The Rover V8 cooling system is a simple one however is often put to blame for overheating engines and much more. It is not uncommon to see such comment online as to “The only way to bleeding the cooling system it to drive the front of the car up on ramps.” Or “I installed manual air bleed valves on this and that hose”. But when you break it down its very simple and as long as its plumbed correctly and has a good to perfect condition radiator with adequate air flow it will have no problem as is with any engine.
The core coolant flow – Block and heads and the basics of inlet manifolds
The engine block itself has a very simple coolant flow. Coolant enters the block on both banks from the water pump that is mounted on the timing cover. Each bank then flows coolant towards the back of the engine. There is a small bleed hole at the front of the block on both banks to allow any trapped air to move up into the front of the head. Increasing the size of these holes should never be done as it will reduce the flow through the block and heads.
From each side at the back of the block coolant enters the rear of each head, it then travels forwards through the heads. Although the heads are ambidextrous (thank god for spell checkers) the water ways that point to the inlet manifold at the rear of the engine are blanked off by the inlet manifold meaning the coolant has to travel forwards through the head.
And that’s it, coolant has passed through the block and both heads, simple.
From there coolant travels into the inlet manifold at the front from both cylinder heads. This is where things deviate depending on what inlet manifold you have fitted but below is the simple break down before going into specifics.
All inlet manifolds of course have the main thermostat housing or main outlet. In addition to this most have a thermostat bypass pipe which continuously returns to the water pump via the back of the timing cove. Some later models have the bypass return to the bottom hose. P38 Range Rovers, Both Lucas Sagem and Bosch Motronic, differ slightly here which I will detail in the engine type specific section.
Then there is a heater matrix feed from the inlet manifold, again this flows at all times (with exception of the MG B GT which has a flow valve attached to it) and then the heater matrix returns to the bottom hose. Often the heater matrix return is T’ed into the main header tank outlet.
On most inlet manifolds there is also a small bleed pipe. This generally flows to the top of the header tank or in some cases to the top of the radiator which would then have a second small pipe at the top of the radiator which would then return to the top of the header tank. This essentially allows any air trapped at the top of the inlet and / or radiator to return to the top of the header tank unrestricted.
Carburetted inlet manifolds
There are several inlet manifolds for the use of carb’s on the Rover V8 engine. The most common are either the original inlet for the use of twin SU or Stromberg carbs, the Edelbrock performer or the Offenhauser intake.
The original intake which uses twin carbs has a tower in the centre (its got a name but it escapes me as I type this and the original MG B GT V8 does not have this). Coolant flows up through this tower and it the highest point on the engine with coolant in it, a great place for the air to collect and escape via the small water port that is located at the top. This would then be plumed, as stated before, to the top of the radiator or header tank. There is also a water outlet on the rear of the inlet manifold that supplies water to the heater matrix and a thermostat bypass pipe on the front of the manifold that both flow coolant freely continuously. Obviously the last part of the puzzle is the thermostat housing, named so because of a wax melt thermostat that locates there and allows water to flow through to the radiator top hose at a given temperature.
The Aftermarket intakes (Edelbrock and Offenhauser) for 4 barrel carbs follow the same platform as the twin carb intakes mentioned above. Both have the heater matrix supply on the rear and a thermostat bypass pipe on the front along with the thermostat housing. They differ slightly though in that they do not have an air bleed pipe, although I dear say one could be added however in my years of working with this type of inlet manifold there has never been a need to do so.
EFi intake manifolds for engines with distributors
Flapper and hotwire (both early and later intermediate serpentine manifolds) although the later serpentine differs slightly as detailed below. Again these manifolds have a small bleed pipe which either plumbs to the top of the radiator or into the top of the header tank. A thermostat housing with a wax melt thermostat and the thermostat bypass as well. One difference to the carb manifolds is that the heater matrix supply on the EFi manifolds does not always come from the rear. The hotwire EFi manifolds (pre serpentine) there is another outlet on the front in addition to the thermostat bypass (still piped to the rear of the timing cover) which is then piped to the heater matrix (often through a long metal pipe that run along the top of the rocker cover which is paired with a second pipe which is the matrix return). The intermediate serpentine manifold differs as its heater matrix supply comes out of the side of the inlet manifold and its thermostat bypass pipe is plumbed directly to the bottom hose seeing as the timing cover and water pump layout is different.
Lucas Sagem EFi (Gems)
Coming soon
Bosch Motronic EFi (Thor)
Comming soon (ish)
So as you can see assuming that the cooling system is fully functional there is no need to raise the front wheels to get the system to bleed like that Facebook post told you too and there should be no need to adapt away from the normal flow of coolant etc. Obviously there are always going to be exceptions such as running without a heater matrix (simple just make sure you still have some flow whilst the thermostat is closed) and of course electric water pumps where the original mechanical pump is removed and if used with controllers mean no thermostat is required, but thats a deviation for another page should it be a point people would like my thoughts on.