4.8 ls in a 1974 mgb
Thread Starter
Launching!
Joined: Aug 2012
Posts: 203
Likes: 2
From: harrisville R.I
4.8 ls in a 1974 mgb Just wondering if someone has had this problem before. Not every time I drive her but often enough to be bothering me, she pushes antifreeze thru the top of cap. Now I have been driving her for 4 years with no issues at all. So when this first happened I put a new cap on and it didn't happen for a while, but then it did it again so I replaced the thermostat and drove the **** out of her and nothing for about 100 miles then it happened again. There is no antifreeze in the oil, it doesn't shoot out with cap off and you start it. and I can not smell any out the exhaust. So any thoughts thanks in advance guys
What type of radiator and cap are you running?
These cooling systems create pressure and the coolant will expand and contract. So it sounds like the coolant is expanding, building up more pressure than your cap can hold so it pukes it out.
The factory combats this with overflow jugs. A small hose goes to a port right under the cap, when the coolant expands it pukes into this jug instead of the ground.
It can also pull coolant from this jug back to the radiator somehow. I still dont understand this, but i was told if the radiator is low it will pull a slight vacuum sucking coolant back in. Ive seen it happen and still dont get.
i figure it works like positrac in a Plymouth, it just does.
These cooling systems create pressure and the coolant will expand and contract. So it sounds like the coolant is expanding, building up more pressure than your cap can hold so it pukes it out.
The factory combats this with overflow jugs. A small hose goes to a port right under the cap, when the coolant expands it pukes into this jug instead of the ground.
It can also pull coolant from this jug back to the radiator somehow. I still dont understand this, but i was told if the radiator is low it will pull a slight vacuum sucking coolant back in. Ive seen it happen and still dont get.
i figure it works like positrac in a Plymouth, it just does. 
