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Lt1_8U · 04-22-2013, 06:37 AM

I have a 1990 gmc sierra with a 5.7 tbi and a 5 speed. A few days ago while going to pick up my gun it started overheating.

I changed the thermostat and nothing
No leaking out of my pump
I flushed the system
I changed the coolant cap
I Noticed that when I give it throttle the upper hose flexes like it is compressing.
My cat isn't clogged

It will normally climb to temp but then it will slowly go to around 230-245 than instantly drop 35-40 degrees in a few seconds. I'm going to purchase a digital thermometer to see what temp it reads.

Thanks guys!

04-22-2013, 06:37 AM	#1
Lt1_8U Join Date: Sep 2006 Location: north jersey Posts: 1,680 iTrader: (3)	Overheating issue I have a 1990 gmc sierra with a 5.7 tbi and a 5 speed. A few days ago while going to pick up my gun it started overheating. I changed the thermostat and nothing No leaking out of my pump I flushed the system I changed the coolant cap I Noticed that when I give it throttle the upper hose flexes like it is compressing. My cat isn't clogged It will normally climb to temp but then it will slowly go to around 230-245 than instantly drop 35-40 degrees in a few seconds. I'm going to purchase a digital thermometer to see what temp it reads. Thanks guys!