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Changing lower radiator hose on '90 Closed System.

BIGSLVRXJ

BIGSLVRXJ

NAXJA Forum User
Location
Des Moines, Iowa
I will be doing this little project this upcoming weekend. The hose doesn't look like any trouble to get off and yes I know I have to get one with a spring in it, but I guess I have several questions.
1. My cooling system has never been "flushed" that I know of. The radiator was replaced two years ago, but I did not have it flushed. Should I go ahead and drain all the coolant out and spray a garden hose around in everywhere when I do this? I guess the other option would be trying to save some of the coolant in there, but I'm probably better off just draining it at that point huh? There is some brown sediment in the bottom of my coolant bottle also(hoping it's not oil).
2. If I drain it all out am I going to have to screw with purging the friggin' system? If so can someone post the procedure here so I can find it again quickly/easily? I know its something to do with the CTS.
I really appreciate the help everyone.
Collin
 
You'd do well to flush the system - even if the radiator's been changed, when's the last time the block was cleaned? Do the flush, then change the hoses afterwards.

If you're going to change one hose, do the smart thing and change both. It saves you some worry.

If you want to make things very simple for yourself later, get in the habit of taking your thermostat and drilling two 1/16" holes in it. Install it such that there is one hole at 1200, and the other at 0600. This will make the system "self-bleeding," since the upper hole will pass air out of the system to the surge tank, and the lower hole will pass water in to displace the air from the system. I've been doing this for years, and it works well. This solves the entire problem of bleeding the air from the RENIX system, and has no ill effects. I'd go so far as to say that you might want to go ahead and "field modify" a thermostat and see to that now so you don't have to worry about it later.

5-90
 
To purge the system, pull off the upper hose at the thermostat.

Pull the temperature sensor out at the back of the head.

Then hold the upper radiator hose up above the valve cover.

Then pour water/coolant into the hose until it comes out of that sensor hole. What you are in a sense doing is making sure liquid is at the thermostat so that it will heat up and open to start the flow.

Put the hose and sensor back on and start the engine with the "turtle" cap off.

watch the temperature just in case something didn't come out right. Water should start flowing back into your turtle, add more water/coolant to keep the level up until it stays at a good level.

tada!

I'll let someone else give you a good run down of a flush.
 
While I understand the "why" of it all, I've never quite understood the whole "how to" and "what's happening" of burping the cooling system. Does putting holes in the thermostat negate the need to burp the system? TIA

I agree about the hoses however,... in fact when my upper hose burst a few years ago I had a mechanic, yes I used a shop, replace all of the coolant carrying rubber hoses since they were all the same vintage.
 
Yeah I changed the upper radiator hose out about 4 months ago without burping the system and it still ran fine. That being said I guess I probably don't need to replace that again but doing the lower one I figured I would lose a lot more coolant, which is why I thought I might as well do a flush which would mean burping it as well.

Oh and 5-90 could you elaborate on this method for me a little bit. I've changed the thermostat out several times but I'm not really picking up on what you're saying. I remember when I did it the first time I crushed the little gold pin that goes in and out so I had to replace it about a half day later (2 thermostats in one day). So because of that gold pin I thought there was already a certain way it had to be installed. Anyway if you have time or if someone else can shoot a little info down this way thatd be great.
Thanks everyone.
 
Last edited:
he's just saying to drill a hole at the top and bottom of the thermostat so that water (small amount) can pass without it being open, this removes the need to "burp" the system.
 
WobblesXJ said:
he's just saying to drill a hole at the top and bottom of the thermostat so that water (small amount) can pass without it being open, this removes the need to "burp" the system.
Click to expand...

So this means I won't have to open anything up to burp it even after I get done replacing the hose and refilling?

Also, 5-90 do you have a picture of this done to one of yours?
 
Last edited:
Essentially correct. I do need to take a pic - it's just not high on my list right now...

What you do is drill two small (1/16" seems to be about best) holes in the thermostat flange, 180* apart, and about 1/8"-1/4" in from the edge - make sure they won't get covered by the gasket or the small recess the thermostat sits in.

When you install the thermostat, install it with one hole at the top and the other at the bottom. The top hole will pass air OUT, the bottom will pass water IN. This, in effect, makes the system constantly bleed itself. You'll want to run the system for about 5-10 minutes with the cap off so you can top it off, and then check it the next day (I was in a hurry when I typed that last time,) and that should solve the problem.

I do this with all my XJ's, and I don't have to do much more than what I just said every other year when I flush, drain, and refill the system. Works for me!

The "gold pin" is supposed to work as a self-bleeder - using only one hole. The pin is there to break up any bubble-locks that might happen, but it seems to work about half of the time. The advantage to two holes is that you don't have one hole handing traffic in both directions, and having "traffic jams" when you're not looking.

I'll have to see if I have a spare thermo lying about that I can drill out and snap to show everyone, but the idea is pretty simple. Think of a clock face - with a hole drilled right in the middle of the "12" and another right in the middle of the "6." Now, scale it down to thermostat size, and you're there.

5-90
 
5-90 said:
Essentially correct. I do need to take a pic - it's just not high on my list right now...

What you do is drill two small (1/16" seems to be about best) holes in the thermostat flange, 180* apart, and about 1/8"-1/4" in from the edge - make sure they won't get covered by the gasket or the small recess the thermostat sits in.

When you install the thermostat, install it with one hole at the top and the other at the bottom. The top hole will pass air OUT, the bottom will pass water IN. This, in effect, makes the system constantly bleed itself. You'll want to run the system for about 5-10 minutes with the cap off so you can top it off, and then check it the next day (I was in a hurry when I typed that last time,) and that should solve the problem.

I do this with all my XJ's, and I don't have to do much more than what I just said every other year when I flush, drain, and refill the system. Works for me!

The "gold pin" is supposed to work as a self-bleeder - using only one hole. The pin is there to break up any bubble-locks that might happen, but it seems to work about half of the time. The advantage to two holes is that you don't have one hole handing traffic in both directions, and having "traffic jams" when you're not looking.

I'll have to see if I have a spare thermo lying about that I can drill out and snap to show everyone, but the idea is pretty simple. Think of a clock face - with a hole drilled right in the middle of the "12" and another right in the middle of the "6." Now, scale it down to thermostat size, and you're there.

5-90
Click to expand...

Flippin sweet man, I thought that was what it sounded like but I'm glad you cleared it up. A pic would still help but I think I get the jest(sp?) of it.
Thanks again
Collin
 
Yeah. Like I said, it's on my list. #1054, I think...

I'm just taking a break now and eating (classes 0730-1800 TUE-FRI) before I put some cabinetry together for the smaller half.

I've got a few things I need to finish in the "little stuff" list. I think I saw a thermostat kicking around out in the shop somewhere - but I've got to work on that torque plate design, tear that 760x down that Brett sent me (if you knew what my last week-end was like...) and at least I'm done with "matrix algebra" for a little while.

5-90
 
5-90 said:
at least I'm done with "matrix algebra" for a little while.
Click to expand...

Funny, that's what I'm working on in geometry class right now. Anyway that's kinda off the topic, thanks again for the help though.
 
Thankyou
 
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