 90 degree bend near to the engine as it's a bit of a tight bend.
16mm hose to complete the loop on the heater matrix side of the engine. In this pipe I added a T connector with a 16mm T.

I also got myself one of the VAG 'ball' coolant tanks. They're pretty much universal for anything coming from VW, Audi etc.

The 8mm T connector goes to the overflow of the coolant tank, and the 16mm T goes to the feed of the coolant tank.



In 2016 I did exactly the same and would get my vote again (in fact this is eactly what I am now doing with my MX5 engined Dutton Legarra)

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adrianreeve

posted on 15/3/24 at 06:34 PM Reply With Quote
Thanks everyone - Iíve also got the VAG ball tank, so this should be a doddle!
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Myke 2463

posted on 16/3/24 at 08:33 AM Reply With Quote
Mk 2 Clio 16mm at the bottom and small at top for bleed.





Be Lucky Mike.

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JAG

posted on 18/3/24 at 11:07 AM Reply With Quote
This is my 1.6 MX-5 engine, with a Polo Rad' and an Expansion Tank



The Expansion Tank is on a T-junction taken off the lower Rad' hose.

[Edited on 18/3/24 by JAG]





Justin


Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!

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JAG

posted on 18/3/24 at 11:10 AM Reply With Quote
another picture.

The car has been in use for over 10 years like this. It has never given me any trouble with engine cooling. I used the Fan Switch screwed into the Polo Rad'

The only thing I changed since these pictures were taken is that I removed the Heater. I simply plumbed the two pipes, exit from and return to the engine, to each other with a short length of rubber hose.




[Edited on 18/3/24 by JAG]





Justin


Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!

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adrianreeve

posted on 18/3/24 at 10:56 PM Reply With Quote
Thanks everyone!
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cliftyhanger

posted on 19/3/24 at 07:18 AM Reply With Quote
Just a thought, but a rad cap adaptor to go in the top hose can be used
https://www.ebay.co.uk/itm/283375738575

You would need to ensure teh cap has an upper seal, and fit a non-pressurised expansion bottle (like all the jap cars seem to have) with the hose terminating at the bottom so coolant is sucked back as the engine cools.

But an expansion tank with a bleed is a better solution, as long as the bleed is at the high point.

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