'01 Ranger 4.0L Thermostat Housing Seal Leaking

[benjamming]

2001 Ford Ranger 4.0L SOHC with 150k miles
I replaced the thermostat & o-ring at 145k miles. It's been leaking since. Took it apart & saw that the upper thermostat housing was buggered up on the sealing surface. Installed a new Ford Motorcraft part (only $10 and made in Great Brittain!). Still leaks between the upper & lower thermostat housing. Took it back apart & the o-ring (Fel-Pro p/n 35617) doesn't fit tight around the thermostat, but I don't think it's supposed to as the housing does the sealing. Is that right? Also, o-ring looks a little flat but I torqued the 3 bolts to 89 in-lb per the factory service manual. Is there a trick that I'm missing? I've got another o-ring, but I wanted to check in to see if I'm not doing something correctly before installing & putting back together.

Thank you.

 

[Kira]

I've read about the housing.
The PO of my Ranger had it replaced at a local garage and I have no details. I've never given the thing a long, hard look.
I did read about a metal one which is supposed to be the cat's meow.
Go here: simmonsautosportz.com Look up the SA9. I think you can call 'em about it.

 

[Chris142]

Replace the bottom housing. That's what goes bad. Rarely does the top.

 

[Kruse]

The metal replacements SEEM to be a better replacement to the cheap plastic housings. They are available on ebay and RockAuto, at least, the last that I looked.
More expensive, but seem to be well worth it. If I ever have a thermostat leak, I'll use the metal replacement.

 

[benjamming]

Yeah the top was gouged along the sealing surface. Maybe it was fine, but I don't see how it would've sealed.

The bottom doesn't look bad. What should I be looking for as the failure? I would like to know for sure before removing the intake and all the other stuff. This should've been a simple thermostat replacement. Argh!

$135 for the Simmons metal one. Another Ford plastic one is $45 from online Ford parts department.

 

[Kruse]

Originally Posted by benjamming

$135 for the Simmons metal one. Another Ford plastic one is $45 from online Ford parts department.


There are cheaper alternatives to both the metal and the plastic replacements. The Ford plastic part will eventually leak just like the plastic aftermarket part will eventually leak.

 

[Chris142]

This is the sohc engine?

 

[benjamming]

Yes SOHC.

I just can't see how the lower is leaking as the sealing surface looks fine. Does it flex & cracks appear when under pressure that aren't visible when opened up?

 

[bdcardinal]

The whole thing leaks, you need to replace everything.

 

[benjamming]

So, is 150k miles about normal replacement interval?

 

[01rangerxl]

Yeah, I think whole housing replacement is the way to go. My friend recently tried replacing just the t-stat with the same result. Ended up buying a Gates complete housing replacement with a lifetime warranty.

When I worked in a shop that saw a lot of SOHC 4.0s, we only qouted the whole housing.

The better aftermarket metal ones like Simmons are one piece below the thermostat, eliminating a large potential leak point.

 

[GearJammer]

Do not get a Dorman lower housing whatever you do. Ask me how I know. This is one occasion where a genuine Ford part is worth every penny.

 

[benjamming]

So, are the 2 sensors typically replaced at the same time?

 

[bdcardinal]

Originally Posted by benjamming
So, are the 2 sensors typically replaced at the same time?


Ford does not sell the o-rings by themselves so we replace the sensors.

 

[nobb]

I'm not familiar with the 4.0, but on the 3.0 the housing is metal and there is no need to replace that. What I did notice is that the fiber gasket doesn't always seal perfectly even when you have everything cleaned up and torqued to spec. BUT over time (like a few months) the gasket expands and leak stops. Fel-Pro does make a top of the line gasket which has rubber ridges instead of the standard fiber gasket which should hold up much better. I think they should've designed the housing with more than the two bolts holding it which doesn't provide as strong/even of a clamping force.

 

[Falcon_LS]

Ford wanted crazy money when I was looking to replace the plastic housing on my Explorer, more as a precautionary measure. The thermostat was stuck open, so I figured this was the perfect time to replace it with an all-aluminum unit. I forget where I bought it from, I think it was Simmon's Autosports or something along those lines, but it was a fantastic two-piece replacement and cost half what Ford wanted for their plastic abomination.

 

[Kira]

To benjamming: You mentioned "2 sensors". FYI They are not!

We have one sensor (5v) and one sender (12v). Don't confuse them or interchange them.

 

[benjamming]

Should I be getting new bolts as well. Are there updated bolts for this mess or just the housing with the bottom seal? ?

 

[cb_13]

Replace the entire housing. Usually it is the lower portion that leaks. I was always able to replace the sensor o-rings out of a master o-ring kit we kept in the shop supplies section when I was a tech. But bdcardinal is spot on that Ford does not offer an exact replacement for the sensor o-ring.

 

[cb_13]

Originally Posted by benjamming
Should I be getting new bolts as well. Are there updated bolts for this mess or just the housing with the bottom seal? ?


No updated bolts that I'm aware of but if it has been leaking long enough they may break off and require being extracted with vise grips or drilled out.