Oil and Water                                                                                                             
 

If I had a pound for every time I was asked one of the following two questions by an S7 owner I could retire to Barbados.

Both these problems are simple to fix once the cause is properly understood, they both result from the change in the system installed in the donor vehicle. If you are experiencing either of these problems then read on.

Radiator water loss and overheating

Two problems seem to afflict the RH7; loss of coolant and insufficient cooling with the radiator supplied fitted in the recommended position. The loss of coolant results from the fact that the cooling system in the Sierra donor uses a pressurised header tank and the S7 cooling system doesn’t. The original tank allows for coolant expansion and contraction and is connected to a ‘blind’ radiator with no pressurised cap. The expansion tank is mounted above the radiator and allows the coolant to expand and contract without loss; it simply shunts into the tank and returns as the system cools.

 



The radiator as fitted to the S7 however uses a pressurised cap that allows excess coolant volume to discharge when the engine is hot, this vents via the over-flow. Then when the engine cools, air is drawn in and replaces the coolant lost. This leads to a gradual loss of coolant that can only be corrected by top-up. I have seen some owners try to run a pressurised header tank from the radiator overflow. This is rarely successful as the return from the header tank is connected to the main pressurised part of the cooling system which in turn pressurises the overflow pipe from the radiator, it is not designed to take this sort of pressure and vents coolant.

Many owners seem unaware that the cooling system is designed to vent coolant, the cap valve is two-way and allows re-entry of coolant/air as the system contracts. The trick is to contain the venting and allow the coolant to return to the radiator as the engine cools. The ideal solution to this problem is the system used on the old Cortina.

The overflow pipe from the radiator is connected to a small overflow tank, excess coolant is vented to here, with the vent pipe always below the water level in the header tank so that when the engine cools down and the coolant contracts, water is drawn back into the system. This gives a self contained and maintained system that can be topped up without disturbing the radiator. Ensure however that the radiator cap is the type that has a rubber seal inside the top lip, and that the overflow hose is properly attached to the radiator overflow pipe with a jubilee clip.

If you have this problem get yourself down to the scrapyard and obtain an old Cortina over-flow tank. Bung it in the washing machine to clean it and fit it slightly higher than the level of the radiator, then connect the overflow hose to the radiator and route it into the new tank, fill the tank half full with water – problem solved for good!

Radiator position

On some models of S7, the radiator when fitted in the recommended position is heavily shrouded, front suspension and other gubbins is sited between the hole in the nosecone where air enters and the surface of the radiator. Those cars with inboard suspension are worst in this respect. People who do not fit their nosecone in-fill panels seriously affect the efficiency of the cooling, air enters the nose-cone end then exits through the point of least resistance, namely the side gaps, the result of this is poor cooling.

The thing which most dramatically improves the cooling is to mount the radiator inside the nosecone, it will normally need to be mounted at around 60 to 70 degrees to the horizontal (nearly vertical but not quite). Some simple brackets can be made up to bolt to the radiator flanges and the front cross-member.




A standard Sierra top hose can be used, and a standard bottom hose, cut and extended with some piping can be used on the bottom section. If the radiator is ducted to the nosecone with thin ally sheet in such a way that the air can only go through the radiator, this will improve cooling two-fold.

Another mistake is to block areas of the nosecone aperture with numberplates, hefty grilles etc. This seriously reduces the volume of air entering the nosecone. Obviously the radiator will need an electric fan of some kind as it is now too far away from the engines fan (which can now be removed). The fan should be mounted to push air through the radiator, with the blades no further than 10mm away from the radiator fins. If you have a thermostatically controlled fan, so much the better, if not a switch and a quick eye on the instruments are all that is needed. My thermostatically controlled fan rarely comes on. Most scrapyards will have cars with electric fans from which you can pilfer what is required.

Crankcase Ventilation (AKA my engine pees out oil)

Most engine installations (including the Cortina and Sierra) cope with crankcase fumes by positive ventilation, the way this works is that the crankcase breather on the side of the block is connected via a flame-trap/one way valve to the inlet manifold. The depression in the inlet manifold, draws excess fumes from the crankcase and air is circulated down through the filler cap (which is vented!) down through the crankcase and thereby to the inlet manifold. This ensures that crankcase fumes and condensation are dealt with by being burnt in the engine.

However when Webers or similar are fitted there is nowhere to conveniently mount the ventilation pipe and it is often simply connected to a container, this results is a serious problem since the crankcase is no longer being evacuated by the depression in the inlet manifold. Crankcase pressure builds up because the one way valve does not open until around 5PSI is reached. The resulting fumes and oil are spewed out wherever the point of least resistance is felt; this is now the filler cap which is vented through to the outside world resulting in an oil covered engine. A baffle under the filler cap helps this as it cuts down on the oil splashing around, however the real problem is the build up of pressure in the crankcase. It is possible to block the cap by filling the bottom with epoxy or filler, this blocks the vent to the outside world but just shifts the problem elsewhere, often causing oil seals to weep.




One very effective solution to this problem is to use the crankcase breather from an older Cortina/Capri, which is a large oblong device with an oil separator/drain. The original spout and valve from the engine should be used after first removing the spring and plunger; this is connected to some hose, which is brought up as high as possible (this prevents oil siphoning out when cornering). The hose is connected to a collector tank (which could be any cylindrical container).

 

 

The ideal container allows fumes in, filters them of all oil and condensation and then allows filtered air to escape. The filler cap is then blocked to ensure that no oil or fumes can escape. The fumes can be filtered using ordinary high-density foam such as that used to make kitchen sponges. An additional breather can be used on the rocker box if it is already fitted, the hose from this should connect up to the one from the crankcase and then to the catch tank. Do ensure that any spout leading from the rocker box is properly baffled or oil will be chucked out. The filtered air from the catch tank can either be simply allowed out into the engine bay, or ducted under the car out of harms way.

Dave