"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.

[swedishandgerman]

Two things:

B20 requires the higher pressure cap of the two versions available

If you fill the reservoir to the maximum level when cold, there is insufficient space to allow for expansion when the engine gets hot. Consequently, the pressure builds up too high and the cap pops to let some off. That process expels some coolant as I think you're experiencing, so normal

You should fill the reservoir to about half way between the min and max marks when cold. The level should go to the maximum mark when hot. The above operation of the cap doesn't allow the level to exceed the max mark. This process will happen regardless of whether you have a B18 or B20 cap fitted, so if you're experiencing what I think you're experiencing, it has nothing to do with the incorrect or faulty cap; it's just doing its job properly

As far as I guess, Volvo changed caps, nothing to do with the B20 having some kind of necessity to run a higher pressure, rather than it coincided. Higher pressure allows the coolant to reach a higher temperature to boil. Any cooling system isn't designed to deal with the gases caused by boiling and will empty its contents if boiling happens, so any measure to prevent boiling is a good thing. Fitting a higher pressure cap to a B18 is possible and a good thing. Fitting a lower pressure cap to a B20 isn't the end of the world, but could potentially boil more easily

My advise would be to experiment with not toppling up after it has squirted as what you have described is normal. That is, unless it is coming out of the vent hole at a considerable rate and emptying a good deal of fluid!

[arcturus]

Are there two bottles as in the 140 series, long neck and short neck?

[Bigbunt]

Of course I immediately topped off when I saw coolant splattered down there but prior to that it was as described; about halfway between min and max when cold... Read last night about the 10lb cap on B20's. Refitted the old cap and all seems fine. What got me was that nothing had changed in many months and all of a sudden the cap squirted just as it got to operating temp on a rather temperate morning... It has to be the cap for whatever reason because there are no leaks elsewhere that I can determine.
All part of the experience! So much fun having this thing on the road. I have to post some pictures but just haven't taken time to figure it out. I should be able to do it from my Flickr account, right?
Thanks all, I appreciate it!

[Derek UK]

Amazons also used 2 different bottles. Short and long neck would mean 2 different length caps. Cap is 10psi on the bottle with a full seal type on the rad. Generic full seal caps are sometimes not very good and won't maintain a total seal.
Ref the 2 types of bottle, I thought that the rad brackets and bottle mouldings were slightly different and had to match for a good fit. Happy to have that disproved if anyone can throw light on it.