Need help troubleshooting a cooling system issue

soap

soap

Forum Member
I am trying to trouble shoot an issue in a 2002 Ford Ranger 2.3L 4 banger. Guy tells me his heat doesn't work and the truck is getting crappy mileage. I assume the thermostat is stuck open so the truck is in closed loop, thus the shitty mileage. A new thermostat is $150 (you read that correctly) because it is a stupid design with the thermostat, housing, bypass and temp sensor all in one, but he gets a new Motorcraft one despite the cost. I replace the thermostat, change the radiator fluid and fire up the truck to let it heat up at idle in the garage. The truck warms up, gauge on dash registers correctly, clutch fan engages and then turns back off, I assume all is well. I top off the fluid (no radiator cap, just an expansion tank) and we go for a 30 minute drive on the freeway. While we are driving the temp starts dropping on the dash and ends up staying below cold (obviously he has no heat at this point). At the end of the 30 minute freeway drive I touch the coolant and it is cold, not warm or mild but cold. No leaks and exhaust is normal not puffing white smoke. Also the only code being thrown is P0125, which is for insufficient coolant temp (duh).

My gut tells me that it is still a stuck open thermostat (I forgot to test the new one before installing it) so I guess he could have got a brand new faulty part. Radiator hoses get hot (verified with IR temp gun) and expansion tank is full. This seems to be a common problem on these trucks if you do a Google search but at the end of every link I click on there is never a resolution posted!!

Things to eliminate......can't be bad water pump because the truck would overheat, not run cold. Can't be bad radiator for the same reason. A bad heater core might explain the lack of heat in the cabin but doesn't explain why the coolant gets ice cold while driving. There isn't another temp sensor on the engine except for a cylinder head temp sensor but I don't see how that would cause the cold fluid.

Am I overlooking something else? Thanks in advance.

--Joe
 
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is the block getting warm?

block should get hot then radiator

block radiator with cardboard to see if temps rise

possible the clutch is gone in fan


I have a coolant Vacuum if you think you have air pocket
 
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moneypit said:
is the block getting warm?

block should get hot then radiator

block radiator with cardboard to see if temps rise

possible the clutch is gone in fan


I have a coolant Vacuum if you think you have air pocket
Click to expand...

Ken,

I didn't take a IR reading on the block, so not sure. Didn't try to block radiator with cardboard, good thought. If the clutch is bad on the fan and it runs all the time the coolant should still heat up....once driving the air across the radiator is more powerful than the radiator fan anyway. Also I can see the clutch turn on and off and the fan turns on and off with it. Thanks for the vacuum offer, I'll let you know. Also, if I have an air pocket, wouldn't the engine want to overheat?

--Joe
 
depends where the air pocket is,

with the engine off try to spin fan if it moves usually the clutch is good

check the temp of block
and try the cardboard


I chased a wont warm up problem that eneded up being timing chain was very worn causing early ignition
 
OK so just let the truck idle for a half hour. Radiator hoses got warm, and the line that T's off the upper to go to the heater core got very warm. The other line off the heater core was still cool.

My Ford parts guy told me that the heater valve commonly fails on those trucks so that might explain why the heater core isn't moving hot fluid through it. This valve is right in front of the lines that go through the firewall.

http://www.amazon.com/Motorcraft-YG...ie=UTF8&qid=1415396718&sr=8-1&keywords=YG+350

--Joe
 
Not sure on those but did you make sure there are no air pockets in the system? Also the fan clutch sounds suspect because if the fan is turning all the time it'll run cold.
 
If I would have saw this I would have brought my evac home and let you use it.
I had an issue like this with my 07 sierra after I replaced a leaking radiator. After many parts I found the radiator was drilled incorrect and water pusimg coolant they the degas vent at the top which fed the tstat hot water all the time holding it open
 
We blocked off the whole front of the truck and took it for a ride after letting it idle for a while. When we got back the radiator and hoses were cooler than when we first left.

I'm confused.

--Joe
 
BigWheelinBubba said:
Not sure on those but did you make sure there are no air pockets in the system? Also the fan clutch sounds suspect because if the fan is turning all the time it'll run cold.
Click to expand...

All I can do is fill the expansion tank and hope for the best, there is no bleeder or radiator cap etc.

--Joe
 
couple questions to make sure nothing crazy was missed, how did the hoses feel pressure-wise?

Usually a blocked cooling component will lead to an overheating issue but I have seen funnier things happen, crud on the pump, no coolant circulation air in the system and the car reads cold but engine is hot to the touch, radiator is cold.

How did the old coolant look? How do the inside of the cooling system components look?
 
Old coolant looked just like the new coolant....greenish yellow. The radiator, engine coolant and hoses all get warm when idling.....when you start driving everything cools off. No cabin heat regardless of any situation. I did not remove the pump so I'm not sure how the impellers looked.

--Joe
 
Test for remnants of combustion on the overflow tank. If your getting a air pocket after a drive cause may be a head gasket
They make a bubbler & die kit. perhaps someone close to you has one..... if not I do @ my shop.
 
Yea, that's the next area to check Id say.

Is the truck losing any coolant?

Can you put a pressure tester on the degas bottle and see if the needle moves (at op temp) when you rev the engine?
 
soap said:
We blocked off the whole front of the truck and took it for a ride after letting it idle for a while. When we got back the radiator and hoses were cooler than when we first left.

I'm confused.

--Joe
Click to expand...

You win the prize. An engine that absorbs heat. Quick - Apply for a patent before you screw this up and fix it.
 
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