Cooling system

bigdaddycain · Post by **bigdaddycain** » Wed Mar 26, 2008 1:00 am

That's a lovely bit of billet ally there mel...

dandywarhol · Post by **dandywarhol** » Wed Mar 26, 2008 1:00 am

bigdaddycain wrote:
The Great Pretender wrote:
haydn callow wrote:I suppose one theory could be to remove the stat altogether....live with a slower warm up cycle.....then...if indeed some of the head and gasket failures are caused by the stat open/closeing all the time (I don't go along with this yet) and letting cold coolant rush in causing head/gasket failure, then the removal of the stat would prevent it .
I dont go along with the stat opening at all. Even with it removed water dosnt flow through it.
It must flow through with it removed mel,i was present when pat mckennas bongo had the hoses replaced for flippas hoses,his bongo simply would not bleed up with the stat in situ.

Eventually,the stat was deemed to be fooked,it was temporarily removed, bled instantly with no issues, but took an age to get up to temp... The temp gauge never got past ten o clock though... Bottom hose got hot.

It would take an age to get up to temp cos your man bleeds it with the a/c on and the heater flaps open according to blueozziedave

bigdaddycain · Post by **bigdaddycain** » Wed Mar 26, 2008 1:05 am

dandywarhol wrote:
bigdaddycain wrote:
The Great Pretender wrote: I dont go along with the stat opening at all. Even with it removed water dosnt flow through it.
It must flow through with it removed mel,i was present when pat mckennas bongo had the hoses replaced for flippas hoses,his bongo simply would not bleed up with the stat in situ.

Eventually,the stat was deemed to be fooked,it was temporarily removed, bled instantly with no issues, but took an age to get up to temp... The temp gauge never got past ten o clock though... Bottom hose got hot.
It would take an age to get up to temp cos your man bleeds it with the a/c on and the heater flaps open according to blueozziedave

That's correct dandy,as it should be,with the stat removed pat's bongo took much longer to reach operating temp,as the stat was previously only opening when it reached a constant 100 deg.

Despite running pat's bongo around for half an hour above 3000rpm,the temp gauge never moved beyond 10 o clock.

After checking with pat later, it never moved beyond that point on the run home either,air con off,front heater on position 1,temp control mid blue/red.

The Great Pretender · Post by **The Great Pretender** » Wed Mar 26, 2008 1:06 am

The brass take off feeds a pressure sensor and as it is temp and pressure related it will take time to collate sensible readings, but I have had over 21PSI at less than max temp.

So 30PSI in the system looks possible.

The Great Pretender · Post by **The Great Pretender** » Wed Mar 26, 2008 1:15 am

bigdaddycain wrote:That'
s a lovely bit of billet ally there mel...

Yep aerospace alloy.

bigdaddycain · Post by **bigdaddycain** » Wed Mar 26, 2008 1:19 am

Lovely...you can't beat a spot of extruded billet....

dandywarhol · Post by **dandywarhol** » Wed Mar 26, 2008 1:34 am

How can a system run at 21 psi if the cap blows it's valve at 16 ish psi

The pressure must be felt through the complete system...............

The Great Pretender · Post by **The Great Pretender** » Wed Mar 26, 2008 1:51 am

dandywarhol wrote:How can a system run at 21 psi if the cap blows it's valve at 16 ish psi

The pressure must be felt through the complete system...............

Different part of system, reduce speed increase pressure.

haydn callow · Post by **haydn callow** » Wed Mar 26, 2008 9:49 am

I said eh! co's it was said that with the stat removed water would not flow ??? Don't get that, beyond me.
I thought the pressure in the system was created by the coolant expanding....and compressing the air in the header tank.
Now I am going to have to rethink the whole thing through again. I also thought the water pump "pumped" the coolant round the system..How else would it get to the rear heater "downhill by convection"
This is all very worrying.

dandywarhol · Post by **dandywarhol** » Wed Mar 26, 2008 10:16 am

The Great Pretender wrote:
dandywarhol wrote:How can a system run at 21 psi if the cap blows it's valve at 16 ish psi

The pressure must be felt through the complete system...............
Different part of system, reduce speed increase pressure.

Interesting, keep testing

I understand that water flow/speed affects pressure but I need to get my head around whats happening in a sealed system with the only outlet through a pressure cap (or 2

)

The Great Pretender · Post by **The Great Pretender** » Wed Mar 26, 2008 11:24 pm

Haydn coolant not flowing through the main hose with the stat removed shocked me to. On the standard setup I think the pressure rise will be mainly down to temperature as you found.
The MG article was informative, I wouldn't have put the stat where he did as it puts extra pressure loads into the hoses. It was a shame that he didn't monitor pressure as it would have been very intresting to see the correlation of altitude (climbing the hill) and rising pressure due to increased temp and engine speed.
By putting the stat on the outlet of the head, even when it is fully open it creates a restriction in the system. When the motor is working hard on the head side of the stat the water is moving slowly with the pump and temp building pressure. At around 4000rpm this is about 21psi (would be higher in hot weather). As the coolant passes through the stat it speed increases and the pressure reduces, the rad cap then controls the pressure. That help Dandy?
The theory is that the hottest part of the head is around the exhaust ports, and by increasing the pressure you are raising the boiling point there so there is less chance of localised boiling and gas pockets forming allowing thermal shock.
Im shure that as the head is subject to differing temperature across the ports stress will occur and lead to head failures no matter where the stat is, but by minimising stress it improves the chances of a long life.

Aethelric · Post by **Aethelric** » Wed Mar 26, 2008 11:31 pm

I love this thread
Where can I find the full size picture of the coolant system so I can try to find out what everyone is talking so eloquently about.
Dave

The Great Pretender · Post by **The Great Pretender** » Wed Mar 26, 2008 11:36 pm

Aethelric wrote:I love this thread
Where can I find the full size picture of the coolant system so I can try to find out what everyone is talking so eloquently about.
Dave

http://www.lushprojects.com/bongoparts/pages/

haydn callow · Post by **haydn callow** » Wed Mar 26, 2008 11:36 pm

TGP...interesting...what temp does your stat start to open in the new location ? I am in the proccess of making a new improved in-line stat housing which will have a pressure takeoff and a temp probe within it. I am also first going to fit a underhose probe "temp" in the bottom hose where joins the factory stat housing and try and find out exactly what is going on in there.

The Great Pretender · Post by **The Great Pretender** » Wed Mar 26, 2008 11:47 pm

The stat is 82c Haydn. Im thinking about using extra probes to find out more. Where are you going to fit your stat? Do you know if the origional stat contols a bypass?