Cooling system

[PeterCrespin]

That's Orstraylyuns for you... It was probably removed around 1977 to stop up a leaking dunny can somewhere in the outback. Good for the dunny, sh*t for the Jag..

Alternatively,

"Hey Bruce, me thermostat's busted. What the hell do we do now out here?"

"No worries mate, there's a spare one in the left side housing."

"Bugger me! Think of everything those bloody Poms eh?'

"No thanks mate. Yeah, everything except winning at sport, sport."

[Rustyred]

Peter, That's pretty funny and possibly on the mark as well.
It's good to see you have a good sense of humour.

But more likely, once the car got out here, back in the day, the engineers maybe thought we have no need for 2 thermostats. Would be interesting to see if other Aussie versions had only 1 Thermostat.
It only gets cold in the Snowy region and Canberra in Winter.
Lucky we have no councils that lay down salt on the roads , so that you end up with a rusty pile iron ore in the wheel arches, sills and floorpans.

[AussieEtype]

Well in 1977 my car was still back in the homeland - some Pommie up around Peterborough decided my car did not need the second thermostat.

[Lambo911]

Still need to look at mine, will do it tomorrow.

It's a UK supplied car which spent 1983 to 2000 in Johannesburg....

[Lambo911]

OK all sorted I think.

Yes the car did have two thermostats and they are both working.

I added a couple of bottles of rad flush and drove the car for 15 minutes. The temperature crept up as before.

I then let it cool off and flushed the system through, back flushing through the rad resulted in quite a lot of small brown particles. I then took the rad out so I could turn it at various angles whilst running water through it.

Stuck it all back in and ran it with pure water to check it was ok which it was with water flowing through the radiator and this time the fans were cutting in.

I then put the thermostats back in added 8 litres of Bluecol and took it for a run. I also changed the temp sender, the old one seemed to read higher than the new one but not by much. Gets up to normal quite quickly and sits there, which is how it was before I emptied the system to change the steering rack.

After reading a bit more about the V12 cooling system what I think was happening was water was flowing across the top of the radiator rather than down through it due to it being blocked by the silt. I'm surprised how little silting had caused this. I also read that you should never run the car without thermostats. When the thermostat opens it blocks a bypass pipe forcing the water through the rad rather than just around the engine.

Anyway, fingers crossed its going to be ok now.

Thank you for all the comments.

[helge.kassel]

Hello from Seville,
due to light problems with the temperature in this hot clima and having read the article, i looked in my SIII, whay happened to the thermostats.
To my surprise there was nothing in the places.
Fortunately i had ordered some weeks ago a pair of high-flow thermostats from Rockauto in the USA. After making new seals i could mount them.
I ask myself, how much V12,s are working without thermostats.
What is clear, if you are interested in "How it Works", You will understand, why the cooling is better with thermostats .
Thanks to the pacience of some senior members and studying the workshopmanual on CD, everyday i learn a bit.
Helge Kassel

[Heuer]

The thermostats also provide back pressure on the water pump by restricting flow. With no thermostats you can get cavitation in the pump which erodes the impeller and the housing. Happened on my S1 4.2 after the previous owner ran the engine for years without the stat - pump was in a terrible state.

[politeperson]

Water Pump.jpg (67.5 KiB) Viewed 7440 times

I had a similar issues on my 4.2.

The old coolant that came out was clear blue, however the car had sat for 20 years.

I back-flushed the block with the rad removed.

As a matter of course, I replaced the radiator, thermostat, clips heater matrix, otter switch, fans, pipes . caps, everything.

I has even added a Rob Beere bleed screw.

Therefore I was disappointed when the temperature gauge shot into the red at idle.

No leaks at all.

I got an experienced local mechanic around, who felt the top and bottom hoses when the thermostat was open.

Top was hot but the bottom hose was was cold.

He diagnosed lack of water circulation.

I took off the water pump and guess what. I had no impeller. It had corroded and shattered, I removed large pieces of it with a magnet from the block.

New pump fitted and all is now perfect.

[42south]

hi all you S3 guys,
Just a note of interest if your overheating problems persist.
Our poster Marek has done extensive research on the inadequate length of the modern replacement thermostats. He has posted pictures and results in his photo album over on the Jag Lovers website,(I think).
Basically some, read most of the modern replacements, do not open enough when hot, to close off the bypass.
Fixes could involve a spacer brazed to the bottom of the thermostat blanking plate, or a fitting in the housing to increase the height of the hole to the bypass.
When rebuilding, I took my housing to the machinist and had them mill a couple of mm off the top of the housing and the internal lip.
Cheers
Mark

[MarekH]

You can find my posts on this topic on jag-lovers.org - I used a couple of top hats made of delrin under the thermostats in my v12.

Not having an impellor is pretty bad news - you have no water flow and are operating as an air cooled engine without all of the extra cooling fins that are part of such a design! The next worst thing is the amount of silt and crud in the cooling system. At the engine end, this is stopping (and insulating) the water from getting to the hottest parts and at the radiator, this is restricting efficient waterflow. On the air side, make sure that the airflow is through the radiator, not around it and make sure the radiator fins are clear of debris.

You can generally improve your cooling system design by removing as many of the rustable items in the water path as you can by replacing them with other materials like brass.

Contrary to what you might think, having a lower rated thermostat doesn't really help much - it will simply let you know you are doomed "several degrees earlier" than the higher rated thermostat. Hopefully the extra few degrees of headroom before the cooling system fails will allow you to take prompt remedial action rather than face a failure.

I have also considered electrical water pumps in this application, but if you look at the theory behind having an electrical water pump, it actually does little for you below about 3500-4000rpm. This is because the resistance to flow of a belt driven water impellor is a function of the rpm cubed (same as the Bugatti Veyron top speed argument) so the horsepower saving (and that's power being used to make cavitation on your impellor) is only significant as the rpm rises at the very top of the range. For example, if you lose 8hp at 5000rpm, then that figure would be 1hp at 2500rpm or 1/8hp at 1250rpm. At any sensible road speed rpms, all the electric pump controller does is mimic and remove some of cycling that the waxstat thermostat does anyway so think of it as an item for racing cars which occasionally have to do low rpm work (i.e. public roads).

kind regards
Marek

[Heuer]

There was a very full discussion on thermostats here: http://www.myetype.co.uk/forum/viewtopi ... 081#p65081 which prompted SNGB to revisit the subject and source and supplyi the correct versions for each model.