89 Asto 4.3 running hot

89 Asto 4.3 running hot

Postby sturoc [OP] » July 24th 2011, 5:54pm

Did a water pump replacement 2 yrs ago
Flushed the system run 80/20 coolant water mix
Temps were normal for 1 1/2 Now all of the sudden she's running hot over 200 and up tot 240.
I changed the Oil and antifreeze last week and took along ride up in the Mtns and uphill she goes way over 220 but cools down to say 190 200 on the long downhills.
The Engine runs fine no smoking or leaks. Even when very hot it has good power. Fan is fine too.
Any ideas ?

PS. how does one reach that dang heater core hose it's so deeply tucked away I can't get my arm in there to change it out !
'89 Astro Van cargo, 4.3 tbi, Auto trans rwd
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Re: 89 Asto 4.3 running hot

Postby Leeann_93 » July 24th 2011, 7:56pm

You should be at a 60/40 coolant water mix. Pure coolant doesn't cool as well as mixed, and the more mixed, the better.

Next question, though, is did you check the temps with an infrared thermometer on the upper rad hose? The gauges are known to be inaccurate and the sending unit for the gauge does go bad.

When's the last time you washed off the radiator and condenser - as in, loosened the mounts so you could wash in between?

Also, have you ever replaced the radiator cap?

And another question: (go out to the van when it's cool) Can you freely spin the fan? If so, your fan clutch is toast.

Sorry, can't help you on the heater core....
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Re: 89 Asto 4.3 running hot

Postby sturoc [OP] » July 25th 2011, 12:35am

Coolant is probably good as the problem occurring prior to the flush and new coolant going in as well.
Cap not been replaced ,
Fan is good.
Infrared thermometer I do not have one of those.BUT you bring up an interesting point about washing off the Rad and condenser asI live on adirt road Use the van to go up in the mtns further -on dirt roads.
Will ck that out
Lastly is these do not work, may do the sensor replacement. But it is only1 yr old.
thanks for some direction here.
'89 Astro Van cargo, 4.3 tbi, Auto trans rwd
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Re: 89 Asto 4.3 running hot

Postby Shad0wXCalibur » August 31st 2011, 7:39am

You could have a sticking thermostat if you've never replaced that. Could also be the 80/20 coolant/water mix. That's too little water. The water is mostly what carrys away the heat in your engine. I run 70/30 water/coolant because it gets so hot down here, the clutch fan has trouble keeping up idling and can start creeping past 210F with 50/50. The coldest it ever gets here is maybe mid-teens so 30% coolant is still enough for me to keep my engine from freezing up.
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