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Tony the Liger
November 7th, 2017, 15:18
I just installed a new water pump, fan clutch, thermostat and radiator cap. When I wrapped things up and topped off the coolant, I started it up and while idling, coolant began to overflow from the radiator fill spout (with the cap on). At this time, the overflow tank was full right up to the FULL line. I let it run until it stopped overflowing from the radiator spout, and over the next few days I didn't have any issues. No leaks and the temp has stayed cool each time I've driven it since completing the work.

Fast forward to last night. I drove it around for a while, and when I got home and shut it off, I heard a drip. Looked around and realized it was burping up a little bit of coolant from the radiator spout again (pouring straight onto the ground beneath that point). The overflow tank was still sitting at just below FULL. Didn't mess with it any more last night.

Checked on it when I got home from work a little while ago. The overflow tank is now almost completely empty.

A. Shouldn't the first round of overflowing coolant have flowed into the overflow tank, instead of pouring out of the radiator spout?

B. Why would it have gone three or four days without doing that, then burp up a little bit from the same spot?

Any thoughts? Clogged hose from the radiator to the tank, or is this indicative of a different/bigger issue?

blakews2217
November 7th, 2017, 17:17
I just installed a new water pump, fan clutch, thermostat and radiator cap. When I wrapped things up and topped off the coolant, I started it up and while idling, coolant began to overflow from the radiator fill spout (with the cap on). At this time, the overflow tank was full right up to the FULL line. I let it run until it stopped overflowing from the radiator spout, and over the next few days I didn't have any issues. No leaks and the temp has stayed cool each time I've driven it since completing the work.



Fast forward to last night. I drove it around for a while, and when I got home and shut it off, I heard a drip. Looked around and realized it was burping up a little bit of coolant from the radiator spout again (pouring straight onto the ground beneath that point). The overflow tank was still sitting at just below FULL. Didn't mess with it any more last night.



Checked on it when I got home from work a little while ago. The overflow tank is now almost completely empty.



A. Shouldn't the first round of overflowing coolant have flowed into the overflow tank, instead of pouring out of the radiator spout?



B. Why would it have gone three or four days without doing that, then burp up a little bit from the same spot?



Any thoughts? Clogged hose from the radiator to the tank, or is this indicative of a different/bigger issue?



Rad cap seal and or split overflow hose. Also use a hose clamp on the spout to the overflow.


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four_shot
November 7th, 2017, 18:54
Rad cap seal and or split overflow hose. Also use a hose clamp on the spout to the overflow.

X2

If the outer seal of the rad cap doesn't seal to the rad neck, it will not draw coolant back in during the cool down portion of the engine's heat cycle. If the rad cap is defective, it may be intermittently leaking dependent on temp. Same with the overflow hose.

Tony the Liger
November 7th, 2017, 19:37
I'll check on both. Thanks for the tips.

My brother-in-law (XJ guy for 20+ years now) said it might be as simple as having not properly "burped" the air out of the system when refilling it with coolant, and that the splashing/overflow was a result of pockets of air being forced out. Sound legit?

RCP Phx
November 8th, 2017, 03:39
I'll check on both. Thanks for the tips.

My brother-in-law (XJ guy for 20+ years now) said it might be as simple as having not properly "burped" the air out of the system when refilling it with coolant, and that the splashing/overflow was a result of pockets of air being forced out. Sound legit?

Nope!

four_shot
November 8th, 2017, 14:13
Any air forced out should be routed to the overflow tank. Nothing should be coming out at the cap.

ParadiseXJ
November 8th, 2017, 20:48
Bad cap. Get a dealer cap or at least a good cap rated for 16 psi.

jonb8
November 9th, 2017, 04:43
Blow through the hose that goes to the overflow, I've seen a lot of them clogged up and the fluid can't return even with a new cap.

Tony the Liger
November 11th, 2017, 07:49
The cap I'm using is a brand new OEM. Yesterday I checked the hose that runs to the reservoir, and it isn't clogged. I added 50/50 to the reservoir FULL line, then started it up with the radiator cap off and the heat on full blast. After running for a few minutes, the coolant that was visible in the radiator began to rise and fall, eventually rising to the point that it overflowed again. It continued to do this until the temp gauge hit 198 or so, then the coolant (in the radiator) settled back down to a normal level. I let it run a little while longer; no temp changes, and no overflow repeats. The levels in the overflow reservoir never changed.

Didn't try again with the cap on. Thoughts?

techno1154
November 11th, 2017, 08:33
The cap I'm using is a brand new OEM. Yesterday I checked the hose that runs to the reservoir, and it isn't clogged. I added 50/50 to the reservoir FULL line, then started it up with the radiator cap off and the heat on full blast. After running for a few minutes, the coolant that was visible in the radiator began to rise and fall, eventually rising to the point that it overflowed again. It continued to do this until the temp gauge hit 198 or so, then the coolant (in the radiator) settled back down to a normal level. I let it run a little while longer; no temp changes, and no overflow repeats. The levels in the overflow reservoir never changed.

Didn't try again with the cap on. Thoughts?


I do not know anything about burping the cooling system in my 1996 XJ or the 1994 XJ I had at one time. Open cooling system are/should be self burping.

Verify the replacement water pump is correct, i.e. the impeller is of the correct rotation and not rotating in the opposite direction. Thermostat,...I use only those purchased from the dealer. Some here have used other brands that performs well. The cap should be rated at the correct pressure and fit well. Do a visual inspection of the outer sealing ring (both sealing rings) and the radiator lip for anomalies. Repair or replace as needed.

When I service the cooling system on my XJ, I employ no special procedures. I simply fill the radiator then install the radiator cap making sure it is seating properly and is tight. Then I fill the coolant recovery bottle all the way up past the full mark, within an inch or two of the very top of the bottle which is about 2 quarts. I then run the engine until it reaches operating temperature then shut it down and leave it to cool for a few hours. If the cooling system is properly sealed, at least a quart of coolant would/should be withdrawn from the recovery bottle into the radiator as it cool down. I do not take the radiator cap off when the engine is running nor do I remove it when the engine is hot.
I my 17 years of owning XJ's I have never burped them nor do I have problem of air being in the system.