backstory:
replaced rad, and water pump, hoses, t-stat (twice, 1st AB t-stat failed) about 5k miles ago.
situation:
after load of work to keep my disco II from overheating again, it was running great for about 6 months when last month while I was out of town on business, my wife took the truck on an errand...I never got the whole story, but she said it overheated, and she put another gallon of coolant in and made it home.
I then blead the system per RAVE
and topped off fluid (green EG)
symptoms:
while parked, the idle temps stay on the high side 203-205
if I attempt to drive is for more than a minute, they spike quickly to about 220 and I have to shut her off...
the cooland seems to be boiling over. fluid berbeling out of the overflow pipe at the filler neck.
noticed a hissing sound coming from cap...probably from the boiling pressure.
replaced the cap and reservoir tank, checked all the fittings for tightness and seal.
no change.
replaced the 6 mo old AB t-stat w/ a 180 britpart, and blead the system.
no change
no matter how many time I bleed the system, there always seems to be more air...waterfall won't go away despite having drained and refilled the system, and countless bleeding procedures.
I have a steep hill on my driveway, so I've been keeping it pointed uphill this whole time.
I got an exhaust gas tester from O'Reilly auto parts. started the truck, let it run for a few minutes...performed the test for a few minutes, but the fluid color never changed.
curious if there's anything else I should do before resigning myself for the head gasket job?
Thanks
thanks for your time and advice.
Scott

 

Diagnose some more instead of just resigning yourself to head gaskets.

Did you pressure test the cooling system. Easy way to find leaks. if you have a leak you aren't seeing, a pressure test usually reveals it in fine fashion. When you do it, pull the spark plugs and look for coolant in the cylinders?

 

X2, pressure test the system. You've done a bunch of work already, don't quit without doing this.

 

Yup. Pressure test it. Autozone has the tool for rent.

Take out the numbers 7 and 8 spark plugs to see if any coolant is getting into those chambers.

Good luck.

 

OK, thanks, guys!
I'll do the pressure test this weekend and report back how it all went.

 

when it's running, squeeze the hoses, open the bleeder, multiple times if you have too. I've had bleeds take an hour. I've also let the truck go higher than 220.
The temp is the temp at the sensor, NOT the stat. Just because it says 220, doesnt mean your stat is 195 yet, or all the air out of the stat for it to open all the way.
this is the mistake many people make hence why everyone constantly swaps out perfectly good thermostats and claim they know what they are doing when it comes to bleeding.

 

Sure, squeeze the hoses, but turn the engine off at 210, and squeeze the hoses until it opens at that temps which is more than adequate with a good thermostat. Going 220 plus is playing with fire unnecessarily IMO.

 

so, haven't done the pressure test yet, but this AM the fluid in the reservoir seemed way above cold full level.
I opened the cap and belches hisses and gouts of air came a rumbling up through the lower feed line.
I cracked the bleeder screw, held the res above the intake....mire hissing, and eventually nothing (first time for that). refilled the res and replaced the cap, left the bleeder off, and cranked the engine till sweet green came out of the bleeder. replaced bleeder turned the engine off. waited a while, rebleed without resulting air.
started the engine, intermittingly cracked the bleeder to see if the air had built up....a few small pockets perhaps.
the temps holding steady at 183, but the level in the res seemed dangerously low, so I cracked the cap, and put a bit more coolant in.
I drove around the block a few times and reparked in the driveway. while the temps never rose above 194, the level in the res seemed dangerously low again and the cap was visibly releasing steam and pressure from the internal seal, and the overflow spout was dripping about once every second or two and the hoses were all super tight.
more air in the system??
I know I'm now LR master, but I've never had this much trouble bleeding air out of the system, perhaps I've just been lucky..but I suspect (without empirical evidence) that something else is amiss.
if there were a leak in the system allowing exhaust gasses in, the system wouldn't hold temps at idle (I shouldn't think).
if there was a leak in the system, it wouldn't hold pressure in the res after sitting all night.
I still plan to do the pressure test, but I don't expect it to show anything new...but who knows.
otherwise, it runs smoothly and has plenty of power.
more to follow after pressure testing and further bleeding.
S

 

It is very possible you had a bubble somewhere and it burped out finally. Hopefully, it passes the pressure test and you are good to go.

 

Went through this for a while after a bleeder T screw failure, it can take more than a few attempts to get air out. After getting warm the system will release some air and draw coolant in, seems scary but in my case after a week everything is stable again.