JayVee

This morning I took a short drive and after I returned the cooling fans wouldn't shut off. There is some coolant on the garage floor under the front of the engine (not the radiator). The top hose from the radiator to the engine is warm, but the hose from the bottom of the radiator to the engine is cool. Engine temp gauge is reading normal. Any thoughts?


-JV

Will Feather

Sounds like a thermostat to me, but it runs at normal temp?... so maybe not. I had the same symptoms and i changed my t-stat, all is good now.

Another Mass Lister, where you located?

ztnedman1

So if the car is leaking coolant and running hot it maybe the thermostat and not the water pump? Looks like I may change the t-stat in my car and see if that was the problem before tackling the water pump. My leak looked like it was coming from where the water pump is bolted to the block so I assumed it was the pump?

JayVee

The fact that it's running at normal temp is the thing that's got me confused. Maybe it's the coolant temp switch and the leak (it was very small) is a seperate issue. I'm located in Townsend, BTW.

JayVee

It looks like my car's problem is the thermal switch in the radiator. The radiator and engine are now cold, and when I put in the fuses for the fans they still come on full tilt. The small leak is probably just due to a loose clamp. This cold New England weather is brutal on cars.

jtsporsche

besides the tiny leak, whats the problem? engine runs at normal temp so im confused. you say your fans stay on after you shut the car off? so does mine. or do you mean theyre still on the next morning as they NEVER stop?

JayVee

Yes, they were on for way too long (until I pulled both fan fuses). I let the car cool off for a few hours and popped the fuses back in and both fans came on full tilt. After searching the forums I found that this is a common problem due to the thermo fan switch in the radiator failing in a shorted condition, so I just ordered a new one.

Mike C.

Still, keep an eye on that leak. If you don't have history on when the water pump was last replaced or unless you know for sure it is a loose hose clamp... In my experience, if a water pump starts with a small leak it doesn't take very long to become a big leak....

JayVee

I had a couple free hours so I checked out this leak. I dropped the belly pan, removed the fans, and I can now see that the (very small) leak is coming from the seam between the plastic tunnel on one side of the radiator and the aluminum core. This is probably due to the extreme cold temps we had last week. I'm going to keep an eye on it in hopes that the seal expands now that the temps are higher. The thermo switch is definitely shorted internally because I disconnected it and both fans stopped. Now the old Pcar gets to stay in the warm garage for the rest of winter while the new Jeep has to stay in the unheated garage. I'm learning...

S2cab

If the thermostat is stuck closed, the coolant needs to escape somehow. It looks for the path of least resistence. That could be by leaving via the weep hole on a water pump, blowing a hose or heater core. BTW, I have seen cars with stuck thermostats not overheat. Once a coolant flush is done, they overheat because coolant wont go back in 100%.

JayVee

Interesting. That's good info, thanks. On these cars, would the path of least resistance be the outlet hose on the overflow tank?

Mike C.

The coolant won't 'escape' unless something isn't sealing properly. But if you really overheat it from a stuck thermostat then eventually something will give - often the head gasket due to head warpage. If a thermostat is stuck fully closed, the engine will overheat (unless maybe you're in Fairbanks, AK in winter). A leak from the plastic header tank to aluminum core joint on the radiator is a common failure mode for these radiators. It is most likely a crack in the plastic at the base of its flange. These can't be fixed since header tank replacements are not available.

JayVee

Yeah, I'm hoping that whatever tiny gap is there seals itself with a combination of heat and some ancient radiator crud. "One man's sediment is another man's gasket". If not, then I'll pick up a used radiator.

-JV

JayVee

Whoa...I just realized that I should clarify this: The phrase "One man's sediment is another man's gasket" refers to matters of automotive cooling systems and household plumbing only, OK?!!

JayVee

Here's a wrap-up for those of you who were following this thread from a safe distance:

I installed the new thermo fan switch and the fans are working correctly again. As a bonus, I took a nice long test drive yesterday, and today the small leak the car had is gone. This could be due either it's new warm home or the fact that the leak may have been coming from the old thermo switch gasket. I didn't have to drain the coolant to install the switch. After I removed the fan housing (easy job) I just covered the front of the engine with a plastic bag and put a catch pan on the ground, disconnected the negative battery lead, and swapped the switch out. Hardly lost any coolant. (As a side note, I can't imagine being able to fix this car without searching the info available on these internet forums.) On the road again...