having a PITA time changing the thermostat, please help

[atfrith]

I want to change out the thermostat on my 90 XJ cuz its been a couple years and i've gotten the top bolt off of the thermostat housing, easy enough, but the bottom bolt is hidden behind the serpentine belt. I cant get a socket in there for the life of me without taking off the belt or at least loosening it. But i can't seem to loosen the belt. I loosened the two bolts on the tensioner pully (the pully on the far right) and the powersteering pump still isnt moving anywhere to loosen up the pump. Any ideas?
heres a pic from under the jeep looking up at the two bolts i loosed on the tensioner pully/powersteering pump thing.

 

[xjmatt]

There are 2 more bolts on the back of the power steering pump. Those need to be loose as well for the pump to slide so you can take tension off the belt. So 4 bolts total.

 

[atfrith]

sweet thanks, i'll go try and find those now

 

[atfrith]

ya, i could only find one more bolt on the back of the steering pump

 

[5-90]

The other one is toward the bottom of the bracket. It's easier if you have a 13m/m wrench with a long handle, but it can be done with a standard. I can't, for the life of me, get a socket wrench down there tho...

I'd suggest replacing the thermostat bolts while you've got them out - they're threaded 5/16-18, but two different lengths (I think they're 1" and 2" long, or thereabouts.) Brass is best, stainless is good, but don't bother with plain steel. Rust sucks, and having to drill those bolts out is a HUGE pain!

If all you can get locally is plain steel, I'd suggest you coat the bolts with RTV before you put them in, and buy several (so you can replace them each time you have them out. Cheap insurance - paying to have a bolt drilled out hurts a lot more than just replacing the damn things...)

5-90

 

[atfrith]

Alright well i finally got the belt off, replaced the thermostat. filled it up with coolant through one of the hoses, i think the upper radiator hose, the one where i have the do it urself flush t-fitting. I filled it through there until coolant started coming out of the other larger hose that connects to the thermostat housing. connected up the hose, and put a little more coolant in. I drove the jeep around for like 20 min, temp didnt get high at ALL, stayed under 210, i was all excited that i fixed it. I pull up at my house and get out, the i turn around and see coolant pouring outta the overflow tank again. What the FU*K!!! but i turned the key on and the heat was still just barely above 210, so its still not overheated at all. Could it be that i just filled it up with too much coolant?? I dont know what else could be wrong, new waterpump, new thermostat, new cap and bottle....
and now that i think about it...after i filled up the radiator through the hoses, i topped off the overflow tank to the full line...probably souldnt have done that...

 

[5-90]

Looking down through the fill hole, you'll see a "post" in the tank that has a half-cut on the top part. The coolant level is supposed to be over the "full" part of the post, but not over the "half" part. If you fill it too far, the coolant WILL expand as it gets hot, and it WILL overflow at first. Don't refill just yet, unless it's actually low.

5-90

 

[atfrith]

AHHH, i always thought the full line was that big line that goes around the entire tank, about half way up. Well anyway, i parked it and took the cap off while it overflowed a little bit of the coolant (not a LOT, but not a little either), and i just left the cap off and came inside to ask you guys whats up. So what should i do now, the overflow tank is empty, cap is off, engine is cooling down and off..

 

[5-90]

No, that's the parting line for the moulds.

If you're going to top off coolant, you'll want to have your engine idling, and add SLOWLY (or just let the thing sit for 4-6 hours.) Cracked blocks suck.

Dumb question, but did you put in your thermostat "as was?" I've posted quite a few times on drilling the thermostat for the RENIX system (it's the only mod the system REALLY needs!) to make the system purge itself of air. If you haven't done that, you'll want to jack up the rear of your rig until the rear of the cylinder head is higher than the front, and then loosen the temperature sensor at the driver's side rear of the head. It's safe to assume you have an air pocket behind the thermostat, and that will cause you headaches. Loosening the temperature sensor (when it's elevated,) and topping off coolant until it starts to come out past the sensor should purge the air bubble.

