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Coolant gushes when burping 5.9. Bad tstat?

6K views 9 replies 5 participants last post by  godsdodgefreak 
#1 ·
Hey everybody, I've got a question for ya! I've got a '98 1500 5.9 4x4. A few years back I did the plenum repair and replaced my thermostat with a 180 degree one. All good there, aside from a heater that always gurgled and was sub-par. After reading up, I'm sure it was air from me not burping it well enough.

I had ghost leaks in my coolant for a while, and after fruitlessly trying to track it down, I broke down and added some of that silver solder leak stopper. Worked like a charm, but maybe this is contributing to my problem.

I just replaced my lower radiator hose (ah HA! found the leak! It only appeared in -0 weather), and immediately afterward the truck was running hot, like above 210 when it never goes above 180. And yes, I made sure coolant was full. Figured it needed a good burp, so preceded to get a no-spill funnel and run through it. Burps good, lots of air coming out, BUT, about the time the temp gauge hits 190-200 coolant begins GUSHING out of the funnel, like as fast as you could poor it in. I tried it a second time after it cooled off and filled back up to make sure it wasn't user error. Same thing.

I'm wondering if my 180 tstat is sticking because of the silver solder, or has gone bad altogether? Please tell me it's not a water pump...really don't want to go there.

Any advice is appreciated, thanks!!
 
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#5 · (Edited)
Off the top of my head, if the water is gushing like you say, then I'm certain the thermostat is opened, and the pump is working; if you're running at idle, the water should not gush out that bad though; that happens when the engine is ran at higher speed than idle; it provides good flow to dislodge any air bubbles.
At idle, there will be coolant flowing from the engine to the rad., through the opened thermostat, but it should not gush out the way you describe it.

What you have here, is 2 scenarios; one is the excessive gushing, and the other is higher than normal temp.
Before we jump to conclusions, we need to do a couple of tests.
1: with the engine at idle and fully warmed up,and the rad. cap installed, have a look inside the overflow bottle; (make sure there's water in there); you're looking for minute air bubbles. there are 2 sources of these bubbles: one is from air in the system, the other is from an exhaust leak. If the bubbles finally stop, then may be it was just air; if they continue, there's a possibility of an exhaust leak; put your nose close to the bottle; if you smell exhaust...that's not good.
The rad. cap will maintain about 15 psi., in the engine/rad/heater; any excess will be dumped in the overflow tank; this means that once everything has "settled" down and running nice, there should be very little if any "movements" in the overflow tank.
Just do one test at the time, don't panic yet;
Let us know what results you come up with...
You mentioned replacing the lower hose; make certain it is not pinched or kinked, which would not allow water out of the rad. fast enough and nowhere for the water from the pump, to go.
 
#8 ·
Well, I flushed the system to get all the gunk out, and I did get quite a bit! It didn't fix my issue though.

300m, when burping, the bubbles do stop by the time the truck gets to normal temp. I checked, and I don't smell any exhaust in the overflow or the radiator. However, the truck doesn't maintain temp, it keeps rising. I'm using a no leak funnel to burp, and the level in the funnel barely moves, aside from a few bubbles. At about 200 or so is when the fluid level rises pretty suddenly and starts gushing out.

I double checked all my hoses for leaks and kinks, looks good there.

A mechanic friend of mine is convinced that my radiator is plugged, and the fluid level is normal at that temp. I'm a bit skeptical since I couldn't see any corrosion when peaking in there, but that @$!# silver solder could be clogging it, and I got a good deal on a radiator so that's on it's way now. Anybody agree that a clogged radiator could be my issue? Other ideas? Thanks for the help guys!
 
#9 ·
You mention the fluid starts gushing out at about 200 degrees; that's about normal, as the thermostat just opened; it also says the pump is working.
Assuming the rad. is plugged or internally corroded, the lower hose should be cold; if it's warm it means there's some flow albeit not enough.
Given the age of your rad., that's a good possibility; everything else appears to work normally.
Before you remove the old rad, see if water comes out of the rad, as you remove the bottom hose.
Let us know the results of the rad. replacement.
Good luck.
 
#10 ·
Well, I got the new radiator installed, and it doesn't seem to have made a difference. I drove it twice today and both times it was still getting too hot.

300m, yes, coolant came out of both the radiator and the lower radiator hose when I pulled it. The radiator did seem the worse for wear: lots of gunk and the fins were bent in multiple places, but still no fix.

What next? Water pump and thermostat? Am I missing something?
 
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