- Jul 22, 2015
- 2,724
Well, as it turns out, my coolant leak at the lower hose where it joins the t-stat outlet - is actually coming from the bottom of the thermostat gasket. Was able to get a mirror on it and saw the telltale wetness on the thin edge of the gasket; verified it by feel.
Was solid for almost a year. Must've given way when I stressed the motor during my recent trip, running at +3000 RPM all day, as it never lost a drop of coolant until then (but loses it on every drive since then; I found the leak nearly immediately using a pressure tester two days ago)
So...I need to redo the gasket. Searched online & this site for gasket vs. RTV, etc. Nothing here on this specific issue, especially for the V8.
The one that's in the truck now came from Gates, along with the water pump. Or from Stant, as I had to purchase the 'right' (early model, with 'integrated housing') 5.3 t-stat when I did the WP last year. I forget 'whose' gasket I used, but it was one of the two.
(note: Stant's site doesn't show or mention the gasket; I know one came in the Gates kit, so I must've used that. Their site let me pick the 5.3L, then showed me only the 4.2L water pumps)
As an aside, the t-stat itself is just fine. I have no overheat / underheat issues at all. Just the loss of coolant; I was lucky I checked the level in the overflow bottle during my trip & since then.
Also, when I installed it last year, the bolts were torqued to the proper spec, per the manual (I think it's 17 ft/lb, just looking online tonight, but I know I did it to spec, whatever it is)
Options:
- Another gasket just like the 1st (paper, I think)
- Some other 'improved' gasket (I saw Fel-Pro rubber mentioned - ?)
- Regular gasket with gray RTV; let it set up overnight, then torque it down (found this on a pickup site, concerning a 5.3L truck)
- Skip the gasket altogether and RTV it up.
- Some other option I didn't mention.
What say the other experienced Gen III / 5.3L owners? (and if you had a t-stat leak, you go to front of the line w/ my 'thanks' for your answer)
Was solid for almost a year. Must've given way when I stressed the motor during my recent trip, running at +3000 RPM all day, as it never lost a drop of coolant until then (but loses it on every drive since then; I found the leak nearly immediately using a pressure tester two days ago)
So...I need to redo the gasket. Searched online & this site for gasket vs. RTV, etc. Nothing here on this specific issue, especially for the V8.
The one that's in the truck now came from Gates, along with the water pump. Or from Stant, as I had to purchase the 'right' (early model, with 'integrated housing') 5.3 t-stat when I did the WP last year. I forget 'whose' gasket I used, but it was one of the two.
(note: Stant's site doesn't show or mention the gasket; I know one came in the Gates kit, so I must've used that. Their site let me pick the 5.3L, then showed me only the 4.2L water pumps)
As an aside, the t-stat itself is just fine. I have no overheat / underheat issues at all. Just the loss of coolant; I was lucky I checked the level in the overflow bottle during my trip & since then.
Also, when I installed it last year, the bolts were torqued to the proper spec, per the manual (I think it's 17 ft/lb, just looking online tonight, but I know I did it to spec, whatever it is)
Options:
- Another gasket just like the 1st (paper, I think)
- Some other 'improved' gasket (I saw Fel-Pro rubber mentioned - ?)
- Regular gasket with gray RTV; let it set up overnight, then torque it down (found this on a pickup site, concerning a 5.3L truck)
- Skip the gasket altogether and RTV it up.
- Some other option I didn't mention.
What say the other experienced Gen III / 5.3L owners? (and if you had a t-stat leak, you go to front of the line w/ my 'thanks' for your answer)