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Overheating S7


Misternomer
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HI everybody.  I am a new member and have just bought an 2000cc pinto S7 with my son and we are having some shakedown issuesadd with overheating.  The previous owner was a builder of BRM racecars and seems to have done a great job with the exception of cooling issue.  Basically we heat up to 90norm in minutes and starts to overheat after more than a few mins in traffic.  Even when running at 50mph on a cool day (14c ambient) - it never really shed the head and sits between 100-110c

 

Shortly before selling, previous owner fitted a new twin core aluminium radiator, and a small electric fan on an isolated switch, which we always leave turned on.

Hypothesis is as follows:

 - Looks like the electric fan (see photos ) is far too small.  It's only 6" diameter can't be much use.  How big should this be?

 - What happens if polarity is reversed and the fan isn't pulling air through (haven't checked this yet)

 - There is no expansion tank that I can find.  This surely must limit the thermal capacity of the coolant

 

Installing a larger fan seems problematic as there is 1.25" clearance to the front of the crank pulley.  Any advice on fault-finding on a workable solution would be very much appreciated

 

62498318874__95471A9E-0FA1-4556-B7CC-AFE02F21E752.jpeg.dfc1f9cdcd2ca4953d99ffb6871648ab.jpeg

 

62498315828__E97C2631-32FB-460C-959E-1992E73A89BE.jpeg.ec3159c499d35c8e7927019111726566.jpeg

Edited by Misternomer
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If running in free air at 50 on a cool day it is still getting warm, then there is a larger issue than the fan.  The fan should really only come on in traffic and (if suitable sized) should provide enough airflow to cool the temps back down.

To answer your questions:
A small fan can still have impressive flow, but that does sound small.
If polarity is reversed the fan could be fighting the flow coming into the engine bay - this could be part of the problem.
Expansion tank should be necessary. 

Have you got a heater plumbed in? or if no heater, does the heater connector on the manifold route back to the water pump?
Is the thermostat opening correctly? if it is stuck closed you wont get adequate flow through the radiator to cool the engine.
Have you got a louvered bonnet? or any other ways for hot air to escape? Under bonnet temps can be a big factor in causing overheating issues.
 

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 - it has a twin core race rad with a top and bottom tank and a cap on top, so I don't think it strictly needs an expansion tank

 - at 6" the fan is only marginally bigger than a CPU fan.  I spoke to a pinto specialist at HPE performance in Maidstone and he recommended moving to a 12-14' Spal fan.  Said the eBay jobbies comminly only have ⅓ of the flow rate of a Spal

 - Yes the bonnet is louvred's

 - There is no heater

 - I will swap out the stat for one I know to be 82c low temp version

 

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Spal fans are great and come in a range of sizes, both diameters and depths. They also have a massive range of flow rates, worth paying close attention to the specs and getting the highest flowing one you can in a size that fits, because amazingly the price differences between a low flowing one and a high flowing one are negligible.  Also when it comes to buying a fan I can highly recommend airconco, there website has all the information you need to make a decision on which fan and they are very well priced https://shop.airconcoparts.co.uk/epages/es117975.sf/en_GB/?ObjectPath=/Shops/es117975_shop/Categories/SPAL_Fan_Section/Axial_Fans_12v

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Be good to see pics. In my experience with seeing cars that have overheating issues it is almost 90% of the time down to bad air flow design. Failure to control the consumption of air into the nosecone and THROUGH the radiator (by ensuring there are no lower-pressure routes around the radiator instead of through it), and likewise blocking the flow of air once it's gone through the radiator - blocking the back of the rad, or not giving the air any suitable low-pressure exit route out of the engine bay.

It could still be bad rad, blocked channels, knackered 'stat or whatever, granted, but if I was generalising, I'd go with the above.... ;)

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20 minutes ago, theduck said:

Also when it comes to buying a fan I can highly recommend airconco

Thanks  - that's really useful.  The current fan only covers about a 3rd of the SA of the matrix.  I am worried about clearance against the crank pulley, but both Spal and Airconco look incredibly thin

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21 minutes ago, brumster said:

Be good to see pics. In my experience with seeing cars that have overheating issues it is almost 90% of the time down to bad air flow design. Failure to control the consumption of air into the nosecone and THROUGH the radiator (by ensuring there are no lower-pressure routes around the radiator instead of through it), and likewise blocking the flow of air once it's gone through the radiator - blocking the back of the rad, or not giving the air any suitable low-pressure exit route out of the engine bay.

It could still be bad rad, blocked channels, knackered 'stat or whatever, granted, but if I was generalising, I'd go with the above.... ;)

do the pics you can see in the OP help at all?  I can confirm that it definitely IS overheating - stinks, steams and splutters out the cap!

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Looking at those pics the pipe run appears a bit convoluted.

Do I see right the hose from the thermostat housing is going to the bottom of the radiator and the hose from the top of the radiator going round the front of the rad and presumably to the engine bottom connection.

This would put the radiator into reverse flow with all the flow stagnation problems this gives in the radiator.

Normally you would run the thermostat outlet into the top of the radiator to work with thermocycle of the coolant rather than against it.

With this run i would expect it to be hard to bleed all the air from the system.

With the lack of room is it possible to mount a fan in front of tha radiator pushing air into the radiator?

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24 minutes ago, IanS said:

Normally you would run the thermostat outlet into the top of the radiator to work with thermocycle of the coolant rather than against it.

 

Thanks Ian.  This makes a lot of sense - I'll post some more detailed photos later when I get a chance  - so if I am understanding you correctly - the optimal flow would be 

engine-bottom_to_rad-bottom_to_thermostat housing(top of rad)_to_engine top connection

in other words the coolant is flowing up through the rad cores ensuring the air stays at the top of the rad and the coolant flow is sympathetic to the convection flow.

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