4.2 litre Series 1 E- Type radiator Cap

I preferred that the header tank run full regardless of whether the engine was hot or cool.

With the expansion tank / bottle that's the way it works, much the same as most Detroit Iron. When the engine cools, the coolant is drawn back into the system.

Without it, when I checked with a cold engine, the coolant level was below the tank internal baffle plate. That left me unsure as to just where the level was.

As far as I can tell, the Otter switch on the 4.2, in front of the header tank, just sits in water, about in the middle of the tank. No special flows or pipes or anything.

P

Hi Pat,
Perhaps my message was not as clear as it should have been. As you know the Otto switch on a 3.8 is on the top of the header tank . The hot water inlet pipe runs does not just dump into the tank but runs past and directly below the switch, close to the top of the tank. There is a hole in this pipe directly below the otto switch and the bulb part of the switch projects into this hole so as long as any coolant is circulating it passes over the bulb.

Put it this way: if you remove the switch, you drain the header tank.

Hi Patrick,
Does the Otto switch on a 4.2 header tank actually stick in the tank or in a hole in the discharge pipe as on my 3.8? On a 3.8 the tank could be half full and the Otto switch would still work as all in coming coolant is passingover it.

Robert: Those of us that have the Otter switch in front of the header tank don't seem to have that luxury of running a quart low. If your tank runs low, the otter switch does not detect the temperature of the water, and will not switch on. But certainly, after filling the header tank with cool water, there will be a bit of discharge when it expands from temperature...from that point on, the level should remain correct.
David, you mentioned the problem being the loss of coolant, but do you not have any over-heating issues? I would advise a 50/50 mix of water and coolant, and add a bottle of "Wetter Water" or that Purple Ice stuff. If you are still experiencing over-heating, I would advise your getting rid of the highly inadeqaute Series 1 fan blade and motor, and putting on a Cool Cat fan.....no issues with air flow through the radiator after that.....assuming your radiator is stil good.

Patrick

Billy, If you hadn't filled the header tank to the top it wouldn't have kicked out that last pint or so of coolant as it warmed up. I run my 3.8 with the header tank about a quart low and have not had to add any coolant in the last several years.
David, As the higher pressure radiator cap only raises the boiling point of the coolant it had nothing to do with your car running "slightly" cooler.

Thanks very much folks for the comments. I took Patrick's advice and mounted a 13 psi. cap and then put about 75 miles on the car to see what happens. Before I started I did check the tightness of the clamps particularly on the heater hoses. For the first time in 14 years of ownership I did not lose any coolant and the car runs slightly cooler.

Tom ÔÇô I would be interested in seeing photos of your setup. My email address is bendemaol.com

Miklos

Edited on 2010-03-16 13:38:57

On our '63 E-Type (Driven Class) Coupe I used to top-up the radiator when cold only to have it overflow as it warmed up. I solved that problem by removing the windscreen washer bottle (and safely storing it) and replacing it with an expansion bottle assembly.

I had intended to attach photos of the arrangement but, upon checking my stored photos, I discovered that I had stored them at 1.3 Mb each for later printing. Too large a file size for this site.

If anyone would like to view them. send me your email address and I'll attach them to a message.

The later 3.8 cars specified a 9 lb cap. When the 4.2's came out, the cap changed to a 7 lb one. Hoses did not change so should not be a problem with a 9 lb cap. I have not seen a 10 lb cap but have seen 11 lb ones available. I did locate some 9 lb NOS Lucas and A/C caps in England and bought them fro my own car. The biggest problem of going with a higher pressure cap is not so much the hoses but whether the hoses will stay in place under pressure. If you look at the design of the heater pipes on the 6 cylinder XKE, you will see that they are just pipes without any flares on the end. If the hose gets a litle loose, it can slip off. Rare to happen but less rare with more pressure than the system was designed to handle. Most all of the other hose fittings elsewhere on the car have flares to keep the hoses in place. Another issue is solving why your car spills any water at all. You should have your cap checked to see if it is in fact holding the specified pressure. The state of the engine running and cooling system condition will also effect how hot the coolant gets and expands.

I changed mine to a 13 to keep the radiator from spilling its guts....no problems with hoses.
Do it.

P