I would still go for thermostat, has it ever been changed?
Hello Peter,
I had another go at refilling yesterday using the heater hose that connects from the valve to the water manifold in which the thermostat is screwed, the thermostat was changed about 5 years, 8K miles ago.
After refilling via the hose held up high with a piece of string attached to the bonnet safety catch, and bleeding, using the bleed valve I'd added to the other heater hose that returns to the drain cock and the bottom of the radiator, I was quite surprised that I hadn't lost anywhere near the amount of coolant that I had first thought.
After the radiator had filled from the bottom up, I started the engine and let her warm up, from time to time increasing the revs for about 20 seconds, when the revs dropped I could frequently hear gurgling in the radiator, but I'm sure there's not a blockage as the radiator was rebuilt completely with a new copper core in 2008, In the May issue of "Viva Lancia" and the excellent, but frightening article, "Aluminum Corrosion in engines" by Bill Smith, he writes in "The Root Cause of Failure" Number 8, " Unless you want your precious Radiator surround to look like the Michelin man"; although not in the same context as this article, this is exactly what my radiator looked like before the rebuild, the header tank was all puffed up, one side of where the casing is soldered to the header tank had failed, and the header tank was being forced upwards at an angle away from the radiator core, the forward face of the tank fits at an angle partly under the hood rail, once it couldn't expand forward any further, it pushed the whole radiator backwards, so it was actually coming in contact intermittently with the dynamo pulley, and also caused intermittent contact with the crankshaft pulley retaining bolt, even at best, there is minimal clearance with the Pulley or the bolt, but at first I couldn't figure out what had changed.
The only reason the radiator man and myself could come up with, was that perhaps the radiator pressure cap had stuck and failed to release excess pressure, causing the damage.
The heater radiator had been rebuilt just after coming back from Turin, we were on our way home from the AGM at Gaydon, when the windscreen suddenly steamed up with a strong smell of antifreeze, and the heater casing filled up with coolant, after bypassing the heater circuit, I drove home with Diane catching the antifreeze in my collapsible bucket, from either the right or left heater flap, depending on direction of lean! after removing the heater, (A right pig of a job on a Berlina), we couldn't find the leak, which eventually only manifested itself under pressure, and turned out to be a split in an end plate that was invisible to the eye, but all was revealed when put under pressure, this was then totally rebuilt.
Last year on the way back to my lockup after attending the Kop Hill Climb event, she did something similar and dumped a fair quantity of the coolant, but once again after letting the engine cool down I refilled her, and once again no further problem until this latest event.
I'm now firmly convinced that all of these incidents have their origins in the same source, and I also believe that there is a very small leak of combustion gasses into the water gallery, which over a period of time (getting shorter) manifests itself by dumping the coolant.
She is now booked into David Thomas Garages for David to do a cylinder pressure test, and to see if exhaust gasses can be detected in the coolant, and if so have the head off and try to sort the problem once and for all.
At the time, the temperature gauge wildly fluctuates from off the top of the scale and back down to about 160/170f in a matter of seconds, which also makes me think that Jai is probably correct in local overheating behind the thermostat, while the thermostat was replaced, I think Omicron supplied a pattern part, as that was all that was available.
I've also ordered a new temperature sender (Jaeger 83492) from Omicron as I've never been convinced of it's accuracy, which was confirmed a couple of years ago after purchasing an infrared thermometer from Maplins.
Thanks to others who have offered helpful comments, I can confirm there isn't a core plug at the back of the cylinder head, so bang goes that theory
All in all I left the engine running for an hour and a half with no problems, on the way back to my lockup the temperature gauge did it's off the clock and back to normal trick, but when I stopped to check, everything iwas ok, hence the ordering the new sender.
Brian
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