Pitted thermostat mounting surface...

Varilux · #1 08-20-2017, 05:05 PM

I'm replacing a cracked thermostat housing on my 2004 Ranger 4.0L (it cracked right at the seam behind the sensors).

I've gotten everything out, and I notice there is some pitting on the aluminum mounting surface for the housing- right where the rubber gasket makes contact. If I look at the bottom of the removed housing, sure enough I can see indications that coolant was starting to wear away the gasket at this point.

Since I don't want to do this job again anytime soon, I'm wondering what I can do to remedy the pitting. The options I'm considering are using just a tiny amount of JB weld to fill the pits (smoothing the surface flat with a razorblade), but I have a feeling the expansion of the aluminum and the JB Weld will differ, causing the JB to fail.

The other option I've been thinking of is using a small amount of black gasket sealer in that area (or all around the base of the housing).

Any suggestions would be greatly appreciated! There are two pits- the largest being maybe 1/8" across and 1/32" deep (can just feel it with a fingernail).

PS- Secondary question... When I ordered the parts (from Tasca Ford online), they listed a temp sender and a temp sensor (the parts arrive on Wednesday). However, looking at the removed parts (which I believe to be the originals) I actually have two sensors and no sender. I'm planning on using a new o-ring and resusing one of the sensors, but I'm wondering a.) why they would recommend the wrong part and b.) why Ford would have two identical sensors side by side!

Doctor Wily · #2 08-23-2017, 08:50 AM

Quote:

Originally Posted by Varilux

I'm replacing a cracked thermostat housing on my 2004 Ranger 4.0L (it cracked right at the seam behind the sensors).

I've gotten everything out, and I notice there is some pitting on the aluminum mounting surface for the housing- right where the rubber gasket makes contact. If I look at the bottom of the removed housing, sure enough I can see indications that coolant was starting to wear away the gasket at this point.

Since I don't want to do this job again anytime soon, I'm wondering what I can do to remedy the pitting. The options I'm considering are using just a tiny amount of JB weld to fill the pits (smoothing the surface flat with a razorblade), but I have a feeling the expansion of the aluminum and the JB Weld will differ, causing the JB to fail.

The other option I've been thinking of is using a small amount of black gasket sealer in that area (or all around the base of the housing).

Any suggestions would be greatly appreciated! There are two pits- the largest being maybe 1/8" across and 1/32" deep (can just feel it with a fingernail).

PS- Secondary question... When I ordered the parts (from Tasca Ford online), they listed a temp sender and a temp sensor (the parts arrive on Wednesday). However, looking at the removed parts (which I believe to be the originals) I actually have two sensors and no sender. I'm planning on using a new o-ring and resusing one of the sensors, but I'm wondering a.) why they would recommend the wrong part and b.) why Ford would have two identical sensors side by side!

RE Sensor/Sender:

The 2 parts may look nearly identical. They should be 2 different colors though. One is a SENSOR, for use by your computer, the other is the SENDER, used for your temp gauge in your cluster.

Can you post a picture of the pitting in the mounting surface for the housing? I personally would be hesitant to use RTV + the gasket, but I've always been told to not use RTV + gasket.

cowboybilly9mile · #3 08-23-2017, 09:10 AM

Quote:

Originally Posted by Varilux

I'm replacing a cracked thermostat housing on my 2004 Ranger 4.0L (it cracked right at the seam behind the sensors).

I've gotten everything out, and I notice there is some pitting on the aluminum mounting surface for the housing- right where the rubber gasket makes contact. If I look at the bottom of the removed housing, sure enough I can see indications that coolant was starting to wear away the gasket at this point.

Since I don't want to do this job again anytime soon, I'm wondering what I can do to remedy the pitting. The options I'm considering are using just a tiny amount of JB weld to fill the pits (smoothing the surface flat with a razorblade), but I have a feeling the expansion of the aluminum and the JB Weld will differ, causing the JB to fail.

The other option I've been thinking of is using a small amount of black gasket sealer in that area (or all around the base of the housing).

Any suggestions would be greatly appreciated! There are two pits- the largest being maybe 1/8" across and 1/32" deep (can just feel it with a fingernail).

