Let me tell you a story...

about an obnoxious leak my Jeep has.

89 Limited auto. 145k on the clock.

The temp needle has never really gone to 210, it always stays at like 180ish and the aux fan turns on for no apparent reason when it doesn't need to.

So the other day I go to warm up the Jeep in the morning, go out 7mins later to find a puddle of coolant on the ground and more dripping out. Took the Tacoma instead.

So my wife and I start checking out the cooling system, the lower rad hose had about 5 pinhole leaks. So we think it's that, I have my wife drive to the store to get a new one, and an upper rad hose as well since it was showing signs of wear, and also got some tubing for the other cooling lines since we were already doing it.

In the process of taking off the upper rad hose, the neck that goes into the radiator and to the upper rad hose, was busted, it was just shoved into the radiator.

So...4 days later, our CSF 2row radiator gets here from Radiatorbarn. Nice and shiny black. Get it installed along with a new lower/upper rad hose and other coolant hoses. Also installed a new 190 t-stat and gasket, sealed that sucker up nice.

So today we finally get it all in and start putting coolant in. About a bottle of coolant and a half later, it seems about full, then we start seeing a leak. Sonofa***** ...

So I get down there and check things out. The lower rad hose hadn't been tightened enough. Fixed that leak, however...there was a lot of other areas with coolant.

Now is time for the picture story:

Just below where the lower rad goes into the block


Nice little pool of coolant...It appears that it's coming from this next picture...


Down in there you can see it's wet, thinking the above pic is the runoff of the leak from this area since the block is angled back a little bit. What would this leak be from? It had a slight leak there before when we bought it. The t-stat housing got rtv'd pretty good and a new gasket...


Also right below the pulley system...could be from the leak by the t-stat housing


Dripping by the alt as well


Drip going back down the belly and quite a good drip there going



Soo.. where do I start with this?

Clean all the drips off. Rig a pressure tester up, that part may be fun due to the Renix coolant bottle- unless you went with the newer style that uses a conventional radiator cap? Pressurize the system and see where it's leaking. That's really all there is to it.

Your problem happens a lot- fix one thing and something else starts leaking. A leak keeps the system from developing rated pressure, then when the leak is fixed the newly restored pressure blows out elsewhere.

How does one do a pressure test on the cooling system?

JJacob's is giving some good advise there. Also, on my 93' there is a weep-hole check for the water-pump. if you are getting leakage there (if that is even applicable to your Renix model), that COULD mean a bad water-pump. That's just one of the things i recall from my FSM.

Good luck!

You can get a pressure gauge from the parts store to connect to your radiator (where the cap would go) to test for pressure. not sure if you can rent it or if you have to buy it.

Purely a guess based on pics, but is your thermostadt housing leaking?

Based on location it looks like thermostat housing gasket, but it could be the water pump gasket too. It's possible that coolant is riding the belt and getting thrown into that gap but very unlikely.

Easiest thing is go get a Felpro dry gasket for the thermostat housing from autozone ($0.99) and replace the one that's been coated in RTV. The housing only has a couple of bolts and it will leak pretty easily.

There is a dry gasket between that RTV. It's not just straight up RTV. Thought for sure I did a good job on sealing the t-stat housing. I guess I can try it again though. Just seems odd there's so much coolant in different places. Even let that sob sit overnight so the RTV could dry properly.

How would the coolant get down towards the alt though? Should I check the belt to see if it's wet I take it?

If it is the water pump, how hard is it to replace a gasket or the pump itself? Never done the water pump before, just t-stat.

Well some of your pictures look just like my 94 did 2 days ago. Get a flashlight and look up behind the water pump pulley from underneath the Jeep. You should see the weep hole. If there is coolant visible that is probably your main suspect. I just did mine (as well as a couple other things). Not really a write-up but it's here:

http://naxja.org/forum/showthread.php?p=244851236&posted=1#post244851236

Another good place for info:

http://www.cardomain.com/ride/325707/17

Good luck with it and let us know what you find.

Bdiddy11 said:

There is a dry gasket between that RTV. It's not just straight up RTV. Thought for sure I did a good job on sealing the t-stat housing. I guess I can try it again though. Just seems odd there's so much coolant in different places. Even let that sob sit overnight so the RTV could dry properly.

How would the coolant get down towards the alt though? Should I check the belt to see if it's wet I take it?

If it is the water pump, how hard is it to replace a gasket or the pump itself? Never done the water pump before, just t-stat.

Click to expand...

