Mirror of the Document
written by © Simon (S) Original
05.07.2001 copied with permission from Simons
Head gaskets failure on the K happens for a number of reasons:
NOTICE: At the MGF is a
reasonable difference in the cooling system. The heater [No 11] is at
the MGF controlled with a valve [No 7]. At the Elise is a constant coolant
flow, cause the heater has no valve. Heat for the passenger room is controlled
with air flaps !!
The cooling problem has two sides, water temp and oil temp. What you have to remember here is that the K was designed as a 1.4 for use in low to mid powered FWD cars, the Elise/MGF fly in the face of this in that they are both 1.8 versions with the engine in the rear (OK mid to be pedantic!).
When installed in the typical FWD car (say Rover 200), the radiator is only some 6 inches away from the engine, the sump is sticking out into the airflow under the car, and itís only producing some 90-120Bhp.
From the cooling systems design, the priority was to get the engine up to temp as fast as possible (for emissions/economy etc) thus a closed loop system was created with the stat controlled by the by-pass water. This means that until the stat opens, only the volume of water in the engine jacket and bypass pipe (also the internal heater on most cars), about 3 litres, is circulating, not much water to heat up.
When the stat opens, it does
not have to open very far to get enough cold water to balance the system,
and even when the car is stationary, the whole system just starts to flow
The problem comes when the radiator cct holds vastly more water than the engine (something like 12 litres on the Elise/MGF). All works fine for the std car that just trolls around, spending very little time on full throttle at speeds over 70Mph.
The problems start when the engine is up-rated, driven at 100+ mph, full throttle for 20+ seconds. What happens is that the water back from the radiator gets very cold because of the huge amounts of air forced though it at speed and the relatively slow water flow rate (as the stat [No. 8] is relatively closed).
Now, this is all made worse by the fact that the bottom 2/3rds of the cylinder liners and the rest of the block are cooled by oil. When the engine is in a nice FWD shopping trolley, the oil is cooled by the airflow over the sump, in the Elise there is NO airflow (itís covered by the under-tray). Even with a std un-modified Elise, you can cook the oil on a track in less than 10 minutes, (I have seen oil temps over 160c on std cars!)
Put this all together what you have is the block getting hotter and hotter (and expanding), the head alternating cold/hot (expanding then shrinking) and the head gasket acting like the slip joint between them, thus hey presto Ė blown gasket!
The following just details the mods required to solve the water temp problem, you will still need to do something about cooling the oil.
The solution to this sort of depends on what you use your car for.
Rover Remote Thermostat
The reason for leaving a 2mm hole in the old by-pass is just to ensure that the sender units get a good look at the water exiting the head, Simon found that with his this is unnecessary, but he doesnít use the std wiring anyway.
To do the second, you will need the same type of stat as before, plus a 3 foot length of heater hose and a T adapter to go from radiator pipe to heater hose.
The steps are:
Coolant modification Update from Carl, 13.01.2001
The only problems with doing this mod is that the engine will now take considerably longer to warm up and the sills will be warm all the time.
In order to get a more stable
cooling system on my "F" I made some changes (thanks for initial
idea goes to Simon ). The "holed thermostat" seems to be a good
way to ensure a more steady flow thru the system and also in minimising
the possibillity of a cold shock for the block and head upon opening of
the thermostat. My alteration includes both the holed thermostat AND the
external bypass with a second thermostat close to the radiator.
In this way the start from cold includes the bypass at the holed thermostat and as it starts to open up there is more heat at the second remote one. At around 80 deg. C this one starts to blend thru the radiator and gradualy the system comes to blend any cool water in the system.
Now the chance for any cold water shock on the engine at sudden full throttle is minimised and thermal expansion / retraction will hence be much smaller than before. This is good for the headgasket that acts as a separation between the block and the head. Still of course the best solution would be to get the steel dowels as well as a re-inforced headgasketÖ
My alteration to the cooling
system will be closely monitored at several points with temp. senders
to a logging unit in order to find out the time / temp-scale at different
David Monks, 2006
Such Remote Thermostat gets installed to the Freelander already since 2001
Another image of #8 assembly
and #13 assembly courtesy Dave Livingstone UK
or to my MGF home site www.MGFcar.de
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