After running the engine for a couple of miles and then switching off, the car would dump a pint or so of coolant from the overflow on the expansion bottle. My immediate recommendation was to buy and fit a new pressure cap for the expansion bottle. This was done, but with no improvement.
So far we have a new thermostat and pressure cap fitted but we hadn’t fixed the problem. Our thoughts turned to the head gasket. Maybe a blowing head gasket had prompted the removal of the thermostat by the previous owner? I was asked to assist with the replacement procedure, a challenge I readily accepted – and set a target of getting the problem fixed in time for Gaydon. Those of you who know me will not be surprised that I keep a spare head gasket at all times (you only need one when the shops are shut anyway!) so this was taken and fitted to the car. Much scraping of head and block faces later, we had a freshly fitted Payen head gasket and a fully inspected head and bores. As the sun was setting we agreed that a test would be undertaken the following day. Much to our annoyance there was no improvement; the car was still boiling over.
I raided my stock of spare expansion bottles and took them to the car. Two of my spare bottles seemed to hold pressure when using the blow-down-the-pipe test. Strangely, when we fitted the newly-bought pressure cap to the three bottles, it would only hold pressure on one of them, so we fitted this unit to the car. The new pressure cap would not hold any pressure at all on the original bottle so we were convinced we had fixed the problem. We hadn’t.
Where was the problem? Suggestions received from the Triumph Dolomite Club on-line forum ranged from cracked head to choked radiator. As we had already checked the head and the radiator had since been flushed we turned our attention to the water pump. The OHV water pump is a very reliable unit – I have never seen a faulty one, but we stripped it down just to see what was happening. The impeller was turning ok so I removed the housing for inspection. I always run a tap through the thermostat elbow and water pump threads to clear out any muck and corrosion so I took the unit, complete with thermostat and pump, home to do this. On Saturday morning I went to visit David Manners / Parts 4 in Oldbury to get the necessary water pump gaskets (A great place for OHV engine parts as they are Spitfire and TR specialists) – I also bought a new thermostat from Tividale Motor Spares to try by substitution. With less than 24 hours until the gates opened at Gaydon we were running out of time and patience.
I took the new thermostat home and decided to compare the two thermostats using the saucepan method. The findings were surprising. The new thermostat was starting to open when the water in the pan reached 83 degrees, the old one was just starting to open as the water began to boil. BINGO! Problem solved. I rushed the parts back to the car, assembled and fitted them all and refilled the cooling system. Despite the cooling system seeming reluctant to build any pressure we had no boiling over. Tentative tests during the remainder of Saturday afternoon seemed to confirm the problem was fixed and the car made it to Gaydon the following morning with no apparent problems and certainly no boiling over.
We had been caught-out by the most annoying of faults – new parts that don’t work as they should. We all know that we shouldn’t omit new parts from our fault-finding procedures but we all do it. The only remaining mystery was why the car was missing the thermostat in the first place. All I can guess is that the system being un-sealed due to the faulty expansion bottle led to boil-over in the past, so the thermostat was removed to combat this. The challenge was to get the car to Gaydon. Cinderella made it to the ball.
Jod Clark