Triumph TR6
Matt investigates a worrying TR6 development…
As reported previously (Practical
Classics, January 2020), the TR6 enjoyed a 2500-mile run around Europe on the Club Triumph 10 Countries run back in September 2019. During the trip, issues encountered were generally of the niggly kind
– a headlamp unit that made a bid for freedom and a non-functioning heater (my own fault) for example. By the time the car was back home in Cambridgeshire, it had clocked up 5000 miles on the rebuilt engine. I’d had to top up the coolant more often than I liked during that time, but had put the fluid loss down to a leaking hose connection somewhere in the system. Worryingly though, the amounts required each time had been getting bigger and bigger.
However, it wasn’t until after I’d treated the TR to a post-10cr oil and filter change that I finally clocked a build-up of the dreaded emulsion of oil and water or ‘mayo’ on the underside of the rocker cover cap. I cleaned it up and drove home from the PC workshop to my house, which is a distance of about 25 miles, by which point the cap already had a fair covering of mayo on it once more.
When the engine had cooled down, I checked the coolant level in the radiator and found that it had gone down significantly. Uh-oh. Despite the car never overheating and performing quite brilliantly, with the temperature gauge remaining in the middle at all times, there was clearly a significant issue.
Worrying times
My heart sank – after all the work that had gone in to get the ’6 back on the road, this hitch felt like a disaster. I parked the car in my lock-up and there it sat for a good few months, still wearing its event stickers and covered in road grime. I busied myself by repairing the rotten sill and rear wheelarch on my 2000 saloon instead (see boxout on following page), but once that was done, I was ready to sort the TR once and for all.
I picked up a head gasket repair set from TRGB and headed to the workshop to meet Matt Tomkins. When I drained the oil, what came out
‘I drained the oil and what came out was watered down, brown and nasty!’
was unpleasantly watery and had turned a rather latte-esque shade of mid-brown. With the coolant also drained off, we started taking the top end of the engine apart.
Once removed, the rocker cover revealed itself to be hiding a thick coat of mayo, so it was treated to a thorough de-gunking in our trusty parts washer. The rocker shaft came off next, followed by the inlet manifold (complete with carbs) and the exhaust manifold. Once the heater hoses and pipe were disconnected from the block, the time had come to remove the head itself, complete with impellor housing and water pump still firmly attached. Thankfully the head came away easily enough, but Tomkins and I did have to rope in some extra muscular help to get it up and away without dropping it and damaging either ourselves or the car.
What have we got here?
With the head out of the way, the process of investigation could begin. The head gasket didn’t show any obvious signs of damage, but there were a couple of small raised spots, one at each end between cylinders. There were also raised spots on the face of the cylinder block that corresponded with the spots on the gasket – clearly this wasn’t a coincidence. Happily the raised spots on the block were easily removed with careful use of a razor blade, meaning the new gasket could seat properly.
My best guess as to what happened lead me to believe that the head hadn’t been fully torqued down or, more likely, not sufficiently re-torqued down after the initial 500-mile running in period. With the head having shifted ever so slightly, water had found its way out of the water jacket and underneath the gasket, leading to the build up of gunk that caused the high spots to form and allow oil and water to mix.
With a fresh gasket fitted, the head torqued down to the factory figure of 85 lb ft and the valve clearances adjusted, all of the ancilliaries were bolted back on to the engine. With fresh oil and coolant in place, I fired the engine straight up. Once the cooling system had ‘burped’ itself to remove any pockets of air, the six-pot settled down to a happy tickover. I completed my 25-mile journey home and everything seemed fine. Is the problem fixed? I’ll let you know soon.