I currently have a 93 tr magna and ever since i got it, it has been loosing coolant (had rusty water in it when i bought it). I could also hear air bubbles in the heater core (heater on) every time I cold started it. I started by replacing the radiator cap as the old one was stuffed, then the waterpump seal leaked so i put a new water pump on it. now it was starting to hold a bit of pressure but there was still coolant leaking from a few hoses so i replaced them and the clamps. It was still loosing coolant, and there were now bubbles in the radiator but only while it was walming up. so i pulled the head off it. there was a slight leak between a coolant port and number 3 cylinder. I found the Manifold gasket was also leaking coolant, Once I had the manifold out and I looked down the back of the block I could see that the 50mm welch plug thats normally hidden by the inlet manifold was leaking. I took the A/C bracket off and the 2 x 28mm plugs behind it were also leaking. So I replaced all the welch plugs in the motor, had the head tested and machined and went to put it back together.
Now the timing chain adjuster had come out too far and I couldn't get it to retract (I now know it has a lock ratchet on it) so I couldn't get the sprocket on the cam. I decided to remove the timing case (this can be done in the car if your unbolt the gearbox mount as well so u can pivot the engine up and down to get some longer bolts and the harmonic balance out.) I was cursing about this, it really wound me up as I wanted the car on the road today, I soon calmed down when I removed the alternator and saw a trail of old coolant rust running down the side of the timing case.
Once I got the timing case off I could see why! There is an coolant opening that is blanked off between the block and timing case that is for the RWD sigma etc waterpump/timingcase, well the Timing case was seriously corroded around this port that does nothing. The timing case has about 1mm of alloy left between the water port and the timing chain gallery and about the same to the outside so there is next to nothing for the gasket to contact. One of the timing case bolt holes was half missing so the bolt head was acting as the coolant seal. I am so glad I found this now and not once I had the motor back together and runnning.
I now have to pull the Timing case off the other TR I have that has a blown motor and hope it's in better condition. (the wreckers are going to get a complete but completely useless engine by the time I run out of good astron parts and need a change over engine lol )