Coolant Level After Flush

[Sierra048]

I just flushed my Bride's Nissan Xterra's cooling system. Everything appears to be fine. Heater works good, not blowing cool air so I'm assuming that I purged all the air out of the system. Car runs nice and cool according to the gauge. After re-filling the system, I checked the level a couple of times and added as necessary to top-off until the reservoir was at the cold level and coolant was visible through the radiator cap. My concern: When I check the level now when cool, the level in the reservoir is approximately 60% to 70% full and I can't see any fluid in the radiator. I suctioned the AF from the reservoir until it was at the proper level again and added more AF to the radiator and it seems to make its way back to the the reservoir because the reservoir volume starts to rise again. Is this normal? Is it because it's a pressurized system? Help please!

 

[river_rat]

Reservoir has plenty, radiator is low...all when cool?
Looks like you need a new radiator cap.

 

[Sierra048]

River Rat,

I'm asking since I don't understand the mechanics of a pressurized cooling system: I can actually watch the reservoir level rise as I add coolant to the radiator when cool. How would a faulty radiator cap cause this? I really appreciate your help.

 

[JHZR2]

My 82 MB has no radiator cap on the radiator, just a pressurized overflow bottle. I had to replace a hose the other day going from this bottle to the radiator. So all the radiator contents came out. Refilled, burped all the air out, left a good amount over the max in the bottle, figuring that it would either come out or I'd remove it at a later time... Amazingly, after 500 miles, it is exactly at the right level.

Not sure why it dropped so far when I did this, perhaps there remained a bubble in the lower hose someplace? All the same, it ended up right for who knows why...

 

[river_rat]

Is the reservoir pressurized? If so, I don't know anything about those. If it's not, then the check valve in the cap isn't allowing coolant to get drawn back to the radiator on cooldown.

 

[The_Eric]

If the rad has a cap and the reservoir is not pressurized, then the first thing you want to do is get a new rad cap. After that, top the radiator off and drive it for a few days and re-check (My car takes about 2 weeks). Sometimes it takes several days to get all the air worked out of the system. If air is in the engine, then it will displace coolant. So when it works it's way out, the coolant level will drop as it fills in the voids the air once took up.

 

[Sierra048]

Thanks for the replies. I found some info on an Xterra forum that pretty much calmed my fears. It appears this is normal and nothing to be concerned about. Thanks again to all.

 

[dubie2003]

A good site to join would be thenewx.org since that covers all 05 and newer xterras.

Your engine bay is the same as the 2nd gen Frontier and Pathfinder since we all share the same VQ40 motor. Nissan are nitorious for trapping air in the heater core when flushing. Your best bet is to just overfill the resivour a little and run it till it drops, then repeat until you can not longer hear any running water coming from the dash.

SideNote: Not to cause fear or etc.... but if your Xterra is an auto, make sure you keep track on how the trans is doing, how the coolant looks under the cap and keep up on your trans d/fs. There has been some cases in which the internal ATF cooler line in the radiator cracks and causes the ATF and coolant to mix and the end result if not caught quickly is that you need a new/rebuilt trans, a new radiator and then a few flushes to clean out the motor. Nothing to really worry about but something to keep in the back of your mind when doing maintance.

 

[Sierra048]

Actually that's where I got the info I posted about. I've been a member there for a while. Yes, I am aware of the transmission issue. I did the bypass last November. Recently I did a poor man's flush on the transmission and hooked everything back to factory specs. Some thought the issue with the mixing of ATF and coolant was Nissan Matic J ATF. Others thought the radiators had weak brazing at the transmission connections. IDK? I refilled with Mobil 1 ATF and did a complete flush of the radiator. Short of replacing the radiator right now, I'll just keep my fingers crossed and take my chances. Thanks for the thoughts.