If you can do the t-stat you can do the pump. Just make sure you loosen the pump pulley bolts BEFORE you take the belt off

You will have to take the power steering pump bracket off, but you can just set it aside, and you don't have to disconnect the lines.

Anyway, I just did this, it's an afternoons worth of work.

Also, I've found that RTV on top of the gasket doesn't tend to work well. Either RTV it, or use the gasket dry, those are the two methods that seem to work for me, and I've done a crap ton of t-stat gaskets, because I can never seem to get a stat from the parts store that works properly. T-stats are a dealer only item for me anymore.

I purchased a felpro. Used rtv. It leaked like a sieve.

I purchased another felpro. Installed it dry, no issues what-so-ever.

So a dry gasket on both sides then? No RTV whatsoever...

That's the only way it worked for me!

That's right, use the Felpro and leave it dry.

Aight, i'll give that a try tomorrow. If that is the only issue i'll be happy! I wanna get this thing back on the road.

Kinda sucks going through the work of all new cooling hoses and shiny new radiator only to have leakage.

hightime81 said:

JJacob's is giving some good advise there... Also, on my 93' there is a weep-hole...

Click to expand...

That'd be my first guess. If the waterpump hasn't been changed out recently I'd suspect the weep hole as it's at the bottom most point of the engine and under the influence of the fan. The coolant get blown all over the botttom of the engine, belly, sway bars etc.

96XJ_4.0 said:

Purely a guess based on pics, but is your thermostadt housing leaking?

Click to expand...

...and that would be #2

Bdiddy11 said:

So a dry gasket on both sides then? No RTV whatsoever...

Click to expand...

IMHO I think it's easy to install the thermostat without a good seal. Since you have to "stick" it to the block and then put the gasket on...it's easy to slightly misalign that connection.

Personally I always put a couple of tiny dabs of RTV on the t-stat, to keep it in place. Then I smear a thin coat of RTV on both sides of the gasket, then put the whole thing together. So I vote RTV AND the gasket.

...and finally, I had a true pin-hole leak in my pressure bottle. It would only leak when the truck was running at temp. It shot a tiny stream of coolant that hit the back of the A/C compressor and presented itself as a leak from the front of the engine.

So, like JJacobs sez, clean it up, watch it run.

Tip: Use a flashlight with a LED bulb, tends to make coolant "glow" bettter.

It amazes me that cars had gaskets that sealed for about 80 years before RTV. How did they retain their liquids without gobs of RTV smeared all over the gaskets?

honestly, I don't bother with paper gaskets anymore. My block is so badly pitted from being 23 years old and abused that they just don't seal anymore.
So it's straight RTV for me, no gaskets, and applied correctly RTV isn't messy, it looks just like a paper gasket on my motors, a thin red band with no squeezed out globs, but it does conform better to my badly pitted block.
The trick is to let it dry for an hour or two before you torque down the component.

Thermostat housing:

Clean both surfaces completely--the smallest piece of old gasket will result in a leak--scrape, wipe clean, inspect with a bright light, scrape again.

Now, use Permatex non-hardening and apply a thin layer to the thermostat housing surface, with a little bit into the housing recess for the thermostat's flange--that will help hold the the thermostat in place during installation. Do not put anything on the head mounting surface, that way there will be a minimal amount to clean off next time. Put the gasket in place on the housing. The Permatex will hold the gasket and thermostat in place while you position the housing and start the bolts. Tighten both bolts making sure you cinch them down equally, alternating bolts.

So... still leaking with a dry gasket. Seemed to be leaking from the t-stat housing again, so I tightened it down even more...I thought I had it down pretty good the first time, but after I turned it on for a second it started leaking again.

So i've got the t-stat screwed in even tighter now.

In the process, I realized a couple things...

This appears to be broken... or is it supposed to be like that?


Still had some leaking following the line back between the pan and the upper part


Still had some leaking right behind the pulley, tightened up those bottom bolts in yellow, and all the similar bolts along the side where picture 2 was leaking. Some didn't need it, some did, dunno if that will help or if there's a gasket there that can go bad?


Last thing I realized, this gasket here, appears to have some issues... that's where a lot of the drippage was coming from, when it put my finger up there, more came out. I'm wondering if that gasket went bad and could be contributing to the leakage? There was a lip there that was rather moveable and had quite a bit of coolant


So i'm not sure where to go next. Gotta wait to find out if the part between the bottom pan and upper block has a gasket that goes bad or bolts just needed tightening, if the gasket in front behind the pulley has gone bad and that part behind the pulley that appears broken...


Thanks!