Header Tank

[Andymoltu]

Re plumbed the header tank. After a bit of thought had a boss put into the lower near side of the rad. Put a breather/return into the top hose. Unlike the previous plumbing which, like most have the lower part of the plumbing going into the bypass hose and the air bleed using the existing one on the offside of the rad. The impact for many of the header conversions they blow fluid into the bottom of the header and suck the air into the circulation from the top of the header tank. By having the air bleeder at the top and the bottom of the tank on the same side of the pump stops the air being drawn into the coolant circulation.

Looking at the commercial options only then EJ Ward one has the top and bottom feed on the same side of the pump. However theirs has both pipes connected to the top hose which doesn't make great use of the reservoir. The others like the Stagweber connect to the bipass hose and the radiator bleeder. Again the bottom of the header receives more pressure than the top so draws air into the circulation.

The shiny commercial headers lack the translucent properties of the Ebay Mercedes tank which also has a low water level switch. Will wire that in tomorrow 

so far so good.

[V Mad]

Quoted from Andymoltu-

 The others like the Stagweber connect to the bipass hose and the radiator bleeder. Again the bottom of the header receives more pressure than the top so draws air into the circulation.

Can you explain how you came to that conclusion (pressure) please?

The lower connection to the header is at the intake to the pump, so that would be the lowest pressure.  The top tank connection is at the top of the rad adjacent to the top hose which is at a high pressure point. That is what causes coolant (an any air in the system) to flow into the tank at the top, and out at the bottom. 

[Andymoltu]

My experience was that when the bottom of the header tank was connected into the bypass hose (and the top connection to the rad bleeder) there was sufficient flow to push coolant into the bottom of the header tank and air from the top to be drawn into the rad. This reduced when I moved the upper connection into the top hose rather than the rad bleeder pipe which was connected into the O/S of the ali rad. This put both connections closer in the circulation so the pressure differential was less.

Having had the water pump out 3 times and never got it dry I gave up and had an electric water pump fitted. (I was so cheesed off with the car I couldn’t face taking the damn thing off again and went against my usual habit of doing all work myself) The changes to the plumbing they did, along with moving the alternator meant they put the temp sensor in the top hose and  simply connected the top of the header tank back to the rad bleeder. The electric pump seems to generate more flow and by inference the pressure differential between upstream and downstream of the pump greater. (Notionally the system pressure is 20 psi but there are differences upstream and downstream of the pump) Being a clear header you could see the coolant rise in the tank and the air being pushed or sucked back into the rad. It wasn’t just expansion as I connected the overflow into the original expansion vessel (with rad cap removed of course) 

For me the solution was to weld a boss into the near side of the rad, put the upper connection back in the top hose at the highest point. Effectively both connections are close to each other so no pressure differential. (There might be a minimal one cause by the Bernoulli effect but this seems to nil in practice) 

I will try and attach images to make it clearer.

 

Ignore the old overflow as The securing bolt has seized.

[Andymoltu]

Images attached.

Ignore the old expansion bottle - the bolt has seized and needs removal in due course.