Another day another potential issue with my 2 owner well maintained '76 XJ6

Since I bought the car around December whenever we have a hot day a little coolant comes out of the overflow hose in the passenger wheel arch. Not something that ever concerned me, my Volvo Amazon does the same on a hot day. Temp gauge always sits happily, never above the L in NORMAL, usually closer to the N.

I have had to top up the expansion tank a few times, which surprised me, as my shitbox rally Daimler has never needed topping up, but then again I've only put about 600km on the Daimler. With the silly black all-metal overflow tank it is very hard to tell where the coolant level should be!

Around a month ago I had a pinhole leak in one of the main hoses so bought new replacements for the big hoses but left the little ones alone for the moment. I had leaks at a couple of the spots where I had fitted the new hoses but a little tightening/adjusting eliminated that over the next week or so.

Yesterday the was a warm day, drove to work and back without issue, stopped for a couple of minutes to pick up my partner and take a short drive and the gauge moved to between the L and 3/4 and wouldn't drop beneath the L. After sitting for half an hour I popped the cap off the expansion and found that there was only a dribble of coolant left in the bottom. Added 2+litres of coolant and water then went for a 10min drive. Temp stayed right down at N, no problems.

Got up this morning to go to work and the expansion was down to less than half full again so added nearly another 2 litres to it to bring it right up to the base of the neck. I have looked all over the engine bay when the engine is running and when it is sitting hot and cannot see any fresh staining/sign of a leak. Car drove happily to work with the gauge reading N again, will check coolant level at lunch. Engine oil looks clean, can't see a leak in the engine bay, no white smoke... Am I missing something obvious with these?

thanks!

 

Pressurize your cooling system with 12psi of pressure when cold and look and listen for a leak. You can pressurize it using a hand pump device that replaces the radiator cap or put a T fitting inline and use shop air. DO NOT excede 25psi. Sometimes a small dripping leak can hide itself when hot becasue the water evaporates quicker with heat. For example a radiator with a pin hole leak at the top will be very dicfficult to see becasue at speed or not the water will be quickly evaporated by air movement.

 

Series 2, the fun NEVER stops, why should it.

Heater tap, #1 cause on all mine. Use the Falcon/Commodore 5/8" universal vac tap, about $20.

The actual heater supply hose off the very rear of the inlet manifold. the one that winds its way thru the throttle linkages is #2 on my list.

The radiator cap. Just coz its new dont mean its right. I took my pressure tester to work a while back, looking for a cap for the XJ-S, and 20 caps later found a 15lb that actually blew off at 15lb. Fair dinkum, quality control is a joke. That cured the intermittent bleeding of green fluid out of the header tank of that car, simple $7 cap, and it only took me 6 months to find it, coz the caps were NEW, so NOT on my radar.

The 2 heater hose on the LH side at the firewall. They can be a mongrel to get the clamps positioned right, and will dribble down behind the insulation panel.

If I think of more I will return.