Cooling Issue - Overheating

Hello! I have been browsing the forums to see if others have run into the same issue as me without luck. Turning to the wise internet for some help. Here is what I have going on:

87 ranger with 2.9L auto. I just did a tuneup after i purchased it - plugs, wires, oil change/filter, coolant flush. After i did the coolant flush, its been overheating. i pulled the rad and flushed it both ways till water was clear, so i am confident there isn't a blockage there. I also flushed the block through the t-stat hole until water was clear coming out the lower radiator hose. I also installed a 180* t-stat. It didn't have heat before i did the flush and re-fill - still no heat. I flushed the heater core from the two metal pipes on the firewall till clear, so I don't believe there is a block there either. The hoses from the motor to heater core were also flushed - all clear.

As I am driving, the temp goes up to about the R and M and holds there for a bit. Then after another 10-15 mins the temp steadily climbs all the way to N or slightly above. As i shut it off there is lots of bubbling and gurgling, the over flow tank fills up. Once its cooled (motor off) the water is sucked back into the radiator from the overflow tank.

I am thinking it could be the water pump (and hoping so reading all the head gasket and cracked head threads). There is no smoke from the exhaust at any time when this occurs. Oil looks fine and there is no "snot" under the oil cap. I did notice one of the heater core hoses was very hot while the other was not hot at all, leading me to think there is little coolant flow through the motor. When feeling the upper and lower rad hoses it seems like there is some flow, but its difficult to say.

So what say you? Any ideas? Appreciate the help!

Not sure what the letters R and M and N mean??
I assume you mean NORMAL letters on temp gauge but their positions changed yearly, so not much definition there for anyone without a '87 Ranger.
Stick with 1/4, 1/3, 1/2, 3/4, ect.......thats the same on all temp gauges

Heater core is most likely plugged if both hoses do not get hot, and no heat inside.
Take heater core out of the circuit to test, by pass it
Either use a connector and a couple of clamps to hook hoses together, disconnected from heater core.
Or pick longest hose and route it to other heater hose's location on the engine, so by pass heater core.
See how temp does after that

Heater core on many years was the bypass for water pump, if that pathway got clogged temp would go up.

Could certainly be your water pump needs to be changed but bypassing heater core is FREE,
Both heater hoses should get hot even with minimal flow, and then there would be some heat in the cab.

Ranger normal operating temp is 190-200degF, thats with stock 192-195 Thermostat
And at that temp gauge would show just below 1/2.
If you climb a long grade or pull a heavier load then it should go just above 1/2, thats normal.

1/2 on Ford gauge is about 210degF


The bubbling in overflow tank after shut down means you had air in the system or an air pocket in a head.
When you shut off an engine there is no more coolant circulation or fan to cool the engine, so internal heat spikes up a bit.
If there was an air pocket then coolant will flow in and flash to steam, increasing pressure in the system which pushes open rad cap and pushes out any air at top of radiator first, so bubbles in overflow tank.
Its not "boiling" bubbles, just hot high pressure in the engine system.

After cool down radiator should be FULL to the top, when you open cap there should no NO AIR at all in the radiator, because it sucks in only coolant from BOTTOM of overflow tank
If there is any air then there is a leak in the system somewhere

Ok thanks for the tip. I will give that a try and see if it helps.

Sorry about the letters, my gause has NORM within the bracket with H and C at the top and bottom. That being said, the needle would start after warm up around 1/4 and then rise to 3/4 or higher until I shut it off.



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My understanding is that there can still be blockage in a radiator, even if water runs through clear. One of the other threads I recently read on here recommended (carefully) searching for cool spots on the radiator, indicating blockage.

When you flushed the heater core, did you get good flow through it?

If it was me, I think the first thing I would try would be to take out the new thermostat, run it without, and see if it still overheats. I’ve had ones that came bad right out of the box before. It may not be your problem, but it’s the easiest, cheapest thing to start with.

On a side note, there was another member here that recently did a bunch of similar maintenance, only to find that he developed problems with the water pump afterward. In his case, he developed leaks around the pump housing immediately afterward. My personal theory was that the flush caused a bunch of old crud to break free, thus leading to problems. There are lots of other people here who are better mechanics than I, so hopefully they’ll chime in soon. Good luck to you, sir!

EDIT - Just read RonD’s suggestion after posting. As usual, his recommendation is spot on. Bypassing the core is cheap-to-free and will eliminate that component with a minimum of effort. Good luck!

Thanks! I am going to do the bypass and see if that solves it. If so, a new heatore core is on the way to drop in. I was thinking that with all the flushing I may have broke old "stuff" loose inside and it may have messed up the water pump. It probably wouldn't be a bad idea to drop in a new radiator, who knows how long it's been on this truck.

The core had ok flow, I think it could be better. Hopefully that's the issue, I had no idea that could cause these issues!

I'll keep this updated as I troubleshoot.

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Heater core can have great garden hose flow but still be block.
Just took one, with great flow, out of my 1994, 1 hose cold no heat in cab, the thing weighed 20 POUNDS, completely full of OLD coolant, and it would not drain out even holding it upside down and shaking it

You can check radiator after engine has warmed up
Shut off warm engine
Move fan cowl back out of the way
Run your hand over rad fins
Should be hot across the top and get cooler towards the bottom
Any "cold" spots are blocked tubes, nice even heat is a working radiator

Water pump is driven by the fan belts. Are your belts loose? Could be a circulation problem if the water pump isn't being driven properly. Air in the cooling system would cause it to run hot and even overheat.

