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Author: Subject: MX5 cooling
FFMan

posted on 19/10/20 at 07:53 AM Reply With Quote
MX5 cooling

I'm curious to see what others have in terms of cooling arrangements as mine still runs hotter than i expect.

I've got a nice dual row Coolex ali radiator, coolant reroute and it still gets to 100c (on a stand lone gauge with the sensor in the now rear thermostat housing) without much effort. It's got a new stat also and it opens when i expect.

It might be my radiator stoneguard/grille is reducing air flow too much or that when i got it, the cooling system was a bit sludged up (i flushed it several times and it seems clear now) and that is still an issue ?

any thoughts ?

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Mr Whippy

posted on 19/10/20 at 11:01 AM Reply With Quote
When you say the thermostat open when you expect what temperature is that exactly? You can get them in a range of temperatures based on the effectiveness of your cooling system. You also don't say what you are doing when it gets very hot, is it sitting still in traffic or blasting along. You could also try removing the thermostat and seeing if it then over cools the engine indicating you do indeed have spare cooling capacity and that the thermostat is to blame.
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FFMan

posted on 19/10/20 at 11:07 AM Reply With Quote
quote:
Originally posted by Mr Whippy
When you say the thermostat open when you expect what temperature is that exactly? You can get them in a range of temperatures based on the effectiveness of your cooling system. You also don't say what you are doing when it gets very hot, is it sitting still in traffic or blasting along. You could also try removing the thermostat and seeing if it then over cools the engine indicating you do indeed have spare cooling capacity and that the thermostat is to blame.


i'm not sure what temp, but when the gauge is showing 100c it is certainly fully open anyway especially given the temp sensor is located in the stat housing.

In terms of use, this was just testing it running up and down an industrial estate road, so quick 500m blast, turn it round, same again. Not relentless thrashing but not road pootling either.

> You could also try removing the thermostat and seeing if it then over cools the engine

yup on my list to try. The stats tend to be quite restrictive even when open, and i run my historic race car without, just means it takes a bit longer to get to temp, but as this is a track car, i can live with that.

thanks

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Mr Whippy

posted on 19/10/20 at 11:14 AM Reply With Quote
Sure you don't have an air lock? Any time I've had over heating that's what it was, they can sometimes be really tricky to clear...
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FFMan

posted on 19/10/20 at 11:17 AM Reply With Quote
quote:
Originally posted by Mr Whippy
Sure you don't have an air lock? Any time I've had over heating that's what it was, they can sometimes be really tricky to clear...


yeah i wonder about that. When i filled it i removed the blanking plug from the thermostat housing, and cracked open the top tube on the radiator, and filled it until coolant ran out of both.

got any tips for checking/clearing ?

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chillis

posted on 19/10/20 at 12:16 PM Reply With Quote
Assuming this is a mk1 or 2 MX5 engine with a standard thermostat, then 100 degrees at thermostat outlet would be correct. Stat starts to open at 90 deg and fully open at 100 deg. Since there would be little or no flow in the top hose until the engine warmed up then the temp would appear as though it suddenly shoots up from nothing.
You could try mounting the sensor in the back of the head adjacent to the ECU temp sensor and see what you get there but the cooling system should be trying to control to 100 deg coolant jacket temp.





Never under estimate the ingenuity of an idiot!

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FFMan

posted on 19/10/20 at 12:29 PM Reply With Quote
quote:
Originally posted by chillis
Assuming this is a mk1 or 2 MX5 engine with a standard thermostat, then 100 degrees at thermostat outlet would be correct. Stat starts to open at 90 deg and fully open at 100 deg. Since there would be little or no flow in the top hose until the engine warmed up then the temp would appear as though it suddenly shoots up from nothing.
You could try mounting the sensor in the back of the head adjacent to the ECU temp sensor and see what you get there but the cooling system should be trying to control to 100 deg coolant jacket temp.


i take your point on temp.

With the collant reroute the temp sensor is next to the ecu one on e rear of the engine (NB), so about the hottest part

The original dashboard gauge shows 3/4 way over, so even the ecu think the engine is a bit warm.

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Gord

posted on 20/10/20 at 08:28 PM Reply With Quote
Mine uses an MX5 1.6 turbo, its taken me a while to get my temperatures down to a manageable level, on the track it will usually sit around 95c and may climb up to 100-103c on a hot day after being on the track for 15-20 minutes (this is soon brought down by reducing my speed for a lap, then its ready to go again.
I have made the following modifications:
Coolex 55mm core alloy radiator
Cut down intercooler to allow clean airflow to the radiator
Cowling/ducting so air is forced to travel through the radiator/intercooler only and not forced around the sides
Coolant re-route
Lots of bonnet vents to allow the hot air to escape
Making sure the coolant pipes are correctly positioned and fitted into the expansion tank
SPAL 12" cooling fan (only really used to cool the engine when at a stand)

