How to: Replace a thermostat on a 1996 4.0L OHV V6.

[koda2000]

Welcome to this forum! Don't replace the thermostat until you check the coolant level.

and check it in the radiator (cold), not just the overflow tank. if the hose between the rad and the tank becomes clogged (happens) or fits too loosely, the overflow will remain full and the rad can be low.

 

[darknite500]

Thanks for the welcome and thanks for simple advice about check the coolant level. Only had to add almost a gallon and a half, and the heat was coming right out of the vents. I'm surprised that the engine didn't over heat with the coolant being that low. Thanks again =)

 

[lobo411]

You need to figure out why the radiator was so low. You might have fixed the heat problem, or maybe the heat problem was just a warning sign of bigger problems. At minimum, keep an eye on the coolant level over the next few weeks to make sure you're not losing it elsewhere.

 

[BrooklynBay]

Connect a cooling system pressure tester to see if there's a leak.

 

[jlrohio]

Connect a cooling system pressure tester to see if there's a leak.

BrooklynBay (or any other members),

Do you know which thermostat is recommended?

Those that are rated for 180 degrees or 195 degrees?

I see both listed when searching Advance Auto for this motors thermostat.

RockAuto lists the 195 as OE but I don't exactly know how reliable that is.

 

[BrooklynBay]

Most of the time you will see a 195* or a 197* listed as OEM so 195* is correct as far as being OEM. They make fail safe thermostats with a built in bypass check ball.

 

[jlrohio]

Most of the time you will see a 195* or a 197* listed as OEM so 195* is correct as far as being OEM. They make fail safe thermostats with a built in bypass check ball.

Thanks. I picked up the FailSafe 197 degrees brand thermostat at AutoZone with the included rubber o ring type gasket. Israel was the country of manufacturing. AutoZone did not carry the Stant brand.

 

[exporerfreak]

sorry to revive this old thread but we just bought 96' ranger with this motor and it appears to have a leak. in the pics where it shows the thermostat in the block/housing it appears to be leaking from below and behind that section. my fear is that it is a cracked manifold and its going to be difficult to replace. Any suggestions or ideas how difficult it is to replace it?

we bought it for a grand thinking we can probably get it fixed and still be in for less than its worth....

 

[lobo411]

Sounds like either the thermostat housing, which has no gasket but does use a bead of RTV, or the lower intake manifold gasket. A backyard mechanic can do the thermostat in about an hour, or the LIM in about 4 hours. Not hard at all.

 

[exporerfreak]

Sounds like either the thermostat housing, which has no gasket but does use a bead of RTV, or the lower intake manifold gasket. A backyard mechanic can do the thermostat in about an hour, or the LIM in about 4 hours. Not hard at all.

Thanks, we already started pulling the intake and almost have the manifold off and we are going to replace the gasket. hopefully that resolves both the front leak which can be seen and heard and there is another from the back side as well....which we can't see. :thumbdwn:

 

[702johnny94sport]

On the 1995 4.0 OHV motor, do you need to use the gasket maker on the thermostat housing? I remember having to do that on my 1994 sport with the older 4.0. I think on my 2000 4.0 sohc there was just a rubber gasket around the actual thermostat and the housing didn't need a gasket. Which way is it on the 95? anyone know?

 

[lobo411]

On the 96 OHV, you need to use RTV between the housing and the lower intake manifold.

 

[Lisa Dorsey]

Well, after replacing my thermostat I decided to do a write up on it. If you are needing to replace your thermostat, I highly recommend doing it yourself. It is easy to do, and very cheap.

Note: This is for the 4.0 OHV, not SOHC

First, a general disclaimer: I am not a Ford engineer, and do not work for Ford. Anything that you do, you do at your own risk.

Now to start. It should take about an hour to complete this, but giving yourself plenty of time is the first step. The tools I used are very common, and can be found just about anywhere.

Before you start, drain all of your coolant out of the car. This will make your life a lot easier down the road.

Tools used:
3/8" Drive ratchet
3/8" 2" drive extender
3/8" to 1/4" drive reducer
1/4" drive ratchet
10mm socket
8mm socket
Flathead screwdriver (not pictured)

Parts needed: Thermostat
New coolant

Now, where is the thermostat located?

It is on the end of the hose going to both the engine block and the radiator. It is where the hose bolts onto the block.

First off: The intake needs to go. Take off the latch for the filter, unplug the 2 plugs in the intake, and pull the vacuum line out. Now, unscrew the hose clamp with the flathead screwdriver, and remove intake.

Now there is that throttle cable cover there. That needs to be removed. Take you 8mm socket, and remove the 2 bolts holding that on.

After that is removed, remove the 3 bolts holding the hose on. These use the 10mm socket. It will take some experimentation with the different extenders/ratchets I have listed, but it can be done with just that. When you are loosening up the bolts and removing the hose, be prepared for coolant to leak from there. Have something underneath the front of the truck to catch it, Either an oil change pan or just some old towels.
Once removed, you will see this:

Please note that the thermostat shown in this picture is actually the new one, yours will not look that nice. It will also be wedged in there solid, and take some wiggling to remove.

When you place in the new one, be sure it is aligned the same way, and rotated the same way as the last one.

Now, put the hose back, and tighten in the 3 bolts. Then re-attach the throttle cable cover. Now put the intake back on. Be sure to re-attach both sensor plugs, and also the vacuum line.

Now, refill the coolant and burp the system.

You have now successfully changed your thermostat. Take it for a drive, then check for any leaks.

This is the old thermostat. Note how the gasket around it is worn and chipping.
Just remember, replacing your thermostat is easy to do yourself, and a lot cheaper too. Just take your time, and everything should go fine! If I have left anything out that you think should be added, be sure to add it or let me know!

Did all that now it wont start

 

[koda2000]

Tip: Check the wires going down to the crank position sensor. It's located on the lower left side of the crankshaft's harmonic balancer (behind the biggest pulley). If you disturbed/pinched the wires you may not be getting a signal for the PCM to fire the spark plugs. That's the most likely thing you may have done while changing the t-stat that would prevent the engine from starting.

Other than that, if you're getting spark and fuel the engine should start.