After flushing and refilling the radiator, I ran it with the cap open for a while but am afraid not long enough. Today after about 5 miles noticed at idle it would rev up to about 1200rpm then drop down then repeat and there was massive leaking from the water pump seal area. Managed to get home without overheating. Expansion tank/resevoir still full, no visible level in radiator, and gurgling from block. I'm assuming too much air in the system...???

Question: Could not bleeding the cooling system cause water pump failure? Or, what's a more likely cause? Scale getting knocked loose? Already bought a new water pump, just want to be certain about what happened so I don't do it again.

 

I don't think a air pocket caused the leak. It was probably just time for you water pump to let go. At 202000 miles it would not surprise me if it was the original water pump.

 

you could always try a new gasket and make sure if you do bleed it off the should be a bleed off plug around the thermostat housing

 

Sounds like the pump was ready to go. Install new one. and call it good. air pockets can usually work themselves out.

 

The flush probably cleared out whatever was in the pump seals and it let go.

 

Yeah, I suppose it's to be expected with 200k+. Thanks for the piece of mind though...sort of takes the blame off of me a little bit.


...stupid water pump, can't even last 250,000 miles.

 

Problem solved and answers found! After installing a new water pump, I paid really close attention when filling/bleeding the system. With the truck on ramps and the engine running, once the thermostat actually opened, the engine started surging again and I noticed the level in the radiator pulsing with the surges. The first time this happened I had the radiator cap on, the second time it was off and I was watching it. Once it began to surge the radiator gushed out coolant in surges. I tried squeezing the hoses to help burp the air out but it kept surging. Finally I got frustrated with the splashing coolant mess and shut it off. Only then did a really big burp let out and the level of the radiator dropped a lot. After that, problem solved; topped off the radiator, no more surging, cool running, all good.

What I learned: If you've just refilled your cooling system, don't put the cap on tightly until you're sure all the air is bled out. The surging within a closed system overwhelmed the bleed-off hose into the reservoir and put lots of pressure on the water pump gasket and seal causing it to fail in my case.

 

Often lowering the idle a touch with eliminate the loping idle. Could be the TPS, but I doubt it in this case as it would be very coincedental.