If you have an air bubble behind the thermostat, the thermostat WILL NOT OPEN and you'll end up with an overheat!

If you're going to purge the system by pulling the sensor, I'd advise letting the system sit and cool off for a minimum of two full hours - go have lunch or something...

5-90

 

[atfrith]

Ya thats what some other guys on jeepforum are recommending me do as well. No i diddnt drill the hole, i should have, but there is no way im goin back in there to do it now, haha. One question though, you said to slowly fill it with coolant till it starts coming outta the temp sensor hole, but where exactly shoudl i fill it? Through the overflow tank? or through one of the hoses?

 

[5-90]

Through the fill cap is fine.

Just FYI - if it's part of the pressure system (like ours is,) then it's not an "overflow" tank. It's properly referred to as a "volume" tank, because it provides space for the coolant to expand. If it was an "overflow" tank, it would just have a dust cap, rather than a pressure cap. Just so you know...

Typically, in the closed cooling system, those tanks are referred to either as "volume tanks" or "surge tanks." Either is correct.

5-90

 

[atfrith]

Sweet thanks for lettin me know, i didnt know that. Well anyway, i just pulled the temp sensor, nothin, i didnt hear any escaping air at all. And i JUST replaced the cap and bottle before doing all this, and now that it spewed again, the fu*kin cap wont stay tight again...

 

[5-90]

If there's no pressure in the system, you won't hear any air rushing out. If you're doing it right (I don't recall as I'd mentioned,) you've pulled the pressure cap first, so there WON'T be any pressure in the system.

The critical thing is that you get to SEE coolant coming out past the sensor, that's what you're looking for. If you don't see anything, you've got an air pocket to get rid of. Pull the sensor (keep it handy!) and slowly add coolant until you see it come out that hole. When you do, put the sensor back in and tighten it down. Top off the last little bit, then replace the pressure cap and start the engine. You MIGHT see the coolant level drop in the volume tank a bit more - that's fine, because the thermostat opened and is allowing flow. Remove the pressure cap, top off (SLOWLY!) and reseal. Drive around for a half-hour or so, and pull in and check the coolant level again - it should be just fine now.

5-90

 

[atfrith]

hey thanks a lot man. Only thing im worried about now is that cap not holding pressure, i can get it snug but if i try to tighten it down all the way, it re-loosens itself, so i have to stop tightening towards teh bottom. Anyway, i pulled the ssensor, added coolant until it came out of the sensor hole, put the sensor back in, now im gonna go do what you said, thanks again and i'll let ya know what happens

 

[atfrith]

ya, just got back from driving it around. Let the temp get up to like 210, stayed put. I saw the thermostat open as the coolant dropped below 210, kinda hovered around there. I park it, get out, coolant is boiling outta the tank again. WHAT THE FUC*!!! Please tell me i just have to replace this damn cap again

 

[5-90]

How old is the cap, and how old is the tank? I typically change both every four years - and I get them from Morris 4x4 Center (www.morris4x4center.com) cheap enough. Considering the dealer wants something like $50 for the tank and $10 for the cap - and Morris wants something like $25 for the tank AND cap, you tell me what I should do? They're cheap enough there that I can afford to keep a spare on the shelf for emergencies, and a couple loose caps for "just in case" in the glove boxes of both DD's...

5-90

 

[atfrith]

I just bought the tank and the cap new off ebay like 3 weeks ago, it held nice and tight up until today when it spewed again. But now when i go to tighten the cap, it'll get semi-tight and then re-loosen again. So i have to start to tighten it and stop before it loosens itself again.

 

[atfrith]

Alright, well i think ive narrowed my problem down to the dang bottle/cap. I've had them crap out on me like a total of 3 times already, the cap not tightening that is. But which part exactly is crapping out? Is it the bottle or the cap that is making it so it wont tighten? I'm guessing its the heat that deforms them or something. But i dont want to keep buying new bottles along with the cap if its only the cap that needs replaced, and vice versa....