Radiator not hot?

[choke artist]

Just bought a 1983 Nissan Datsun 720 yesterday. So far it's great but I had a few questions. Not much of a mechanic but I thought this seemed strange.

 

After driving the truck on a fifteen minute trip, the radiator cap wasn't hot...the engine temp gauge showed the engine being warm and wasn't overheating but the radiator cap and top hose were cool. I've checked it a few times and the lower hose going to the radiator gets hot but the top hose doesn't. On one occasion the top hose was somewhat collapsed like it was trying to suck?

 

Is something wrong or?...thanks. I'll post pics soon because if all is well...this truck is pretty rad. '83 with only 79,000 miles on it and everything's original!

[flatcat19]

Blockage? Faulty thermostat?

 

Easy to test.

Since it's a new to you car, changing the anti-freeze seems priority.

 

Wait---hose collapsed?

Compression test? Leak-down?

 

How does the coolant and oil look?

 

 

Oh---and welcome to Ratsun!

Get an intro thread and some pics before the natives get restless.

[metalmonkey47]

Maybe faulty thermostat and temp gauge reading incorrectly?

 

Is the lower hose hotter then the upper? How about the lines to the heater core?

[datzenmike]

15 minutes isn't long enough to thoroughly warm it up. If the heater was on this would also shed a lot of heat. The gauge should read about 1/2 way up in the 'NORMAL' area or a needle width below. If barely reaching the NORMAL range then the thermostat may be faulty/stuck/wrong range. If low after a half hour of driving replace with a new one of 185 - 190F. Don't waste your time testing it.

[Tristin]

For about $7 you cant beat just using a new thermostate. Let me tell you, it fixed a lot of my running issues. My heater works like a champ now.

[choke artist]

Drove to work this morning and it started to over heat just slightly. The lower hose it totally hot but the upper hose is barely warm...

[86 720]

If the hose is collapsing it needs more coolant. The water pump creates a vacuum that pulls more coolant in from the overflow. Fill the ovetflow catch can with the proper amount of cooling. May need to do it twice before the proper amount is reached. You can also remove the thermostat and see how it runs temperature wise.

[Jesse C.]

Don't forget that when you install a thermostat to place the little valve thingy on top. I helps bleed air through the system. Also, make sure you are running the right temp thermostat.

[Kisor]

If the hose is collapsing it needs more coolant. The water pump creates a vacuum that pulls more coolant in from the overflow. Fill the ovetflow catch can with the proper amount of cooling. May need to do it twice before the proper amount is reached. You can also remove the thermostat and see how it runs temperature wise.

 

I'll add to this by saying go for a new cap also. If the cap is bad and it can't draw the coolant from the overflow this may be part if the issue.

 

Does it have good heat in the cabin?

 

And after the longer drive was the top hose still collapsed?

[choke artist]

Changed the thermostat and the problem is fixed...it was starting to overheat after a fifteen minute trip.

 

After changing the thermostat and refilling the coolant system, I drove to federal way and back (from tacoma by the bridge) and it was running like a champ.

 

Now to fix the other minors problems...it runs rough when first started up....and since I fixed the thermostat...it's been dripping a bit of oil...