The Coolex radiator, bonnet vents and ducting made the biggest differences in cooling for my car, as you can imagine a turbo running 14psi boost will produce a lot more heat than a na engine.
I also tried the following without noticing any difference:
Water Wetter coolant additive
Removing the thermostat

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FFMan

posted on 20/10/20 at 09:09 PM Reply With Quote
quote:
Originally posted by Gord
Mine uses an MX5 1.6 turbo, its taken me a while to get my temperatures down to a manageable level, on the track it will usually sit around 95c and may climb up to 100-103c on a hot day after being on the track for 15-20 minutes (this is soon brought down by reducing my speed for a lap, then its ready to go again.
I have made the following modifications:
Coolex 55mm core alloy radiator
Cut down intercooler to allow clean airflow to the radiator
Cowling/ducting so air is forced to travel through the radiator/intercooler only and not forced around the sides
Coolant re-route
Lots of bonnet vents to allow the hot air to escape
Making sure the coolant pipes are correctly positioned and fitted into the expansion tank
SPAL 12" cooling fan (only really used to cool the engine when at a stand)

The Coolex radiator, bonnet vents and ducting made the biggest differences in cooling for my car, as you can imagine a turbo running 14psi boost will produce a lot more heat than a na engine.
I also tried the following without noticing any difference:
Water Wetter coolant additive
Removing the thermostat


thanks some good experience there. Question, do you have stone guard/mesh in front of the radiator ? I think mine covers too much area and disrupts the air flow too much. Experience with single seaters has shown me this can be deceptive.

I think some exit vents sound like a good idea, and some shrouding round the radiator to direct the air.

I have a coolex too, i'll post a pic of the pipe layout tomorrow so you can see what you think.

i hope to go turbo next year so am aiming to keep some cooling reserve in hand but i'm battling at the minute.

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Gord

posted on 20/10/20 at 09:20 PM Reply With Quote
Yes, I use a fairly tight mesh in front of the radiator, I did think about using a larger mesh size.
Put up some pics of your engine bay, there may be something obvious to somebody.

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FFMan

posted on 21/10/20 at 09:18 AM Reply With Quote
ok some pictures - still work in progress

[img]https://postimg.cc/dL76TZHN]


[img]https://postimg.cc/SJwrLQHS]


[img]https://postimg.cc/MnVY928y]

or try these links

https://postimg.cc/dL76TZHN
https://postimg.cc/SJwrLQHS
https://postimg.cc/MnVY928y


[Edited on 21/10/20 by FFMan]

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Gord

posted on 22/10/20 at 07:27 PM Reply With Quote
A couple things that stand out to me are, your floor is fully enclosed, could this be preventing air getting into the engine bay and allowing hot air to escape.
My floor is open and I have a lot of side and bonnet vents to allow hot air to escape
The bottom pipe of your expansion tank looks like goes to the top of your radiator (it could be the angle of the pic), this should be returning to the bottom pipe of your radiator, where does the top pipe of your expansion tank feed from?
The idea of an expansion tank is to take the top feed from the highest point on your radiator and allow the bottom pipe to return the cooler water back to the lower pipe of your radiator, if you are feeding the expansion tank from two hot water feeds then this will cause overheating issues.
Is it possible to fit a cold feed to your air filter so that its not breathing in hot air from the rear of your radiator?

[Edited on 22/10/20 by Gord]

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FFMan

posted on 22/10/20 at 09:49 PM Reply With Quote
quote:
Originally posted by Gord
A couple things that stand out to me are, your floor is fully enclosed, could this be preventing air getting into the engine bay and allowing hot air to escape.
My floor is open and I have a lot of side and bonnet vents to allow hot air to escape
The bottom pipe of your expansion tank looks like goes to the top of your radiator (it could be the angle of the pic), this should be returning to the bottom pipe of your radiator, where does the top pipe of your expansion tank feed from?
The idea of an expansion tank is to take the top feed from the highest point on your radiator and allow the bottom pipe to return the cooler water back to the lower pipe of your radiator, if you are feeding the expansion tank from two hot water feeds then this will cause overheating issues.
Is it possible to fit a cold feed to your air filter so that its not breathing in hot air from the rear of your radiator?

[Edited on 22/10/20 by Gord]


thanks for the comments. not sure if you used the links to see the high res images or were working from the ones in the post ?

the floor is in fact mostly open, there is just a few inches of bodywork wrapped under. i could trim this back as that past the chassis tube is doing nothing. Pic1 shows this best

> The bottom pipe of your expansion tank looks like goes to the top of your radiator

ok - there is only one pipe on the expansion tank, and it goes to the high point on the radiator. i think my view of the expansion tank was that it was just there to accept the water as it expanded and to then run the water back in as it cooled down. sorry there is another pipe, the overflow which goes out the bottom of the car, but its the top side of the pressure cap. so if the expansion filled or got over pressure it could vent but in normal play it isn't part of the equation.

Agreed- the air filter is terrible. That bit needs work for sure.

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