Engine coolant routing.

[barkster1971]

I've put in an 80 degree thermostat. However the pipe from the top of the head to the radiator gets hot. Surely that would be a better place for a thermostat?
On a redblock you have the thermostat at the top which prevents coolant going to the radiator until warmed up.
On the D24 it is immediately going through the rad and the fan is spinning. Surely this isn't great as I want the car to warm up fast as possible?
I am going to put in an electric fan anyway but the thermostat only opens once the cooled coolant passes through the rad and along the long pipe back to the block.
i am going to put a better oil cooler in to. Could the pipes be then joined to allow coolant from the back of the head to circulate better?
What are peoples thoughts?

[ngoma]

Originally Posted by barkster1971

...the thermostat only opens once the cooled coolant passes through the rad and along the long pipe back to the block.
What are peoples thoughts?

I think you are forgetting the thermostat blockoff disc, when cold, allows coolant recirculation thru the engine at the same time the main thermostat port is closed, blocking coolant circulation thru the radiator. This helps avoid localized hot spots in the engine as it warms up, as well as providing warm coolant to the heater core more quickly. Eventually the rising temperature of the engine-only recirculating coolant opens the tstat, circulating coolant thru the radiator, and blocking the engine-only recirculation.

So there should not be (much) coolant circulating thru the radiator until the tstat opens.

Are you experiencing overheat problems?

[barkster1971]

Where's the thermostat block off disc then?

[ngoma]

It's pretty hard to miss, lol.

Pencil is pointing to it.



If your thermostat is lacking the blockoff disc, DO NOT USE IT. It will never be able to block the engine-only recirc. port and therefore cannot divert full coolant flow thru the radiator when the engine most needs it (hot).

[v8volvo]

Originally Posted by barkster1971

I've put in an 80 degree thermostat. However the pipe from the top of the head to the radiator gets hot. Surely that would be a better place for a thermostat?
On a redblock you have the thermostat at the top which prevents coolant going to the radiator until warmed up.
On the D24 it is immediately going through the rad and the fan is spinning. Surely this isn't great as I want the car to warm up fast as possible?
I am going to put in an electric fan anyway but the thermostat only opens once the cooled coolant passes through the rad and along the long pipe back to the block.
i am going to put a better oil cooler in to. Could the pipes be then joined to allow coolant from the back of the head to circulate better?
What are peoples thoughts?

The upper radiator hose will get hot at all times with this design, no matter what, simply due to thermal contact with the coolant in the engine. So will the top of the rad, for the same reason. But that doesn't necessarily mean coolant is actually circulating through the radiator. The only time that happens is if the thermostat is open.

The thermostat can work equally well whether it is on the top or the bottom of the engine. Many engines do place the tstat up high in the upper radiator hose outlet, rather than the lower radiator hose inlet. Including the redblock engine like you said. However, it is no accident that the tstat is placed at a low point in the D24T design, and actually in all other VW/Audi engines I have ever encountered also. This is a smart configuration because it means that the thermostat is always submerged in coolant and capable of functioning correctly -- even if the coolant level is low. It also means that the thermostat does not have a tendency to trap air in the system.

With designs that put the thermostat at the engine's highest point, the most serious flaw is that even if the coolant level is only slightly low it can have the effect of interfering with the tstat's operation, fool it into closing when it should be open, and cause the engine to overheat. Getting trapped air out can be challenging too. So to the question of "wouldn't that be a better place for a thermostat" -- I would say the answer is, not necessarily.

Lots of other makers in my experience have also decided on the low tstat location. Subaru, Toyota being well known examples.

All that is to say, it's not a design mistake to have the tstat where it is on this engine. Quite the opposite, it is an intentional decision that has some advantages.

D24T engine warms up pretty quickly, generally not a big concern there. The more serious task for most of them is keeping cool when working at sustained continuous max output on long hills in the summertime.

Circulating coolant from the back of the head is an interesting idea. I have wondered if it could be routed to the radiator. The trick would be to make sure it had some kind of thermostatic control.