Sonymaster20

iTrader: (3)

hey guys I have a 84 z28 i just purchased and am having a problem with it over heating on the freeway, gets up to about 240, which is when the fan kicks in i believe, and begins to cool down to about 230, then on back up.

so far i have replaced the
thermostat,
upper and lower radiator hose,
and radiator cap.

the air dam is there, and there is nothing currently blocking the radiator..

what do you guys think it could be?

Water pump?
fan clutch? it is mechanical, yet is spinning with the motor.

Radiator also doesnt have any mars, scrapes, or scratches to it.
If you could get back to me soon your help would be appreciated as I am trying to get this thing across country..

Thanks

camaronewbie

Is it actually boiling over into the resevoir? If it's not boiling over, it's not overheating. These guages don't read too accurate most days - they are for show mostly.

Sonymaster20

iTrader: (3)

its not boiling over, I am getting a good reading, I used a temp gun with the laser on it and it registers 230-240 when pointed at the block

8t2 z-chev

check that airdam to ensure it is not limber or cracked
and flexing back at speed-my car will often run a little
hotter running at high speed on the interstate on hot
days though not as hot as you are getting-high temps
i seen were around 220-230* i know the cause on mine
is an old,beat up airdam folding under at speed,plan is
to eventually reinforce the original airdam or build a
better replacement one,but this little project is low on
the list as these temps arent much of a bother and an
oil cooler was added later and really helped reduce the
high speed heating tendency.Years ago,one very hot
year and before the oil cooler was added,i swapped
the clutch fan for a flex fan to see what would happen
-reduced high speed temps by 40*in 100*plus
ambient temps-indicating the heating tendency was
airflow related...
There was a noticable HP draw with the flex fan at
over 4500 rpm so the clutch fan was reinstalled.

Sonymaster20

iTrader: (3)

It did seem a little limber and brittle down there to where it could bend under pressure. I ended up renting a uhaul to get it back to houston. When i get it home ill investigate it more. I think it could be the waterpump not oscillating fast enough.

eyner91camaro

Hi. I've got a 91 z28 which I bought back in November. Here in the Northwest we don't get too hot here and when it reaches 75 to 80 degrees I drive my car on the weekends and it's beginning to do the same thing. I've been running my defroster which then turns the AC on running the one fan. Before I knew about this it would get to 240 and turn the passenger side fan on till it got to 220 and turn off. I Would either flush out the system or last resort replace the radiator. I'm gonna replace mine in two weeks. I'll keep you posted. Hope this helps.

henryd3

iTrader: (128)

Try pointing the laser thermometer at the thermostat neck or the upper radiator hose to see the temp of the water coming out of the engine