schematic diagram of cooling system
 

hi , does anybody have a diagram showing the directional flow of the cooling system ? .
my reason for this is , i have changed my rad and fan ( thanks for the kenlow jules ) cleaned out the matrix removed the engine drain , refilled the cooling system with oat , still not getting red hot air out the heater .
i have also done a mod on the cooling rail , car is not overheating and running fine,but the bottom cooling rail is not getting as hot as it should i think ...
so i now think that the problem lies with the thermostat not allowing the coolant to circulate ?

sometimes the heater blows warmish air on low fan , but i think when its on fast because the flow is not good enough the blower is cooling it down , without the fan on both flow and return on the matrix are red hot .
your thoughts please thanks mark

It sounds like an air lock in the heater circuit to me, but I'm intrigued by your 'mod on the cooling rail'. Could that be connected to the problem?

TC

the mod to the cooling rail was done with silicone hose and two sections of stainless steel with the ends beaded over , my mild steel rail was in very poor condition and xpart said they did not have a stockist any more..... i refilled the cooling system with nearly 8 ltrs of mix and allowing for over spill from bleeding is near as dam the 7.2 .

have read of several posts of fellow members who say they have no air lock but heating is not good , even members who have used the pella.

just thinking that there is a different problem that we are missing , so does the thermostat control the flow round the system . my water pump was replaced approx 39 k ago with belts ...

if everybody thinks its an air lock , i have to take there advice as i have only owned the car for 2 months and most of you have been tinkering with these cars for years .

if thats the case then will hhave to try and get hold of a pella or take a trip to lates , how much do they charge to empty and refill a system ( ball park figure ) cov not to far from me .... i wonder if they are open over the bank holiday , this is doing my head in now :(

Drain and refill no more than half hour using a vacfill.Cars queueing at the moment until end of May

i very much doubt its the thermostat, if it wasnt opening you would certainly know about it, as the engine would quickly overheat. however, if it was stuck open, your engine wouldnt get upto temp. thermostat allows coolant to circulate around the engine once open, nothing to do with the heater matrix. when the thermostat is closed, the water inside the engine and the heating system is allowed to heat up, which is why the heaters should blow warm before the thermostat opens. once to the correct temp, thermostat opens and coolant flows through the engine.

within the dash, there are control flaps, which basically mix warm and cold air so the temp on the atc unit is near enough what is coming out of the blowers. sounds like either the temp sensors is broken or reading wrong, the flap which controls warm is stuck closed/partially open, or the flap which controls cold air is stuck fully open, if there isnt any air in the heating system.

thanks robson, have covered over 300 miles and no overheating or coolant loss :) , which temp sender ? thanks mark . will keep that in mind thanks lates

im not sure tbh, there is a bumper mounted one, however, if the temp on the display between speed and revs is correct or fairly close, it wont be that. there is also a cabin temp sensor, and if thats playing up then it wont be delivering the selected temp on the atc. the sensor is behind the steering wheel at sort of the 7 o'clock position, but i have no understanding of these. apart from the sensor and the air delivery, i cant think of anything else

outside temp sender working ok , will do a search for the cabin one ty :)

Is the pollen filter in working condition?

TC

The in-car temp sensor is behind the lil oval thing with horizontal slots to the left of the steering wheel and approx 9 inches below the temp guage. I assume that should that get blocked in some way, the ECU will not be getting the correct in car temp readings and may restrict the heat to the car interior.. This is just guess work. But as air passes through it, it's worth checking and cleaning anyway. :}.
...

not sure about the pollen filter , have just checked the service history and last time it was changed was over 3 yrs ago .
would this affect the heating ?

will check the sensor tomorrow :)

Firstly if problems with heaters, always first check and see if you have enough water in the system. But you seem to have done that, so let's go to the next issues!
There are times where the cooling from the heater alone is more than what the engine needs to keep cool. This happens especially in cold wet weather, where the windchill factor is high. The natural cooling of the engine from the air flowing around it is high, and the heater inside the car is on maximum.
The thermostat in this case does not come into the picture, because it stays closed, and all the cooling happens via the natural cooling and via the heater which bypasses the thermostat. IOW the hot water to the heater is taken from the cooling system from an outlet that is not controlled, and therefore always fully open.
Note that if you use your demister, you heater works on maximum, even if not "switched on". In that case the system cools the air with AC to maximise moisture extraction, and heats it maximum to increase moisture absorbtion from the front screen.
If the heater does not come up to temperature, try and switch it off. Switch the fan off, and let the engine heat up. Switch the recirculation on. In this case you have minimized the cooling. (it is unknown to me if there is inded a valve, as in older cars, which will open/block the flow through the heater matrix, I some how have a feeling there is not) The temperature of the engine should increasse. You can then switch the heater on partly and keep some heat coming out. If you switch it on fully, again you will cool the engine down, so it is a balancing act. Too much and it gets a lot but cold, less and it gets warm.
There seems to be a lot of this around and one reason is undoubtedly the cold winter.
If this is your problem, you will typically find that the heater works when the engine is labouring hard at low road speed. The worst situation is high speed, low load, like a decline on a highway.
Contributing factors can be mechanical faults and there has indeed been som write ups on these. As so often before, many people do not bring up the conclusion, if there was indeed any, as in the tread below:
http://www.the75andztclub.co.uk/foru...ht=heater+flap

you most certainly have air in the system , when you refilled the system did you have the heater set high?. ito get of air and gunk from my system i un did top and bottom hose and ran a hose pipe through top hose allowing water to go right through system ,you wouldnt believe the muck that came out .. then filled it up and bleed it .you will need someone to top up while you bleed it as it takes a while for the air to escape .the lower the level gets the more air you will get in system .. mow i got a nice hot heater and no more over heating issues or hoses splitting cos of the prusse build up due to the air in system and coolant not being able to circulate around the system ...remember bleeding the system is not about letting the over fill of of coolant out to obtain the right level of coolant .to get rid of all the air it can take you up to an hour .when the air was all out my car the coolant flowed out the bleed value in one movement not slowing and speeding up and slowing again ..

tried everything, one thing i have noticed is when i remove the expansion cap to check the coolant level in the morning i get a hiss of pressure relief on a stone cold engine, so the system must be ok . unless this is not normal and the air lock is slowly moving up to the tank :shrug: and i am letting it out when i remove the cap :shrug:

That doesn't sound so good to me to be honest. A stone cold engine cannot have residual pressure in the cooling system unless it's permanent gas that's been put in under pressure. That means a gas like CO2, in other words, exhaust gas. It would explain all your overheating/bad circulation issues.

TC

mmmmm no mayo around at all , and she runs like a dream . i understand what you are saying , but if there were gasket or failure of something else surely there would be signs of some sort ? have run the engine with the cap off untill the level rises and put back on , there were no sign of air coming up . where could i get one of those water co2 testers from :shrug: local motor factor shop

Most garages should be able to do the 'sniffer test' to detect exhaust gases in the coolant. I dare say you can buy such kits on eBay.
I'm thinking a cracked liner perhaps? A one way pump action?

TC