Overheating

[ABCar]

My 73 developed an overheating problem while on the interstate.  I replaced the thermostat and radiator cap without result.  It was running steady 180 for a couple of hours and then in about 10 minutes went up to about 240 and would not go down.

Turning the heat on, no help.   The fan belt seems to be tight and functional and the fan is turning.    I was told maybe a head gasket or fan clutch.  Any other suggestions?  Thanks.

[Dave WM]

I assume you are using the temp gauge in the car. Have you confirmed its accurate?

[ABCar]

Trust me...it was overheating!!!

[S30Driver]

Check to be sure the lower radiator hose is not collapsed.  Radiator plugged & not flowing adequately. 

i assume there are no visible coolant leaks.  Examine the water pump area.

Hopefully it is not the head gasket - white smoke from the exhaust.

[siteunseen]

While the car is off can you spin the fan by hand, more than one complete rotation?  On mine when the fan clutch is good they will spin about half to three fourths a revolution with slight effort of your finger.  If it spins easily, the oil inside the clutch no good.  Cheap and easy to fix, $20.

[Mark Maras]

 If it overheated when you were moving, it has nothing to do with the fan. The fan isn't needed when the car is moving fast enough to push air through the rad. A complete inspection of the cooling system and a compression test would be where I would start. I had this problem years ago and corrected it with a cooling system flush, re-cored the  radiator (3 rows) and added a shroud for good measure. The compression was good. No problems after that.

[Zed Head]

4 hours ago, ABCar said:

My 73 developed an overheating problem while on the interstate.  I replaced the thermostat and radiator cap without result.  It was running steady 180 for a couple of hours and then in about 10 minutes went up to about 240 and would not go down.

Turning the heat on, no help.   The fan belt seems to be tight and functional and the fan is turning.    I was told maybe a head gasket or fan clutch.  Any other suggestions?  Thanks.

If I read this right you're still driving the car even though it constantly "overheats".  Have you verified the temperature?  Maybe it's a bad gauge.

How long have you had the car?  If it's been fine for years then had this problem all of a sudden then a broken/malfunctioning part seems likely.  The current system used to work.  If it's a brand new setup then modifications might be needed.

[S30Driver]

Zed, this is the very nice 73 that sold on BAT last Thursday.   I believe he is the new owner & driving it back from Omaha to somewhere in Michigan.

Hopefully no damage was done when it overheated.

Edited September 12, 2016 by S30Driver
spelling

[Zed Head]

Ouch.  Two hours is about Des Moines, isn't it?  He has a situation.   So, cruising on the freeway and the temperature shoots up?  Not good.  Mine did that once but it was because a heater hose split.  Pretty obvious.  If it went two hours, you'd think the radiator and shrouding and air flow were sufficient.  Check the radiator for a plastic bag or large bird blocking air flow.  Seems more likely that the head gasket is leaking tough, doesn't it?

[S30Driver]

I hope it is not the head gasket.

The overheating is the reason he was looking for a Z mechanic in the  Davenport IA area yesterday.

[ABCar]

To respond to your questions comments.

First, I am not continuing to drive the car.  It is parked in Iowa waiting for my buddy to pick up with a trailer.

No white smoke. Water pump looks dry, as does the rest.  Lower radiator hose good.  By the time I parked it before leaving I did not get a chance to

spin the fan.  The most noteable symptom is that after parked and cool it will show 180 on (stock gauge and system) on the gauge and then after a whil (10-20 min) it will slowly

creep up to just under the red zone at ~240.  Then is stays.  I am hoping just a clogged radiator although there are few miles on it and it looks like new even though the engine is not detailed or clean.

Would a blown head gasket always blow white smoke...There was none.  Thanks for the replies so far.  Coming home to my tech tomorrow afternoon, so we will see. I will post results.

Yes, this is the BaT car.  (btw, it looks just as good as the picts...I think with attending to minor deferred matainence items and a few new bushings here and there that the car will be everything hoped for)

[Zed Head]

I don't think a blown HG always leaks coolant in to the cylinders.  But I think that if it's leaking combustion gases in to the cooling system that's easy to diagnose.

I almost did the same thing you're doing.  I had a 240Z picked out in California and was negotiating with the seller to pick it up.  I was going to fly down and drive it back to Portland.  The seller changed her mind though and I didn't get the chance.

You might just have a bad gauge.  If you're lucky.  Good luck.