96 Blazer overheating and then....

[7T9Shark]

OK, here are the results - After replacing the thermostat (twice, the first replacement wouldn't open all the way) I also removed and inspected the water pump - looks good; I removed the radiator and drained a bunch of crud out of the inlet.

So, will take the radiator in to the shop tomorrow and have them assess whether or not it can be rejuvinated. In 50 years of car ownership I've NEVER had a plugged radiator. That's why I was looking at every other possibility. Another learning expierience.......

[7T9Shark]

OK everyone, here are the results. Today I removed and inspected the water pump - Looks good, bearing is tight and spins freely. I also installed a second thermostat. The replacement I installed last week just wouldn't open all the way like it's supposed to at temp.

Here's the final assessment. The radiator appears to be the culprit. When removing it, I poured a bunch of cruddy swill out of the inlet pipe. Will take it to a shop tomorrow and see if they can boil it out, as it doesn't leak and looks good. I'll see what they say......

Thanks to all for your suggestions.

AJ

[viggy58]

just do a full coolant system flush. the rad is prob fine, just needs new coolant.

[7T9Shark]

Spoke to soon. Filled the system, ran it for awhile to purge the air and then let it sit overnight. Next day checked level and all looked fine. Took it out and same thing. It starts out heating up normally on the guage, and then it takes off. When I got back to the garage the heater was blowing cold again, and the upper radiator hose was barely warm. The thermostat housing on the intake manifold was hot.

This is frustrating given the fact that I replaced the thermostat and radiator, as well as checked the water pump on the work bench and it spun freely.

It's beginning to look like I might have an internal blockage within the block or heads.

The oil checks out fine with no "mayonnaise" build up or evidence of coolant migration. I'll probably take it to a shop next week and let them take over.

A major bummer......

[534BC]

Here's 2 things to do if you can:

Do a combustion gas test.
Purge vapor out at the 2 bleeders. (can't tell if you've done this)

To me the venture is very difficult to get vapor out of the system (even with the bleeders)

EDIT sorry I thought I was in a chevy venture thread still. (no bleeders yes.)

[7T9Shark]

OK the bottom line is that the THIRD thermostat did the job. Engine warms up and runs at normal temp. now.

Go figure........