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I use very little oil between oil changes (1/2 a litre). So to ensure adequate seal lubrication I add 100cc of two stroke oil to every 40 litres of fuel.

Standard size is 205/60

BenRX, I think you have misunderstood the graph included in the data sheet from bumpstart. The graph clearly shows very little rise in temperature for the water cooled turbo on shutdown, compared with a significant rise in temperature for a NON water cooled turbo. Hence (from Mazda test results) there is no need for (or benefit from) the turbo timer with the Mazda water cooled turbo system.

Like you I rebuilt my engine last year due to coolant issues. The most obvious change since then is that when the engine is started from cold now the top hose remain soft unpressurised and easy to squeeze.
Before the rebuild there was obviously a slight leak in the coolant system allowing the pressure to build up almost as soon as the engine was started. The pressure did not  build up to such a level as to blow any significant amount of coolant out of the system, but often when checking the coolant there had been a very small transfer of fluid into the overflow bottle. On rare occasions on long  journeys , sufficient coolant was blown into the overflow bottle to cause the coolant level buzzer to sound. All that was then necessary was to stop release the pressure from the system and then transfer the coolant back into the system. This happened about four times in a year.
I therefore think that checking for pressure in the top hose is a very good indication of the effectiveness of the engine seals.
Under normal cold start conditions the coolant temperature will rise as the engine warms up. When approximately 83C is reached the thermostat will open and the coolant will pass to the radiator and return cooled to the engine maintaining a reasonable operating temperature. The top hose should still remain unpressurised and easy to squeeze by hand.
The top hose should only become pressurised once the atmospheric boilng temperature of the coolant is reached. Now normal antifreeze will raise the boiling point of the coolant to about 106C dependant on antifreeze ratio. On a fast run or when the coolant system is inadequate then this temperature could be exceeded. Under these circumstances the pressure in the system will be raised as the coolant tries to  boil, this pressure is limited by the radiator pressure cap. This increased pressure further raises the boiling point up to about 125-130C (dependant on the radiator cap setting and coolant mixture). Thus the top hose should remain unpressurised untill the coolant temperature reaches about 106C, at this point it will start to increase in pressure untill about 130C at which point the radiator cap will open to release the pressure and allow the coolant to pass into the overflow tank.
 
If the seals are leaking this pressurisation will occur at normal running temperatures due to just a tiny leak of high pressure gas from the combustion process entering the coolant system and the top hose will be hard to squeeze. So if your coolant temperature is below 106c and the top hose is hard to squeeze then this does suggest an engine seal leak.

I used it on my TII last year when the water seals showed signs of failing, lasted about one month before the seals failed. On strip down there were deposits from the copper like content of the K-seal all around the water ways but none in the seal area. It may be that if the seals have failed in a low pressure area near the intake or the problem is an external coolant leak, then the K-seal may work, but if the seal failure is in a high pressure area as mine was, then it is less likely to work. It\'s very temping to use as it\'s so much simpler and cheaper than an engine rebuild and this thread will help to indicate the possible likelyhood of it working. In my view if your cooling system is not being pressurised by the combustion gasses then it\'s worth a go, but if your getting pressure in the cooling system in my experiance it does not work.
Was your system being pressurised Brett?
The top hose should remain just as easy to squeeze with your hand with the engine running as before it starts, if it\'s not then potentially your seals are failing. This is probably the quickest test for possible seal failure with combustion gasses pressurising the cooling system and hence whether the K-seal has a chance of working.
Just my view and it will be interesting to hear the experience of others.

I tried K seal in my engine when I had an intermittent minor seal leak causing just a small amount of coolant to leak out into the expansion tank every once in a while. It failed to cure the problem and eventually the water seals failed requiring an engine rebuild. When I stripped the engine down I found copper deposits from the K seal throughout the water ways indicating that it had circulated well, but none in the water seal groves so it had not got through to the critical area.
I pay £147 for my insurance, but I\'m no spring chicken.
John

When you eventually have the time, I would like the injectors.

Thanks Prof. You are correct they are not coolant passages, but do indeed run up to the inlet manifold lower ports. I still have the air pump, but they are still not used as the exhaust manifold has no matching ports and simply blanks them off. I will not bother plugging them now as if there is a slight leak it will will not pressurise the coolant system , which was my concern. Thanks again.

I am currently rebuilding my TII engine following the failure of the water seals. Just below the exhaust ports on the rotor housings are two small holes leading into the water jacket. The exhaust gasket and manifold blanks off these holes on my engine and I assume this is standard for UK turbo engines, where these ports are not used. As an extra precausion against possible leakage of the exhaust gasses into these ports I am intending to tap the ports 1/4" NPT and seal them with taper pluges set just below the joint face. Can anyone think of any problem with this idea?

Thanks for the reply. I will try again tomorow night after the penetrating oil has had a chance to work.

After just one years running my coolant seals have failed. I have pulled the motor out and started stripping it down, but am having a problem undoing the eccentric shaft lock bolt. I have tried a long tube through the spanner to give more leverage, together with penatrating oil, but it has not moved yet. Can anyone confirm that this is a conventional right hand thread? Is this a typical problem? I have had problems with some of the other bolts but they all moved in the end with just penetrating oil and brute force.
Having removed the water pump I am amazed at the condition of the water ways, they look new, but I am more used to much older cars, is this typical of the passages around the water pump and front housing?
Regards John

The factory workshop manual provides full details and this can be downloaded from the internet if you do not have a copy.

Over the last 2300 miles I have averaged 22mpg. This is in my 1989 TurboII cab. No town driving and a gentle right foot (most of the time).

I am new to RX7\'s so stand to be corrected, but I don\'t think the seats come from a T2 UK Cab as your front seats have the adjustable lumber support that my UK cab does not have and obviously there are no rear seats in the Cab.
Could it be that your car as a late series 4 was fitted with the optional series 5 leather interior in an attempt to sell of the remaining stock of series 4 cars?
John

The modern HFC equivalent to the old CFC R12 is R134a. In auto air conditioning the old mineral oil lubricant is normally replaced with a PAG synthetic.
I bought a Turbo 2 convertable earlier this year. The body was sound, but there were some problems that needed sorting to get it running well and through the MOT. It also needed a new soft top which I bought from the USA. They are great to drive, even at modest speeds down country lanes, especially with the top down in sunny weather.
Best of luck ,John