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280z Cooling system mystery

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                       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.

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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 by 925280z

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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.

Sent from my N9130 using Classic Zcar Club mobile
 

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

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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 by Kurbycar32

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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.

 

Sent from my N9130 using Classic Zcar Club mobile

 

 

 

 

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6 minutes ago, siteunseen said:

Here's what I mean on twisting the belt.

1487884300202.jpg

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

1487884358133.jpg

 

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

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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 by siteunseen

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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 by 925280z

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36 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.

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.

do you think with proper belt tension this problem would go away motorsport auto claims that there should be 3/4-1 inch of belt deflection

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Fan clutch sounds okay but does it make a louder noise like a constant "whooshing" that stays loud?  They can go bad in the opposite by constantly turning.  They normally make noise at first then quiet down when the oil heats up. 

Try it looser as msa says but I've always ran mine tight.  If you bought it from msa it should be the right belt.

Some smarter guys/girls will jump in soon with other ideas. 

I get tunnel vision too bad. LOL

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also my warm up tens to be a little slower as in once it hits 140-145 i stays there for 2-3 minutes then the temp gauge slowly starts creeping towards 180, then in about 45 seconds it creeps to 225 which is my new operating temperture

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You may have bought a cheap thermostat?  Did it start running hotter with the belt change or did you do all of this at the same time?

Gotta run now but will be reading your thread.  Best of luck finding the problem. 8^)

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4 minutes ago, siteunseen said:

You may have bought a cheap thermostat?  Did it start running hotter with the belt change or did you do all of this at the same time?

Gotta run now but will be reading your thread.  Best of luck finding the problem. 8^)

it was after the belt change when the symptons started

 

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Seems to me that you have the belt too loose or too tight? or the wrong width belt and it's slipping on the water pump pulley.

I know you don't want to but if you have the old belt I'd put it on and see if the problem is still present.  

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Also I would park it somewhere that wouldn't cause any trouble getting coolant, like out in the dirt, no puddles for animals or leave a mess and do like Mr Overlord says in post 3.  On a cool motor with no tight radiator hose from pressure, take the cap off and stick a meat thermometer down in it.  It'll burp up a little but should smooth out after the thermostat opens.  You should see a decent flowing over the top row of cores.

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5 hours 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.

Sent from my N9130 using Classic Zcar Club mobile
 

 

1 hour ago, siteunseen said:

Also I would park it somewhere that wouldn't cause any trouble getting coolant, like out in the dirt, no puddles for animals or leave a mess and do like Mr Overlord says in post 3.  On a cool motor with no tight radiator hose from pressure, take the cap off and stick a meat thermometer down in it.  It'll burp up a little but should smooth out after the thermostat opens.  You should see a decent flowing over the top row of cores.

well do i have some info for you guys haha , when it reached its new operating temperature i saw no coolant flow at the cap just steam ! and not even a lot of steam im talking a little bit more than bare minimum i think were on the right track also my lower radiator hose does show sign of flow but the top takes forever to show signs of flow 

 

 

Edited by 925280z

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It looks like the car started running hot so you replaced the thermostat. Otherwise I would say pull it out and boil it in a pot on the stove and observe it opening. It sounds like this all started before the new thermostat. Maybe boil it anyway just to verify it isn't defective just to rule out a faulty thermostat and troubleshoot from there..

Sent from my N9130 using Classic Zcar Club mobile

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The overheating could be coincidental to the belt swap.  No cause and effect.  Belt and fan problems would show up at idle, like at stop lights, or slow driving.  Radiator problems show up at highway speed.  Thermostats affect both.

The "haha I only saw steam" comment sounds like you don't have any coolant in the system.  You didn't' really explain what you meant.  Are you saying that the radiator is not full?  That could be the whole problem right there.

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2 minutes ago, Zed Head said:

The overheating could be coincidental to the belt swap.  No cause and effect.  Belt and fan problems would show up at idle, like at stop lights, or slow driving.  Radiator problems show up at highway speed.  Thermostats affect both.

The "haha I only saw steam" comment sounds like you don't have any coolant in the system.  You didn't' really explain what you meant.  Are you saying that the radiator is not full?  That could be the whole problem right there.

the full story is that after i did my belt change it started running hotter , i changed the thermostat and no luck , ive been observing the car all day and the symptoms appear as soon as the car gets to operating temperature i thought maybe it was a faulty coolant temp senor ( the one that allows my gauge to work but i got confirmation that it wasnt the case it was marking 240 when i parked my car at my college and the engine was steaming . i tested the fan clutch and it was ok its just weird how it suddenly started running hot , i only drive from my house to my college which is a 10 minute drive on a bad day and by the time im parked the car is at 230-240 . i just observed how my cooling system behaved and the lower hose was showing signs of pressure but the top hose took FOREVER to start showing signs off pressure . im really trying to pin point the problem before i spend a dollar , i really dont want to take it to a shop so they can throw parts at it . id rather find out exactly what it is and fix it in my auto class. 

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You haven't said if it was full of coolant.  And hose pressure is really only a test of the radiator cap.  Pressure comes from heat and expansion, and the pressure is distributed evenly through the whole system.  Didn't say either if you drove 10 minutes on the highway or ten minutes through the traffic lights.  Just making the point that it's the little details that will tell the story.

If you've been hitting 240 and you had a steaming engine, you might have a blown head gasket.  You might never know if it happened before or after the belt change.  But it might be the cause.

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