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Old 08-06-2012, 10:10 PM   #1
windymiller
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Default 4age cooling problem

Hi guys, I'm having issues with the cooling of the 4age which I've installed in my mini. The cooling system is pretty standard except the rad is from a Nissan Micra. Now before you all shout 'fit a bigger rad' hear me out:

When driving on a flat dual carriage way at up to 3500ish rpm, its fine. Up hills it will start getting warm. If I sit at 3500-5500ish rpm, it gets almost to the red. Over 5500rpm, it cools down a bit but is still near the red. If I sit at 5500rpm with it near the red and floor it, the needle actually drops as if its had a shot of cool water through the engine.

I'm wondering if the cool water in the rad isn't getting circulated very well? Can anyone help with this? I need to get it sorted as I've got a DTA ecu and ITB's waiting to be fitted, but there's no point if I can't keep it cool
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Old 08-06-2012, 10:38 PM   #2
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The micra rad is pretty thin, maybe it doesn't have enough capacity.
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Old 08-06-2012, 10:57 PM   #3
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Originally Posted by l_jonez View Post
The micra rad is pretty thin, maybe it doesn't have enough capacity.
That was my first thought as the micra rad is wafer thin, but the dip in temp when I floor it at 5500rpm has puzzled me. Maybe they're two unrelated issues? I'm struggling to find a bigger off the shelf rad that'll fit as the dizzy sticks out the front of the head and gets in the way:



Any ideas? I did try a Pug 206 rad with one end uncrimped and turned upside down, but the top pipe was sqeezed between the dizzy and alternator and would have rubbed through eventually. If I fit the DTA ecu I can get rid of the dizzy, but I'd like to sort the cooling before I start looking for more power.
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Old 11-06-2012, 08:18 AM   #4
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Guys out in South Africa use the 1600 VW Citi Golf (Golf 1) rad as they are big and dirt cheap.
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Old 11-06-2012, 09:29 AM   #5
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air lock in your cooling system? water pump failure?
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Old 11-06-2012, 06:36 PM   #6
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Nice work
are you still running a thermostat ?
where is the sensor located im thinking maybe there is a hot spot developing but doesnt explain everything
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Old 11-06-2012, 09:48 PM   #7
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I've got a new water pump somewhere that I could try in case the old one has gunked up. There is a possibility of an air lock as the rad bottom hose has a hump in it which could trap air. The thermostat was new when I fitted the engine and the sensor is in the standard place and it feeds the standard MR2 gauge.

I think I'll try the following for now before I look at fitting a bigger rad:

1. Remove all hoses and clean
2. Replace water pump
3. Re-route hoses to eliminate air locks
4. System flush
5. Replace coolant

Is there anything else I should look at?

If I replace the coolant, is it worth increasing the percentage of coolant? Maybe 80%?
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Old 12-06-2012, 03:10 PM   #8
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silly qweastion but someone has to,lol are you judging by the geuge alone? they have been untrue before,or do you know its getting that hot,as in you feel it boging or cant put your hand on it?? i would hate for you to do all that work for nothing,
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Old 12-06-2012, 10:56 PM   #9
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Thats a good question and not daft at all! I'm going by the gauge alone. It has got hot in the past and sprang leaks from the increase in pressure (leaks now cured and system topped up) The gauge shows cold during warm up, then steadies in the mid or normal position when its at running temp with the thermostat open. its only when its at running temp and there load on the engine such as half throttle when going up hill that it increases. All this suggests that the gauge is working as it should. It may be worth mentioning that according to the power graph I have, the engine produces the same power at 3500ish rpm as a Micra does, so maybe its just the rad that can't cope? My brother had an infra red thermometer that I can borrow which should give me a good idea if the gauge is telling the truth.
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Old 13-06-2012, 12:47 AM   #10
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yes i see ,maybe you need a smaller pully on your water pump,its the last thing to change/the pump that is,,in the sceem of it i dont mind not useing a thurmostate at all but look into your engines reqwirements,,its i matter of the wallet/spending so think before going madd,lol,any weard bumps in the system wont help,,the uphill thing is a worrie coz i have a subaru with a water problem,its doing my head inn,it will runn all day long ,butt if you look at a hill and put it under load it boil,s.its surely a head problem,regards shaun
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Old 23-06-2012, 07:43 PM   #11
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Well, I've found the time to have a fiddle with the cooling system with some success. The hose with the hump has been replaced with a hump free hose. I also found a small leak from the hose from the thermostat to the pump. This leak seemed to drain water from the back of the engine, but not from the radiator. This meant that although the water level in the rad was fine when checked, the system was actually low on coolant. I've now cured the leak, topped up the system and bled it thoroughly and been out for a 'spirited' drive. The cooling is now massively improved, but I may still look at fitting a bigger rad.
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Old 23-06-2012, 08:02 PM   #12
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Ardonfast, the waterpump impeller vanes could be erroded away.

A few years ago I fixed an A+ Metro with the same symptons as your scooby, the vanes were completely missing/dissolved.
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