Hi All Sorry to raise this again but I have observed the following.
I did replace the coolant cap and noted that when the coolant is cold the level in the coolant tank is mid-way on tank seam, which I understand is correct.
However, if I run the engine till the fans come on (engine bay and rad) then observe the coolant tank, the fluid has risen to approx 11/2 to 2 inches within the tank. ). The total level has increased by at least 3/4.
Is this right? or is a sign of something wrong?
Robert
Hi Robert,
Your coolant will expand and the level rise within the system and consequently the header tank when the system heats up and the pressure increases. In my tank the level goes from just above the middle seam of the tank to nearly an inch or so higher. If you get more of a rise than that, I would suspect you still have some air in the system or your system is not holding pressure, allowing the coolant to boil. Make sure that you bleed from all three points. If your coolant level is returning to normal and not dropping when cold, you should not be leaking anything.
I have to put a tiny amount of coolant in mine, maybe about an eggcup full every six months, I put it down to the expansion cap venting.
I do have a system pressure testing kit and even this shows a gradual leak over with the pressure dropping from about 1.5 bar to 1 bar in about 15 to 20 mins. No signs of coolant loss anywhere though.
One thing to remember about expansion caps is that they are quite cheap and nasty, and some maybe have been on shelves for years. For what they cost it may be worth having two or three handy just in case your new spare is not up to scratch.
Finally I did convert a spare expansion tank to test expansion tank caps, with a small pressure transducer built in. They pop pressure at between 1.2 and 1.4 bar.
Pressure testing kits are quite reasonable on e-bay.
Testing a cap
Sundance