I noticed my coolant was near the fill line a few weeks ago. I topped it off, seemed fine.

Now I see that it is down maybe an inch or so. Could this be because it is a cold engine? Or temperature?

I did a radiator flush maybe 6 months ago, could it be the radiator drain? I tightened it the best i could but does it have to be super tight? what tool do you use to do this?

Thanks

 

It could possibly be that there were tiny air bubbles leftover from the rad flush that have been working themselves out.

I'd just keep an eye on it for the next week or so. Since you haven't said you see it on the ground if its leaking its a slow leak.

Or its getting consumed.

 

With the age of your XJ after checking all the hose clamps and nothing looks to be leaking, there is another item to check. After changing my starter last month on my 96, we noticed wet areas around the starter and after searching, we found the heater control valve was slowly leaking. The control valve is the 4-way plastic unit with a vaccum hose coming from it. Its the switch that dirverts coolant to your heater core located on the passenger side of the fire wall. My valve cracked from age, and my coolent bottle was losing about a inch a month.

 

An inch isn't much and may just be within normal variations on the bottle.

There is no heater control valve on a 1999. They went away years earlier.

If you continue to see a drop in the reservoir, you may have a small leak in the seam of the radiator. This is very common with older OEM radiators. My radiator on my 1999 failed in this manner after 10 years / 130k.

The leak starts out very small at first.....Look at the seams closely with a good light from underneath. And be sure to check the weep hole on the water pump while you are under there. And of course, ensure hose condition and tightness. Real old radiator caps can allow some fluid to escape as well. They are only about $5.00 and are often overlooked.

 

A buddie of mine has an adaptor for radiator caps. The adaptor has a bicycle pump like thing attached to it with a pressure gauge. You replace this with the cap and start to pump the pump. When the pressure gauge gets to a certain level you pause and wait while watching the gauge. If it drops, then you've got a leak somewhere.

This is a really nice way to check into coolant leaks as you can poke around while the system has positive pressure and look for the leaking coolant. With the motor off.

I'm not sure how much this little tool cost him, but it may be worth checking into. If its cheap enough it'd be nice to have, in my opinion, but it may also be a rentable tool or something.

 

did you have to replace the radiator, TJ? Or re-weld it?

 

damn, I think that's what is happening. I see coolant coming from under the radiator. Mines right around 117k. Might try a stop leak product

 

got bar's stop leak, gonna try that in a few hours. Ill let you guys know how that turns out

 

Not a huge fan of stop leak products. It might work on very small leaks, but can also contribute to the clogging of your heater core.

If the leak is coming from the seam on the radiator, stop leak is only temporary and that seam is going to blow some day when you are a long ways from home, (murphy's law) and then you'll have an overheat, possibly a blown head gasket, and need a tow truck.

Replace the radiator. They are NOT expensive.

 

I was noticing about an inch of coolant loss (looking at the overflow with engine cold) per month. I just found out I have a leaky waterpump.