I'm stupid & I need help with a Ford thermostat problem

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wavinwayne

wavinwayne

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DISCLAIMER: I FULLY ADMIT THAT I AM A BIG MORON

This morning, I noticed anti-freeze leaking from around the thermostat housing on my '97 Expedition 4.6L. I think I put the thermostat o-ring in wrong when I replaced the thermostat a couple months ago.

Simple question; On the '97-02 Expedition/Navigator/F-150, can someone tell me EXACTLY where & how to install the thermostat o-ring? I need advice from someone who is familiar with the '97-'02 Ford 4.6/5.4L engines.

My Haynes Expedition/F-150 repair manual is very un-clear on the o-ring placement, since it covers the V6 & V8 models of the F-150.

Thanks in advance for helping me to correct my stupid mistakes.
 
Unfamiliar with thermostat installation procedures, but I think there might be another problem. I know the 4.6 in the Crown Vic from 96-2000 (IIRC) had problems with the nylon composite intake manifolds cracking and losing coolant. I don't know if the same applies to Ford SUV's and truck with the 4.6, but it might be worth looking in to.
 
55,

Thanks for your reply. FWIW, Ford Expedition 4.6L engines do not have the plastic intake manifold. They are all aluminum.

Still looking for an answer on my original thermostat o-ring question.
 
wavinwayne,

You could very well be the smartest guy on this board. You think you can fool everyone, but you can't fool me.
nono.gif
 
My local Ford parts guy will sometimes print out digrams, which helps a lot. For the older car I purchased an Alldata account, which has a very useful online handbook. I purchased the account as even though I have the Ford factory servcie manual, you need another much more expensive factory manual for a lot of emissions related work.

In general make sure that mating surfaces are clean, and then make sure that they are flat. I'll often touch up surfaces with a flat sharpening stone, and if they're out a lot I'll 'mill file' or use some wet/dry paper on the stone. Consider yourself warned though, as if you aren't familiar with how to flatten surfaces you'll often make them worse. Once the surfaces are clean and flat, make sure that the gasket stays in place during assembly, use a sealer if required, and torque to spec in stages.
 
quote:
Originally posted by got boost?:
I can't answer your original question, but if it is that tough, just use rtv instead of an o-ring. it's possible the sealing surface is damaged, in which case you'll have to use rtv anyway.
Click to expand...
I think you realize leaving out the o-ring is bad advice. However, all o-rings need some lube on them (compatible with the type of rubber) during installation. In case of poor mating surfaces, you might find it necessary to also use some type of sealant. But you knew this already, right?
 
Well,

Right or wrong, I just replaced the o-ring with a new FelPro o-ring, that appears to be made of silicone; It's some type of orange rubber.

To make a long story short, I'm pretty sure (now) that the o-ring was supposed to go on top of the thermostat, & I had originally put it on the bottom, a couple months back.

Today, I put the new one in on top of the thermostat, drove it around for a while, got home, checked for leaks & all seems to be ok now.
 
quote:
Originally posted by got boost?:
why is it bad advice?
Click to expand...
Sealant alone can't substitute for the correct o-ring on a properly designed seal. There are well-proven engineering guidelines for designing with o-rings. Usually the fluid pressure helps make a seal by compressing the o-ring inside its groove.
 
quote:
Originally posted by got boost?:
rtv would be fine. the o-ring was used for cost only.
Click to expand...
You obviously are not familiar with the Ford 4.6L V-8. The only thing RTV would do in this application is make one huge mess, & possibly clog up the thermostat.
 
I finally found some decent pictures that show how this thermostat assembly fits together.

This is how it looks with the thermostat housing still attached to the intake manifold, with the upper radiator hose removed:

-


Here are a couple of pictures that show the thermostat housing, o-ring, & thermostat, in order of assembly.

-


-


Regardless, I've got it fixed now.
smile.gif
 
FWIW, the new (silicone?) gasket that I installed was a FelPro #35489. I picked it up at Advance Auto Parts for around $5.
 
I can't answer your original question, but if it is that tough, just use rtv instead of an o-ring. it's possible the sealing surface is damaged, in which case you'll have to use rtv anyway.
 
o-ring = less labor to install, silicone rtv = works just as good. o-rings require a good surface finish to work. I have seen many o-ring sealing surfaces that were corroded (happens if coolant is not changed) and wouldn't seal with an o-ring, in that case either use rtv or replace parts. in those pictures the parts look just fine.
 
quote:
Originally posted by got boost?:
o-ring = less labor to install, silicone rtv = works just as good. o-rings require a good surface finish to work. I have seen many o-ring sealing surfaces that were corroded (happens if coolant is not changed) and wouldn't seal with an o-ring, in that case either use rtv or replace parts. in those pictures the parts look just fine.
Click to expand...
No, just no to your whole reply.

The o-ring is there for a reason. If put in the right place (over the T-stat) it forms a compression seal (notice the beveled surface at the bottom of the t-stat housing)?

There is no machined surface that can use RTV on that housing. 10 years in a Ford shop and never saw one leak. Ford engineering must have done something right on that one.
 
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