Hi All,

I have had my Rossa for a month or so now and ironed out a few niggles. With the winter coming its time to put some anti freeze into her. Currently it has just water. I am worried about draining the system down and refilling with anti freeze mix as I may airlock the radiator.

What I am hopping some one can help me with it as follows :-

1. What is the best way to bleed air from the rad? I am thinking about fitting a bleed valve on the top hose near the rad but there isn't much space.

2. how much water does the car hold? Maybe I will drain the correct amount and replace with anti freeze.

Thanks

Richard

From my experience although its coupe based.


Your thoughts on the rad will help. I have a swirl pot that my top hose runs through with is as high as I can get it within the engine bay and a bleed at the top of my rad.

When I fill my system I connect my bleed to a jug and continue to fill the system allowing the bleed to almost fill the jug while I fill the system. Once I have about 3/4 of a litre in the jug, I cap off the bleed and continue to fill.

Run up the car with cap off allowing to warm up and open the thermostat. causing the water to flow through the system. If you want it may be worth raising the rpms to 2k to pump the water around, be aware the water level may overflow the header tank slightly especially if it burps and some air come out, top up if required.

Shut off allow to fully cool and top up I usually do another bleed on the radiator at this point.

Neil

My Rossa took 8.5 litres from dry - the Metro donor took just 8.5 pints! Shows just how much extra it takes with a front mounted rad and rear mounted engine. I increased the pipe diameter while I was at it which explains some of the difference but I'm not sure if that was a good idea because the coolant now flows through the rad faster so might not be getting enough time to cool properly (the fan runs for ages so I might try fitting a second one).

When I fill it I open the heater valve, jack up the rear of the car as high as I can, remove the thermostat and put the coolant in slowly via the thermostat hole in the cylinder head. I've done it several times this way and never had any problems with air locks etc.

Your engine is probably an A+ with no bypass hose between the head and water pump so if you have the heater fitted and also a valve to shut off the water to it you should drill two or three 3mm holes in the thermostat to keep the water flowing when the heater is shut off. I believe that later heaters have a different valve with a bypass in it to keep some circulation going when the heater is off but the old Mini heaters as fitted to Rossas don't have this so the coolant can't circulate properly round the engine when the thermostat is closed and numbers 3 and 4 cylinders overheat. Drilling holes in the thermostat prevents this from happening. This is also the reason why you need to fit a blanking sleeve if you run without a thermostat http://www.minispares.com/product/Class ... ostat.aspx

Thanks for the interesting replies chaps. I have a few questions and comments :-

1 What is a swirl pot for?

2 I think I will try to fit a bleed valve up front. Dose your rad have the bleed or have you managed to fit one somehow? I was thinking about cutting the top hose and inserting a short piece of copper tube with a bleed valve brazed in the top.

3 I have read about the too high water flow through rad scenario before. I don't understand how too much water flow decreases the cooling effect of the rad. Cooling effect is governed by several factors including the temperature difference (Td) between the water and air. with a lower flow rate the leaving temperature will be lower than with a higher flow. Therefore the average Td is less so less heat transfer will occur between the water to the air. It is easy to make the mistake, that due to the cooler leaving water temperature with a lower flow rate more heat is being dissipated, forgetting that you are cooling more water with a higher flow rate. (Q=M C Td ( Q-heat quantity M-mass flow rate C-specific heat capacity of water/antifreeze Td-temp difference across rad)). I'm not sure how this equates to fan run time. Maybe due to the extra mass of water to cool will take longer. Does the fan stay off for longer as well?

4 Yes I have an A plus engine. I will check the thermostat and heater valve stuff. The car never reaches more the 1/3 on the temp gauge so I was going to fit a new stat. Come to think of it I don't know if the car has one fitted

I don't have a bleed valve fitted anywhere. As I was led to believe, the water is passing through the rad too quickly to be cooled properly by the airflow which does have a logical ring to it. The original Metro hose from the thermostat housing is also a reducer but I kept the same diameter all the way through - the reducer must have been there for a reason. The extra fan plan is to give better coverage of the radiator while sitting in traffic and there is no ram effect. The fan doesn't seem to take any longer to come on but takes ages to go off again, as I said, particularly so on hot days when it seems as if it could run for ever. I sometimes wonder, too, if the restricted space behind the rad is also restricting the air flow.

I managed to get the Rossa water bled from the rad, ages ago.

I fitted a tyre valve to the top hose. I lost the photo but finally found it.

Makes bleeding very easy.

Tidied your post a little for you Richard.

looks good, make sure you have a well fitting metal dust cap with rubber seal fitted when in use, as when the system cools and tries to go into vacuum you don't want the valve to let any air in

Neil

Thanks for the tidy up I did have a little trouble getting the photo up.

Yes I did fit a nice valve cap. Good point about the vacuum. I was more concerned about it leaking coolant out. The header tank cap should let air in before a tyre valve. Better safe than Boiled up on the side of the road

Talking about boiling up, I had a MGF that kept boiling in traffic. After replacing the blown fan fuse and faulty relay the car still boiled before the fan came on. Turned out the pressure cap had fallen apart and the system was not pressurising. Guess what temp the fan cuts in at. 105C ! Would it be so bad for it to come on at 95?