"Random" coolant squirt?

[Bigbunt]

Okay, what am I missing here? I've put about 1k miles on my '67 two door with b20 since going through the whole car (almost!) after a lengthy time off the road. All new coolant hoses, repaired leaking radiator neck and pressure tested radiator, new caps on radiator and overflow bottle and all seemed to be fine. This morning went out for coffee and got a whiff of coolant which came and went but I pulled over for a quick check. Found coolant splashed/squirted all on the right side of engine bay. Hard to determine source. Added less than a quart of coolant and drove home carefully. No overheating. Rinsed whole area with fresh water and let things dry out a little.
A couple of hours later, started it up and let it warm and pressurize and stared intently with a strong light at the whole area and no apparent leak at all. Did notice a little bubbling but no fluid leaking from the small vent hole on the back side of the overflow bottle neck at the pressure cap. One theory I have is that the cap released pressure and belched fluid out the vent? Could that happen and why would it is one question. The next question is what else might do this? Kind of confounds me...

[Groundes-Peace]

From your description it sounds as though you need to change the pressure cap on the expansion tank. As described it is not holding enough pressure.

[Bigbunt]

The cap is brand new plus 1000 miles. That's what confuses me. It was from IPD or one of the specialty suppliers our side of the pond. Is there a pressure amount I should ask for? I might just go for a NAPA or other mass market supplier. It does have a nice Swedish sticker on it though! I'd hate to lose that... Might try the old cap... I was just trying to be thorough.

[Derek UK]

The new cap might be a bit too short, compare it with the old and yes fit the old one and test. Also check that the top of the plastic bottle isn't distorted. I've had one like that and the sealing ring then sat at angle and leaked at very low pressures. Would mean that it would boil and blow out when you came to a halt after a run, or when idling in traffic after coming into town. Lift the bottle up higher than the top of the rad when bleeding, that gets rid of any air in the rad. Half way between the marks is fine when cold, it will then probably show just above the top mark when hot.
A water pump leak can also drip coolant onto the fan belt and fan which then centrifuges it outwards.

[Volvorama]

I think I have come across two different heights for radiator caps. I used to do high mileage in a 131 and that did squirt out coolant from the bottle every so often until a put a higher pressure cap on.

[arcturus]

Quite often the"whiff" of coolant in the cabin comes from a leaky heater matrix or leaky pipe connections. See what happens with the heater turned off.