Thermostat backwards?

Buggyman · Nov 28, 2015

Hey guys,

My brother just gave me his 1998 Ranger back, I gave it to him about 5 years ago after I did a lot of work to it. He replaced the water pump and thermostat and then the truck started to overheat badly. We trailered it to my house after it sat for a year and I have it running again. I checked the thermostat and it looks like he might have installed it backwards. I flipped it around and let the engine warm up and the top radiator house stays cold until the engine is hot then the hose gets firm from the pressure and warms up to very hot. What is the proper orientation for the thremostat? I have it installed backwards to how the shop manual suggested, (i.e spring toward engine). I used my finger and pushed the thermostat open and it opens in the direction of the spring, (i.e springs holds thermostat shut) and put it so that the spring side is positioned toward the upper radiator hose.

I know this is such a simple question but I want to make sure its facing the right way. Its a 2000 3.0 Flex fuel motor in a 1998 body.

Thanks guys,

Philip

RonD · Nov 28, 2015

Spring on thermostat goes on engine side, there is a type of wax in the center cylinder that melts and expands when heated, it pushes against the spring to open valve.

It can be installed backwards and still work because metal of thermostat transfers heat fairly well, but it would open at a higher temp than spec, probably 10-20deg higher.

There is no "pressure" in the cooling system to push open the valve, the water pump just circulates fluid, via the by-pass when t-stat is closed, and then via the radiator when it is open.
Bypass is a smaller opening, heater hose, so when t-stat opens it is the path of least resistance, but heater hose still gets enough circulation to heat up cab, if needed.

Buggyman · Nov 28, 2015

Thanks Ron, that was a great explanation and makes sense. Could it have just been a bad thermostat that he bought? He said the water pump fins were nearly nonexistent but its overheating very quickly since he replaced the T-stat and water pump.

shane96ranger · Nov 28, 2015

Has the system been properly burped? It sounds like you might have air in the system. Did the thermostat get installed with the pellet clocked at 12 o'clock? It's a PITA to burp them if that pellet is clocked wrong, or backwards.

RonD · Nov 28, 2015

The poor circulation from the old water pump could have caused other issues if engine was overheated for any length of time.

Metal expands when heated.
Hottest part of an engine is the top of each cylinder and head, thats where the fuel is burned and it gets HOT, cooling system surrounds this area to transfer that heat away.

A head gasket has a metal ring for each cylinder to seal the block to head fitment.
These metal rings are compressed by tightening down the head bolts to specified torque.
When engine heats up block and head metal expands, and since the head bolts are in place the head gaskets rings get slightly more pressure because of this metal expansion.
This is engineered for in the design of the block, heads and gasket.

When you overheat an engine the metal expands more, this can cause one or more of the metal gasket rings to be crushed because of the "over expansion" of the block and head metal.
The metal ring can no longer seal cylinder's 1,000+psi of pressure when firing so some of that pressure escapes past the ring.
Since each cylinder is surrounded by cooling passages this pressure usually finds its way into cooling system.
The pressure is "air"(burned air/fuel, exhaust) from inside the cylinder, so being "air" it goes up to top of head, and since air doesn't conduct heat as well and displaces coolant cylinder gets even hotter.

So basic rule of thumb is DO NOT overheat engine

DO NOT try to make it home, at first sign of overheating pull over, let engine cool off.
After cooling see if you can see the problem, you can drive it short distances, allowing it to cool off in between.
Low coolant from a leak, $10 broken hose, or $40 water pump could end up costing you hundreds of dollars in replacing head gaskets because "you tried to make it home", heck, even a $300 towing bill is cheaper than head gasket replacement.

If you think the engine may have been overheated, then I would do The Glove Test, just to take head gasket issue off the table as being the cause of current overheating, it is a free and easy test.

Test is posted here in #7: http://www.therangerstation.com/forums/showthread.php?t=164473

Buggyman · Nov 28, 2015

Thanks, I will try the glove test. I suspect a blown head gasket, my brother does not think he overheated it too much but it did overheat on him while driving and I know he let it cool down some then kept driving it home. If I have to end up replacing the head gaskets, what else would you suggest replacing while its torn down? I like to avoid an entire overhaul right now but I also want to make sure the problem is fixed while its broken down.

Thanks again,

Philip

RonD · Nov 28, 2015

Just the head gasket kit, and with that kit you will get new valve guide seals.
I would have a machine shop clean, surface and pressure test heads, they will often install the new valve guide seals for "free" or only small charge.

1999 and up 3.0l used different length head bolts.
Good read here on 3.0l changes over the years: http://www.therangerstation.com/tech_library/3_0-build.shtml

You already have new water pump and t-stat, if rad cap wasn't replaced then I would do that, if there is a bad head gasket then spring in cap will probably be bad.

back flush heater core.
inspect core plugs(freeze plugs) on side and front of block for rusty spots, replace if in doubt, rubber expansion plugs are fine to use, just more expensive.

Buggyman · Nov 30, 2015

I did the glove test and at first the glove did have some bounce to it, not much but it did slightly inflate and deflate as the engine turned over. It does not do it consistently though. Could the water pump cause the glove to inflate slightly? I will probably get the the tools to compression test each cylinder to find out for sure.

RonD · Nov 30, 2015

Remove/loosen fan belt and take water pump movement out of the test.

But no, water pump just circulates coolant it shouldn't cause any pressure differences.

Glove moves because some of a cylinder's 160+psi pressure is finding it's way into cooling system, which of course shouldn't happen.
It should continue to bounce however each time that cylinder is on compression stroke, and then deflate on that cylinders down stroke, so bounce up and down.

Buggyman · Nov 30, 2015

I compression tested the drivers side of the motor tonight (ran out of time to do the other side but not sure what difference it would make) and first cylinder read around 150-160 psi, second cylinder struggled to produce 60 psi and the third had around 120 psi. I am assuming blown head gaskets and perhaps even cracked heads, I feel like I can smell fuel in the radiator as well. Not sure at this point if I will attempt to pull the heads off or not. The power steering is having issues, the rack needs to be replaced and the pump makes a lot of noise. Rest of the truck is in rough shape and not sure if I will have the time to put into rebuilding the engine.

Thermostat backwards?

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