Mine definitely has rushing coolant right at the top under the plug. You might try revving it too, to make the pump push coolant faster, and maybe get more bubbles out.

 

Yep. the stat does not make air (usually a leaky stat gasket will be very obvious), and the hole lets you be a real gas passer (anesthesiologist humor, my bother is one, and a family physician, and an aviation medical examiner and has his multi engine ticket).

Seems like the throttle body heat circuit would have flow all the time. Cold is when it is needed most. Maybe bubble is so big that it is being impacted as well.

One poster today mentioned he added coolant while some one revved up engine somewhat, the increased water pump flow and pressure moved the bubble out.

See pix of a hose attachment, I was flushing, but I would suppose you could pour coolant in thru an elevated funnel, say on a step ladder, and water seeks its own level. But problem is also that the cooling system is not all one series connection. There are parallel areas, like the halves of the engine, the heater circuit, the throttle plate heater circuit, etc. I guess you could also have a short hose, run the engine, bubbles and coolant come out, and keep pouring coolant into the reserve tank. Because it is so cold where you are, might have to block 50% of radiator to make stat open fully.

 

Revving the engine to 200-2500 for 15-30 seconds is what it took for mine to purge air. I started with a cold engine (and therefore no heat in the heater box). When the air purged itself the temp of the air from the vents inside the vehicle was dramatically warmer in seconds.

 

Another trip to town and more data. I tried revving and purging last night with little success.

Way to town this AM temp gauge went all the way above 'normal' line and stayed there way too long for comfort. Then dropped down to 9:00. Did this a few more times with the oscillations reducing but still alarmingly high. Only does it under load. While at idle it stays pretty steady. After sitting out in the parking lot for three hours, drove home and had similar results except the first swing of the needle is getting higher and higher...almost touching red now. By the time I get home the oscillations have basically stopped.

At this point it has to be the t-stat. Obviously there is air in the system, I still hear it gurgling behind the dash. Maybe this is just a weird coincidence that both problems arose at the same time.

I'm off to get the new t-stat now and will report back later. I hate to pull it now and deal with the mess while I'm waiting for the hoses to get here then do it all over again but I would like to have the Rover for the next few days as a major winter storm is about to hit us and dump a ton of snow. That's basically what I bought this thing for so sitting in the shop at this time is hard to swallow. Why didn't they just put a drain valve or plug for the coolant? Doesn't every other vehicle on the planet have one?!?!

 

Perhaps the mess could be less if you loosen lower hose and drain about a gallon into a bucket, to get coolant level below the stat, before opening up. Siphon pump out top hole?

 

I've saved a lot of messy hassle by using a fluid pump or siphon from the radiator to empty coolant containers. This allowed me to reuse the coolant too. If you drain it from the hose it puts stress on it, makes a mess, and any coolant you manage to collect will likely have dirt in it.

 

Thanks guys. I just got back from the parts store and after talking with them they thought I probably had air in the system. Obviously I do because I can hear it. I picked up a new stat and a couple of gaskets anyway.

So after getting home I gave it another go with burping. This time I put a towel in front of the rad and staked the throttle to run about 2K RPM. Ran this way for a long, long time. Finally coolant started coming out of rad (small cap) and bubbling some. But the t-stat would only stay open for a few seconds.

I could put my hand on the upper hose when the t-stat was open and feel what I believe to be steam bubbles rocking and shaking the hose. It's actually quite a lot of vibration. So I squeezed the hose to try and work this out but it would only last a few seconds. Anyway, carried on with this routine for quite some time. Hard to tell if I'm making any progress.

I topped everything off again and sealed it up after about 30-40 min of this routine and took it for a spin. Within a block the temp gauge was again on the rise. I can also still hear bubbles behind the dash. It didn't sound quite as bad this time though and the gauge only went to about 10:00.

I'm going to let it cool down again completely and try burping again from step one. If that doesn't work, I'll pull the t-stat and put the new one in. In fact, I think I will test the new one right now. Can a waterpump be intermittent? Seems unlikely but I'm scratching my head a bit on this one...

 

One new stat, go ahead and drill a 1/8 inch hole in the flange to be sure air will pass by. Water pumps can have missing impeller blades, or impeller can slip on shaft, here's pix of what they look like inside. If you hear the bubbles, it is pumping. If belt is on wrong ran won't run counter clockwise facing engine from the bumper.

 

Was looking at the RAVE while waiting for everything to cool and trying to understand the throttle body heater. The heated coolant comes from the intake manifold, it passes through the TB then returns to the top of the rad. If this is heated water from the engine block and in front of the t-stat, how does the coolant get replenshed? It has to loop somehow. And of course it is driven from the WP. I would think this to be circulating all the time not just when the t-stat is open.

I can look into the small hole and see where the hoses dump into the rad but nothing is happening there until the t-stat opens. I swear when I first got this thing I could look in tere and see fluid moving all the time. I think Eric's post confirms that. Something just doesn't seem right.

I know you can 'what-if' something to death but if the WP impeller is slipping on the shaft that could explain some of this. It may take a while to 'warm-up' before operating. It may spin freely for a while then friction-weld itself back together enough to work for a while. Since my temps are so cold it's able to sort of function like this. I don't know...just a random thought.

 

Just noticed they gave me a 192 stat and that's not what I want. I want a 180. So I'm not going through all this hassle and not putting the correct stat in.

Looks like the F250 will be braving the elements tomorrow. It's been so spoiled in the garage all winter!

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