By John Zender
Chapman Report - April 1984
A few months after buying my S2 Europa I experienced some overheating problems that arose from my own ignorance of the proper way to flush its cooling system. I was in my infancy of Lotus life, and was unaware of the consequences of having a little air in the system. When the car started overheating everyone told me to bleed the system. I followed the instructions in the manual step by step until I got to the part about opening the tap on the radiator. I couldn't find it! I knew they couldn't mean the one on the bottom, so I decided that the radiator was either assembled upside down at the factory, or it had been cored and reassembled incorrectly. Eventually I overheated the motor enough to warp the head (although I didn't know it at the time).
After overheating on the way to work everyday for a month, I got up the courage to take a torch to my radiator and try to solder a new valve in. The only reason it took so much courage, is that I am much too lazy to take the radiator out first. I used a small brass valve from Ace Hardware. It's the type that goes under the kitchen sink to feed your automatic ice maker ($1.65). Once I got the valve in I quickly bled the system, wiped my hands and hopped in the Lotus for a short drive. That drive turned out to be even shorter than I expected - the car overheated at the top of the hill.
After watching the temperature needle go out of sight on the hot side a couple dozen more times I decided that those teeny weeny air bubbles I always saw rising to the top of the header tank were being caused by a warped head, I ran down to the parts house and got robbed of $35 for a complete 1470cc gasket set (in stock for some strange reason). Flannagen's machine shop in Belmont did the work in 45 minutes for a reasonable $22.50. I put the engine together that same night and it got me all the way to work without overheating, but no further. The problem still wasn't completely solved.
I racked my brain for the next few weeks trying to figure out the problem, until one beautiful spring day a magic genie rose from my petrol tank. She convinced me of the benefits of selling this great example of British engineering, and buying a small Japan oops, started to day dream a little there Anyway, I noticed that the pipes leading to and from the radiator would get very hot when I drove the car, but the radiator itself would only be warm. Looking at the design of the radiator, I figured there must be a baffle in the end tank between the two pipes. It would be needed to prevent water from flowing straight down the tank and to the lower pipe without going through the cooling tubes. (see figure). To shorten a long story, I ended up drilling a 1/2 inch hole in the end of the radiator so I could see the baffle. There was about a 3/16 inch gap between the baffle and the tank. The options were to dismantle the radiator and repair the baffle, or tap the side of the radiator in until it met the baffle. I took the second option since it was quick and cheap. An easy way to tell if your baffle isn't sealing is to pull out the top radiator tap and slide a wire down the hole. If you can slip a 1/8" wire by the baffle, you've got problems. (be extremely careful not to damage the baffle while doing this).
I figured that the side of the radiator had bulged outward from the pressure caused by overheating the motor. The overheating was caused by the warped head, which was caused by overheating, which was caused by air in the system, which was caused by the lack of a bleed valve. The previous owner of my car must have had a technique for removing the air without a bleed valve, but neglected to tell me.
Once I go the baffle fixed there was only one more problem the engine wouldn't warm up! I had to spend eight dollars on a thermostat.