HELP! Thermostat Gasket Question

I am in the process of changing out the water pump and thermostat on my 99 XJ. I finally got everything apart and started removing the thermostat gasket. I'm pretty sure it was the original because it was caked on there and extremely hard to get off. So I was using one of those throw-away snap blade knives (with the real thin blade that bends easily) along with a steel wire brush (pretty soft bristle that don't hurt your hand when rubbed against) as well as a nylon brush and some 1500 grit sandpaper. Somehow, there is some pitting under the gasket..... Will I have problems with this? Is there any way to fix it? Thank you for any replies.

no problem, if you have the sticky back type gasket put a thin layer of silicone on the other side, if not put a thin layer on both sides of the gasket and slap it back together.

make sure the thermostat is seated correctly before you tighten it down, if the thermostat slips out of place when you tighten down the housing it will crack.

I find that even with the sticky-tape-back-gasket-type I get leaks unless I put RTV on that side also. Basically, I always use RTV on both sides of the gasket.

Concur. Smear a little RTV on both sides of the gasket, bolt it in, call it done.

I like to smear RTV on the shanks & threads of the screws as well, if they're still okeh (if not, I'll replace them. Preference of material is bronze, brass, then CRES. If you're stuck using carbon steel, coat with RTV prior to installation. Threads are 5/16"-18

Alright thank you guys. Is it normal for there to be pitting in that area? I don't think it would have been possible for me to have done that using the tools I was....

it's probably just a flaw in the casting, I doubt you made those marks. it's not enough of a problem to effect the sealing surface though.

don't worry about it just put it back together :thumbup:

Just don't over tighten the bolts.

And make good and sure the thermostat doesn't slip out of place. I've had to do the job twice on two seperate occasions for that reason - I never cracked a housing, but it slips out of place & causes a leak.
+1 for a little RTF on both sides of the gasket & call it a day. You won't have any trouble.

Casting Areas that do not need to get machined rarely do and tend to appear pitted.

I have had poor results with RTV on thermostat housings, and no longer use it for that.

Take a flat file and true the (both) housing(s). Don't get fancy, make it flat (but don't take off too much). Iron housings don't tend to warp, but aluminum ones do.

Take the gasket. Put some Permatex #1 on both sides.
Look at where the housing bolts go. Do they enter water on the other side of the hole? If so, they need to be sealed also. Apply some PT #1 to threads.

Install the T-Stat and assemble. Go ahead and torque to needed spec, and fill up with water. No need to let it dry.

Nobody likes my method?

First, I use Permatex number 2--non-hardening.

I put a little around the flange of the thermostat to hold it in place, and then I only put the Permatex on the side of the gasket facing the thermostat housing--the part I can walk over to the wire wheel with and clean it up quickly the next time it needs changing.

Always works for me.

I avoid rtv like the plague, It damn near always leaks for me, "great stuff gasket maker" has never let me down, and you don't have to wait for it to cure... It's a little bit more expensive, but I hate doing repairs more than once....

Joe: That'd work well too.The reason I true the housings instead of just cleaning them is probably a left over from my V8 318/360 days with aluminum intakes and aluminum T-Stat housings. If they were not true, they would leak - like a sieve.
Pernatex both sides? Same reason. I did it once and it worked. When it worked, I stopped looking for other ways of wasting my time with a $5 part

XCM: I agree, I just hate doing a job 2X, especially one that is as seemingly simple as changing a T-Stat!

I've never had good luck with a paper gasket on the cherokee thermostat housing. With only two bolts, I don't think it gets a very even clamping force on the gasket, and I always see leaks on the bottom right of the housing. Even with pristine surfaces.

I know RTV is often time overused, but it seems to be the only way I've been able to get a leak free housing.

Awesome. Thank you for all of your replies. I ended up buying Fel-Pro gaskets (which already come with a bead of silicone on one side) and then I used my finger to smear an extremely thin layer of water pump specific permatex on the other side. Then I torqued to spec. One issue I was slightly concerned with was the amount of rust/corrosion inside the block where the water pump and thermostat sit. I opted out of using a chemical flush. Instead, I used a Prestone flush and fill kit as well as performed separate back flushes of the heater core, block and radiator with the hose. I plan on filling it completely with distilled water tonight, running it for 10 minutes with the heat on and then draining it and refilling with 50/50. As I have seen with many threads, I'm sure I will have to flush it multiple times for it to remain clear. The overflow bottle was pretty badly caked with mud. So my question is, will the rust inside the block ultimately go away or is it something I should be concerned with? If I have to, I will flush it with a chemical, but I would prefer to just keep flushing with distilled until clean and rust free. Any thoughts?

YES, go with distilled water.
If you go chemical flush you run the risk of dislodging too much crap at once & it can jam up in the radiator / heater core tubes. You'll get a lot of it out at once, sure, but I'd worry about collateral damage.
Another technique is to disconnect both hoses at the radiator & garden hose both the block & the radiator. note the if you block flow out of the radiator, you run the risk of popping the darn thing - garden hose = much more pressure than it's designed to hold.
Anyhow, cleaning it all up until the water looks clean is a good idea.

I don't flush systems, it's a waste of good water.

I also don't use distilled water, though I can see where that is an issue in some parts of the country where the water is barely potable as it is, let alone putting all those minerals in the cooling system.