PS- Secondary question... When I ordered the parts (from Tasca Ford online), they listed a temp sender and a temp sensor (the parts arrive on Wednesday). However, looking at the removed parts (which I believe to be the originals) I actually have two sensors and no sender. I'm planning on using a new o-ring and resusing one of the sensors, but I'm wondering a.) why they would recommend the wrong part and b.) why Ford would have two identical sensors side by side!

a) 1/32" = .031". If you can "just feel it with a fingernail", then realistically it's going to be under .010" and closer to the thickness of a sheet of typing paper. I'd bet you could zip it up and it wouldn't leak, but if you're concerned then IMO a thin layer of Permatex black isn't going to hurt, even though it's not normally used nor recommended.

b) Those are temp sensors or temp senders, whatever you prefer to call them.

c) They are the same part used twice.

d) One temp sender is for the PCM, the other is for the gauge on the dash.

e) I don't know where you're at in your project, but I posted some pics when I did some maintenance, including a t-stat housing last spring. You may find a reference to somehow be helpful. Linky: http://www.fordtruckfanatics.com/for...ad.php?t=40715

f) Contrary to popular belief and what the FSM says, both of these temp sending units can be removed without taking off the intake.

Edit: personal opinion, but given the history of the t-stat housing, I like using a torque wrench on the three hex screws that hold it to the head, and the three hex screw that pin the thermostat cover to the housing. IMO, to the greatest extent possible, on this one, equal is probably a very good thing.

Doctor Wily · #4 08-23-2017, 09:12 AM

Quote:

Originally Posted by cowboybilly9mile

a) 1/32" = .031". If you can "just feel it with a fingernail", then realistically it's going to be under .010" and closer to the thickness of a sheet of typing paper. I'd bet you could zip it up and it wouldn't leak, but if you're concerned then IMO a thin layer of Permatex black isn't going to hurt.

b) Those are temp sensors or temp senders, whatever you prefer to call them.

c) They are the same part used twice.

d) One temp sender is for the PCM, the other is for the gauge on the dash.

e) I don't know where you're at in your project, but I posted some pics when I did some maintenance, including a t-stat housing last spring. You may find a reference to somehow be helpful. Linky: http://www.fordtruckfanatics.com/for...ad.php?t=40715

f) Contrary to popular belief and what the FSM says, both of these temp sending units can be removed without taking off the intake.

^^ This guy is probably WAY smarter than I am.

Varilux · #5 08-23-2017, 11:25 AM

Here is an image of the pitting. I wouldn't be concerned if a.) it wasn't right where the rubber o-ring seals the surface and b.) I hadn't noticed the seepage on the original housing in the same spot.

Thanks for the info and advice! Regarding the identical senders, why couldn't Ford have used the same sender to send a signal to both the PCM and the dash (just curious if there is a reason- e.g., perhaps the signal cannot be "split").

cowboybilly9mile · #6 08-23-2017, 11:45 AM

Perhaps a better question would be, why couldn't Ford have used one sender, grabbed the temp data from the PCM via the vehicle network, and fed it into a digital engine temp gauge or display rather than an analog idiot gauge?

Varilux · #7 08-23-2017, 11:53 AM

So, based on the picture of the pits would you be inclined to just use the o-ring and call it a day (or would you use a thin layer of Permatex black)?

Doctor Wily · #8 08-23-2017, 11:53 AM

Quote:

Originally Posted by cowboybilly9mile

Perhaps a better question would be, why couldn't Ford have used one sender, grabbed the temp data from the PCM via the vehicle network, and fed it into a digital engine temp gauge or display rather than an analog idiot gauge?

I think they do that on some of the newer models. I've seen some housings with only 1 sensor opening. The other is blocked.

cowboybilly9mile · #9 08-23-2017, 12:05 PM

If it were me, I'd clean the mating surfaces, put down a thin layer of Permatex black, and install and torque the thermostat housing before the goop skins over. I would not use JB weld.

On the gauge, there came a point in time where Ford went entirely with the CANBUS network but they still used an idiot gauge. IMO, it wouldn't have been much $ at all to have a digital engine temp readout, and while they were at it, digital voltmeter and digital temp display for the 5R55E tranny (that data is on the network).

Varilux · #10 08-23-2017, 09:09 PM

VICTORY- at least for the moment!

I put a thin layer of the black Permatex on the mounting surface, but then got hung up arranging things and it started to stiffen. As I scraped it off with a razor, I noticed it left the little pits filled in perfectly so I cleaned everything else up and just used the rubber gasket.

I found the easiest way to get the housing back in was to install the senders first, get it close to in place, then attach the wiring to the senders. Based on advice here, I spent some time going around the three bolts easing them up to a little over 7.5 foot pounds (specs call for 89 inch pounds of torque). Tried to keep them really even.

I ran it for 30 minutes with no visible leaking. I topped it off cold and left the cap off waiting for the drop in coolant when the thermostat opened. However, the level never dropped (it just started seeping out the top). Finally I just reinstalled the cap and filled the overflow (I can see bubbles coming into it when we let off the throttle). Heater seemed to be blowing plenty hot, and the top radiator hose got hot but never got super firm.

Thanks for the tips- hoping this fix does the trick for a good long while!