I've got a whole separate issue that a big group of Bullnose'rs are helping me with, so I figured I'd start a new thread looking for a bit of advice.

I put a new thermostat in my 85 i6 F150...put it all back together, filled it up, and it started leaking like a sieve in my driveway.

What did I do wrong?

I pulled everything off, cleaned off ALL the remnants of the old gasket on both the block and the housing...
I then used a new gasket with some gasket sealer. I put the sealer everywhere. On the housing, on the gasket housing side, on the block and on the topside of the gasket...then tightened it all down.

put some fluid in there...spilled out immediately in my driveway.

Did I miss a washer or a gasket or something?

Thanks y'all

JT

 

See where it's coming from. I never worked on a six, but I know the v8's are very difficult get back together without the thermostat slipping out of place and getting caught under the housing. Once this happens and you tighten it down, besides leaking it usually cracks the housing and ruins it.

 

Some gaskets have a peel & stick so no sealer would be needed.
When I was rebuilding the truck part of that was a new stat & gasket.
Well when looking the housing over I saw what looked like a dirt line and when I looked closer a ear broke off so I had to get a new one.
IIRC the stat fits into a lip in the housing are you sure the stat did not slip out? That is how I think the PO broke mine.
Again IIRC the stat fits in to the housing and then the gasket.
I would also check to make sure the housing is flat. Use fine sand paper placed on a flat surface and sand it a little bit.
Could it be a hose had crud between it and the housing and not sealing?
That is all I can think of ATM
Dave ----

edit; I also drill a 1/8" hole in the flat part of the stat to help bleed air and put the drill hole to the top.

 

thats 100% what happened to me...it was leaking out the bottom...I totally broke the housing trying to clamp it down...fml

 

All Felpro thermostat gaskets Ive got before had this double stick tape. What I do is place the thermostat in the housing and then use the gasket to stick it all together to hold it in place while installing it to prevent shifting.

I drill holes like you said on thermostats at work but on my personal vehicle I put the check valve at the top and never had to drill a hole to bleed the air.

 

Not related to the leak, but do yourself a YUGE favor and test the new thermostat before installation. Submerge the thermostat in an old pot of water on the stove. Heat the water and measure the temperature when the thermostat starts to open. Test the old one while you're at it, for confirmation it was bad.

I've had several thermostats bad from stock. OEM, name brand, discount store brand, it didn't matter. After learning the hard way, I always test now before installation.

 

Yep something I will be doing with my NOS Motorcraft 194*-196* thermostat. Not going to assemble the engine then get it all painted nicely then find out thermostat was junk.

 

I had the same prob on my I-6. I broke the housing over tightening it. I ended up using I think it was a gray permatex gasket product. If you look in the store it says on the label designed just for the thermostat housings. It worked great and hasn't leaked in a few years. Also might help to use vaseline to hold the thermostat in place while assembling. Torque wrench also helps but I didn't use one with the permatex and it came out fine

 

I just replaced my thermostat yesterday on my 1983 302 V8. I was stumped on how to keep that thermostat in proper vertical position when bolting the housing to the intake. There is a recessed area in the housing to accomodate the thermostat, but no real way to keep it there during the mounting process unless you slather everything with RTV.

My solution was to get a piece of thin wire (18g) and run it down the main throat of the housing (where the radiator hose connects) and place a small hook on the end to grab the thermostat. Once properly positioned, I bent the wire down at the throat to hold the thermostat in place. This held it in the correct spot while I bolted up the housing. Then I un-bent the wire, unhooked the thermostat, and removed the wire.

A little tricky, but it worked perfectly.

 

Another option is you can use some yellow weather striping adhesive, it also states it is a gasket adhesive as well. We've used that before to lock the thermostat in place to keep them from moving around if the gasket doesn't have a peal and stick adhesive in the first place.

 

Looks like you all were correct...again

I placed an order on Amazon, because my wife was freaking out about me shopping at Advance Auto during the Coronavirus era...
I got a thermostat housing a NEW new thermostat, new gasket and the elbow pipe that comes off of the housing (elbow pipe is still en route)

I pulled everything off, cleaned it all up, removed the old elbow pipe (blowtorch, WD40 and leverage) and started to put everything together.
The thermo housing was actually broken, not cracked. A big piece broke off when it was un-bolted.
So, I threw the housing back on with a new gasket and some sealer.
THEN I started to assemble everything else.

Funny thing...you cannot get the elbow pipe on with the housing attached to the block...at least I cannot because my smog pump is still attached and functioning. It does NOT swing far enough out of the way so you can twist the elbow pipe on.
So, I had to pull the mf'ing thermostat housing off again, and ruined the gasked in the process...spilling some antifreeze in the driveway, again...

I broke the house rules and went to Advance Auto and bought TWO new gaskets to finish the install, curbside delivery.

Got it all back together, started her up while I was burping the system and CLOSELY watched the temp gauge...the temp got up there steadily but then stayed on M (NORMAL) the whole time.
I then went for a nice drive and continued to watch, stayed on M the whole drive.

This was a long process but it seemed to have worked.
Thank you for all of the advice.
It really helped out a lot.