94 Altima needle goes to H going up hill

[xKnownShadowX]

My girlfriend's car recently got a coolant leak from under the intake manifold which is now replaced, followed by everything else under there. Before this happened she'd be able to go up a hill at 3k and would be fine, but now if you drive it the same the needle start to go up to the H slowly. I searched and searched but nobody seems to care for Altimas? Anyways, anybody have any idea what it can be? I still gotta burp it again since I think it might be an air pocket somewhere, then look to see if it's loosing coolant. Hope nothing needs to be fixed again.

Her moms 97 Altima also does the same thing. I didn't check that car or touch it though but she says it happens on the freeway I think?

Thanks for information in advance.

[xKnownShadowX]

Anybody?