My problem happened after i replaced my alternator belt, my 77 (technically a 76 because of its production date) used to run at around 180-185F , now the norm is 210-230 or really close to over heating after a 7-11 minute drive and considering the weather in california is fairly cool/cold this problem is really weird to me. I already replaced the thermostat and its gasket (no luck) there are no leaks , other things that ive done to my car during this period where , an hks smf filter (mostly for looks) and replaced some worn rubber hoses that run across my intake manifold (which fixed my bad idle) this car is my daily driver to college please any help is welcome.

The new belt should be tight.  Only able to twist one fourth of the belt. It runs the water pump as well as the alternator.

Perhaps the first thing to do would be to verify the coolant temperature by checking it hot with a meat temperature gauge or something of the sort.

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13 minutes ago, siteunseen said:

The new belt should be tight.  Only able to twist one fourth of the belt. It runs the water pump as well as the alternator.

do you mean that when its off it should be able to rotate 1/4 of a revolution? it has no play at all right now ?

Edited February 23, 20178 yr by 925280z

9 minutes ago, Reptoid Overlords said:

Perhaps the first thing to do would be to verify the coolant temperature by checking it hot with a meat temperature gauge or something of the sort.

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dumb question but how should i do it? pull the cap off when its running ?

Verify your fan clutch works.  I also drilled 2 1/8" holes in my new thermostat when i had a similar problem in my Z.  It allows the warm water to surround the thermostat a bit easier and in my case it started opening correctly.  Its an old hot rodder trick and supposedly not necessary with a good quality thermostat but those seem to be hard to find.  Google it

Edited February 23, 20178 yr by Kurbycar32

Here's what I mean on twisting the belt.

Grab this hub and try to turn it.  You shouldn't be able to budge it.

 

Take the radiator cap off cold, then I would drain just a little bit, enough to prevent any from coming out of the radiator cap hole during warmup, and still enough to get a reading. Then let the car run until it reaches its highest operating temperature. Check the coolant when the dashboard temp gauge says 210-230. Just keep an eye for boilover from the open radiator hole.

 

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6 minutes ago, siteunseen said:

Here's what I mean on twisting the belt.

Grab this hub and try to turn it.  You shouldn't be able to budge it.

 

the hub does not budge but i can barely turn the belt not a full 1/4 maybe half of that

I have a 180 thermostat in mine.  When it gets to that temp it opens and you'll see coolant moving in the radiator.  After mine opens it drops down to 170-175.

8 minutes ago, 925280z said:

the hub does not budge but i can barely turn the belt not a full 1/4 maybe half of that

That new belt may have ruined the water pump?  Hopefully not but I've read where the tightness of the belt ruins the old bearings in the pump.

Checking the fan clutch is a good suggestion.  See how many rounds it'll turn by spinning one blade by hand.  Shouldn't make a complete rotation if it's cool.  It is oil filled and gets looser with heated up oil.

If the bearings are bad in the pump you'll be able to hear something rattling or the blades scraping the inside of the housing.  I shouldn't have mentioned that, sorry.

Edited February 23, 20178 yr by siteunseen

11 minutes ago, siteunseen said:

That new belt may have ruined the water pump?  Hopefully not but I've read where the tightness of the belt ruins the old bearings in the pump.

Checking the fan clutch is a good suggestion.  See how many rounds it'll turn by spinning one blade by hand.  Shouldn't make a complete rotation if it's cool.  It is oil filled and gets looser with heated up oil.

i tested the fan and its semi warm but the max rotaion i could get with a good push of the blade was about 5-7 inches ( not enough to put the next blade in the same spot as the one i pushed ) is there a way to test if the bearing is worn/shot? should i be able to hear the rattling when its running ?

Edited February 23, 20178 yr by 925280z