adrianreeve
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| posted on 15/3/24 at 10:58 AM |
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Cooling an MX5 engine with a polo radiator - no rad cap on the radiator.
Hope someone can help me out. I’m using an NB 1.8 MX5 engine in my car, as many have done before me. I’m using a polo rad, as that’s 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, I’ll 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
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| posted on 15/3/24 at 12:31 PM |
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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
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| posted on 15/3/24 at 01:26 PM |
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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
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| posted on 15/3/24 at 01:30 PM |
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That’s great info, thanks very much!
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nick205
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| posted on 15/3/24 at 02:29 PM |
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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
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
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| posted on 15/3/24 at 02:50 PM |
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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
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| posted on 15/3/24 at 03:49 PM |
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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
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| posted on 15/3/24 at 06:34 PM |
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Thanks everyone - I’ve also got the VAG ball tank, so this should be a doddle!
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Myke 2463
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| posted on 16/3/24 at 08:33 AM |
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Mk 2 Clio 16mm at the bottom and small at top for bleed.
Be Lucky Mike.
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JAG
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| posted on 18/3/24 at 11:07 AM |
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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
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| posted on 18/3/24 at 11:10 AM |
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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
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| posted on 18/3/24 at 10:56 PM |
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Thanks everyone!
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cliftyhanger
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| posted on 19/3/24 at 07:18 AM |
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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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