9 replies to this topic

[diogoteix]

I have an issue with the flow of cooling water... we've build a "dual rad" setup, with both front and side rad (I live in Portugal, it tends to get quite hot...).
and the water is not flowing correctly (side rad cold, front rad somewhat hotter, water boiling in the engine).

The setup is the following:

- water pump is plumbed to the side radiator bottom hose the standard way.
- the side rad top hose is then connected to to the front rad (a standard MPI rad) bottom hose (where usually the water pump is plugged)
- the from rad top hose is then connected to the thermostat housing, standard way.

When I start the engine, the water temperature rises quickly to the red zone. The hoses are very hot at the thermostat, down to the front rad (less hot), and the side rad is clearly cold...

I've 2 questions:
- in which direction does the water pump flow, towards the side radiator or from the radiator to the block ?
- is there an issue of "plumbing logic" or do you think that the pump has not enough juice to pump through 2 radiators?

If it is an issue of pumping power, I may switch to an electric water pump with enough power to cope with the circuit. If not, I need to scratch my head (with your help!!)

Thanks a lot

Diogo

[Gulfclubby]

Is your thermostat stuck closed, maybe or not opening, because it is fitted the wrong way and the water is too cold? Have you tried removing it completely and see if you still overheat?

[sledgehammer]

Hi
My first thoughts on this are ...
Mini's normally run ok in hot country's , are you sure it's not something else causing the overheating ?
as the comment above - remove the thermostat to rule it out
is there a way to bleed any air from the middle water pipe - as you could have an air lock ?
also open the heater valve and check the heater is getting warm
all pipes should eventually get to roughly the same temp any cold spots are either blocked flow or more likely air
if you bleed the system , then find more air , it could be a head gasket weeping
all just my thoughts ...

[diogoteix]

The thermostat has been replaced by a blanking sleeve, so it's totally open and it cannot come from there.
As for overheating, I'm not even able to run the car more than 1 minute at iddle... So it's not an issue of "getting a bit too warm", it's clearly something wrong in the setup.

I'll try to check for air in the system, since it has quite a lot of tubing there may be some places were an air pocket has remained stuck.
My guess is that the flow of cooling liquid goes from the water pump into the engine block, then from the thermostat housing to the radiator top hose.

Since my setup is a bit more tricky, I'll try to open the hose at the top of the side rad to see if the water is arriving from the bottom rad. If not then there are 2 possible anwers: not enough "pumping power" or some issue in the tubing that needs to be fixed...
I'll let you know anyway!

[Saxo-Fiesta-Mini]

to be honest sounds like your trying to fix a problem with a problem I would just run the side fan and fit a kenlow fan kit or metal 4 blade fan. Have you tried replacing the rad cap as if its not sealing the coolant will get up to temps and the water will boil leaving no coolant
sounds like its air locking from the sounds off it
or could well be the head gasket

[mini13]

sounds like theres an air lock, I suspect at the thermostat housing,

idealy you need a small blead tube from the thermostat housing to the top of the rad, have a look at an MPI thermostat IIRC they have them.

[cambiker71]

Water is pumped from the waterpump through the engine, warms up and out the top hose into the radiator where it cools down through the radiator and back to the engine via the bottom hose. I'd do away with the second radiator piped like you have and add a second heater radiator fitted behind the grill and piped from the outlet on top of the cylinder head, fairly cheap and works very well.

[diogoteix]

Indeed, I'd forgotten that on the MPI there is an expansion tank above the whole circuitry that helps to properly fill the and "purge" the cooling circuit.
I'll check tomorrow to see how I can squeeze the air out, and I ll tell you how and if it worked.
Thanks for your tips

Diogo

[ibrooks]

I'm not even able to run the car more than 1 minute at iddle...

STOP!

A car will not overheat in one minute - even if you connected the cooling hoses directly to each other with no radiator. If this is the only evidence of "overheating" then you need to start thinking where the problem is. If the temp gauge is going into the red after one minute then it's lying to you. Get that sorted before you start further mucking around with the cooling system (but see below).

I'll agree that you seem to have a problem with the cooling system though from the symptom of one hot area and a cold area. Try to keep it simple. Remove the second radiator and run a standard cooling system. Even on the most highly tuned motor and in the hottest climate this WILL cope with the heat and at least let you drive the thing. It might run into problems if you spend long periods stuck in traffic but at that point a twin-core standard radiator and better/additional fan will do the job. Adding a second radiator has just given you an additional potential problem.

Iain

[Aria Aradhea]

Yes, I agree...

I use a good quality 2-core radiator from Minispares, 6-blade metal fan and electric aux-fan with the thermostat replaced by a blanking sleeve. I'm from Jakarta, Indonesia where the climate is very hot and the traffic is like hell - literally - and also use air con for most of my driving. During the hottest day, aircon on, the temp will go about until slightly below 3/4 on the gauge. Get some speed, and it will quickly go down to 1/2. If I don't use the aircon, it will happily stay at around 1/2 in a traffic jam.

So, the side-mounted setup works really well even in the worst condition and it's simpler too...