Start it up let it get to temp, pull one of the heater hoses off, usually the top one is best as its the easiest to get to. Let the coolant run out of there until it flows pretty steady then put the hose back on and tighten it down. That's how I've had success of getting air out of the cooling system after a radiator hose replacement, or having to open they system for any reason or just from simply changing the coolant and doing a flush.

wildbill23c said:

Water pump is driven by the fan belts. Are your belts loose? Could be a circulation problem if the water pump isn't being driven properly. Air in the cooling system would cause it to run hot and even overheat.

Start it up let it get to temp, pull one of the heater hoses off, usually the top one is best as its the easiest to get to. Let the coolant run out of there until it flows pretty steady then put the hose back on and tighten it down. That's how I've had success of getting air out of the cooling system after a radiator hose replacement, or having to open they system for any reason or just from simply changing the coolant and doing a flush.

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Belts all are tight. I have read about some issues with the fan clutch? Anyway to diagnose a failing clutch?

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Fan is there to cool the radiator when you are not moving, when you are driving the motion of the vehicle pushes air thru radiator much better than a fan can pull it thru.
As you slow down, or stop, then the fan is needed to keep air flow going to cool the radiator.

So failing fan clutch would cause temp gauge to go up when stopped, but gauge would go back down when you were moving again.

After engine is cold open the hood and try to spin the fan, it will move but should be tight.
Start engine and let it run for 30 seconds or so, shut it off
Now spin the fan, should be much looser and spin by pushing it, clutch is unlocked

After radiator is warmed up, radiator heat control fan clutch, shut off engine and spin fan again, should be tight again, the hotter the radiator the tighter it will be, clutch is locking

If fan is still loose then replace fan clutch and double check center of radiator for heat, if center of radiator is cold then fan clutch will be cold as well so unlocked

I completed the heater core bypass. Cleared the hose and looped it from the head to the water pump, still over heated. I did confirm the water pump is working fine, I could feel coolant moving quite well through that hose.

I am thinking the radiator is shot. I started it up and it slowly warmed up, I know the t-stat opened confirmed by feeling the top hose from the motor to rad. I could feel water moving and it was hot once the t-stat opened.

I went for a drive and the needle slowly crept up to about 75-85%. About a 10-15 minute ride. When I got back, there was no burrbling or air escaping, so I know the system is fully bled. I suspect the clogged heater core may have been trapping air.

Pulled the fan shroud off to feel the radiator...top was super hot and the bottom was completely cold - like cold metal (its about 70 here). No way the bottom would be that cold if it had good flow - i would think it would be around 180ish and I know i couldn't hold my hand on it if it was that hot for the amount of time I was able to. I would say at least the bottom half if not more was like this. The side where the pipe exits was pretty hot (bottom right if facing the truck head on), so coolant is not circulating through the entire radiator.

Of note, I pushed the fan both cold and hot. Both times it has some good resistance, so maybe thats on its way out too.

Does my diagnosis sound right? Any recommendations for a place to pick up a rad (auto)? I briefly looked and found them to be about 60-75 bucks which is pretty reasonable.

Thanks!

Radiator is blocked up, good testing

If you have a manual trans don't waste time looking for a manual trans radiator, they will all be for automatics with trans cooler built in, because it can be used on either.
Yes, that is a good price

Fan clutches are suppose to fail LOCKED, a "failsafe" mode, like thermostats are suppose to fail OPEN, but doesn't always happen that way

Yours reads like it has failed LOCKED so should be fine for now, just louder than normal

RonD said:

Radiator is blocked up, good testing

If you have a manual trans don't waste time looking for a manual trans radiator, they will all be for automatics with trans cooler built in, because it can be used on either.
Yes, that is a good price

Fan clutches are suppose to fail LOCKED, a "failsafe" mode, like thermostats are suppose to fail OPEN, but doesn't always happen that way

Yours reads like it has failed LOCKED so should be fine for now, just louder than normal

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Thanks! I have an auto, so i need to source one of those.

The fan doesn't seem to make any extra noise, so i am going to keep an eye on it.

OK.

If temp climbs at idle and drops when moving again, that means fan clutch is past its prime and time to replace it

Yours might be OK, I forgot about lower radiator being cold, fan clutch has a bi-metal spring on the front, it is heated up by the radiator and slowly Locks the fan speed to water pump speed the hotter it gets.
If radiator was not getting hot enough near the fan clutch spring then it would not lock very tight

RonD said:

OK.

If temp climbs at idle and drops when moving again, that means fan clutch is past its prime and time to replace it

Yours might be OK, I forgot about lower radiator being cold, fan clutch has a bi-metal spring on the front, it is heated up by the radiator and slowly Locks the fan speed to water pump speed the hotter it gets.
If radiator was not getting hot enough near the fan clutch spring then it would not lock very tight

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Gotcha, that makes sense. I'll see how the new radiator does and go from there. Picked one up from rockauto with the little discount from this site. I did notice they all specified without a/c. My truck has a/c (doesn't work) and i dont plan on attempting to fix it. Each pipe and piece that i can easily remove I will over time.

New radiator and heater core did the trick. [emoji91] hot heat and running in the bottom third of the gauge (m for those with NORM).

Thanks for all the help folks.

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