How much would you expect water level to rise in header tank

[langtoftnick]

Hopefully my last question on the subject of cooling systems!

I am fighting with my Bongo and have at last got all the leaks, I hope, installed a themostat (!), fixed the coolant alarm, mastered the bleeding technique and got it so that it has antifreeze/coolant and no (hopefully) air in it.

When you start off with coolant at the correct level in the header tank, and then run it up to temperature such that the fan starts to cut in, how far would you expect the coolant level to rise in the header due to expansion?

When I bled it last night, I ended up with the engine hot and the coolant level in the header brimming the outlet. When I turned off the engine I could see the level receding. A bit of this may be due to residuals coming out of the top of the rad, some due to contraction, some to a reduction in pressure due to the pump stopping.

Today, when cold, it is more or less at the normal "full" level - as far as I can tell as the tank is so stained I can't see through it (dipstick!).

My worry is that when I take it out tonight on its test run the expansion will be such that either it will overflow or will pressurise to the extent of blowing hoses (if the header cap doesn't pop first).

Nick

[Northern Bongolow]

from full line cold, or ambient overnight, to running normal or above to fans on you should see about 10 to 15mm increase in height. any more than that may suggest that the cap is not holding 1,1 bar or the fans are coming on late or there is air in the system that is expanding as it heats.
i tested lots of caps at the bash and replaced 5-6 that were blowing under the rated 1,1.

[haydn callow]

Hopefully my last question on the subject of cooling systems!

I am fighting with my Bongo and have at last got all the leaks, I hope, installed a themostat (!), fixed the coolant alarm, mastered the bleeding technique and got it so that it has antifreeze/coolant and no (hopefully) air in it.

When you start off with coolant at the correct level in the header tank, and then run it up to temperature such that the fan starts to cut in, how far would you expect the coolant level to rise in the header due to expansion?

When I bled it last night, I ended up with the engine hot and the coolant level in the header brimming the outlet. When I turned off the engine I could see the level receding. A bit of this may be due to residuals coming out of the top of the rad, some due to contraction, some to a reduction in pressure due to the pump stopping.

Today, when cold, it is more or less at the normal "full" level - as far as I can tell as the tank is so stained I can't see through it (dipstick!).

My worry is that when I take it out tonight on its test run the expansion will be such that either it will overflow or will pressurise to the extent of blowing hoses (if the header cap doesn't pop first).

Nick

When you had it brimming over hot.....was the cap on the tank???? If it wasn't on, that's why it brimmed.

[langtoftnick]

No the cap wasn't on, I was in the process of bleeding so I needed to keep topping up. I expected it to brim over, I was just surprised at the rate it receded once I stopped the engine.

However, good news, I hope, is that I drove it 30 miles last night with no problems. And this morning the water level still appears to be about right.

I have, however, ordered one of Mr Haydns temperature alarm/watch dog jobbies as I don't trust anything under the cover with water in it any more!