Hold on, how do we know the gauge or sender hasn't joined an obscure religious movement?Did you see the mechanical gauge read hot and cold too?
well, if the drive on the pump is broken, why would we still be getting sporadic cooling?
I'm suspicious of the coolant level and/or air someplace.
How this has suddenly happened is beyond me?
How did you decide the coolant level is ok?
Any recent work or added coolant?
My first guess is T-stat. They can suddenly fail and become erratic.
Second, as suggested earlier, is a hose collapsing (or getting an embolism (internal rupture between layers that fills with coolant and swells blocking off flow)).
Third could be a head gasket, but as your coolant level is normal that becomes more doubtful. But not so fast.
While I haven't actually seen a Detroit water pump, I know its like any other engine pump. Even if they leak they will still pump. The impeller can wear and reduce flow, but that never creates intermittent flow, it would just gradually slow down the flow. While not impossible, the impeller coming loose and working intermittently seems a stretch. I'm concerned about no heat in the front heater. Is it possible you have an air lock? You said you were climbing a grade. If there is any air in the system, air will rise to the highest point. So is it a flow problem, or an air problem? And if its an air problem, you have a leak somewhere, or a blown head gasket. You cant very well have a full coolant tank if there is air in the front heater.
IIRC there are numerous air bleeds on a Bus. If your lucky you maybe had some rouge air in the system that finally worked itself loose and is causing trouble. Whatever you do, remember these guys here have all said 190F is max on these big old dudes. Not 200F. You sure dont want to crack a head or pop a liner.
Quote from: artvonne on February 23, 2011, 09:57:20 PM QuoteThird could be a head gasket.as you said, doubtful. the symptoms just aren't there for this. Not to argue, but you have almost every symptom of a blown head gasket. Oil and coolant swapping is generally only seen the later stages of failure, or in complete failure. I only offered doubt because you said the coolant level is up. But then you said you have no front heat, thats it was cold. Is that because the heater is full of air? If its full of air, how can your level be correct? Have you bled the system of all air and re-checked you level? And if there is air in the system, where did it come from? That should be the first part of your diagnosis IMHO. A slipping pump wouldnt put air in the system unless you overheated past the boiling point and barfed coolant out the overflow. For the Detroit gurus out there, I am curious about the pump being able to slip intermitently. How can it only slip under high heat loads but not lower loads? I would think that once the key sheared it would just spin and that would be the end of it. Has this been seen before??
QuoteThird could be a head gasket.as you said, doubtful. the symptoms just aren't there for this.
Third could be a head gasket.