Thermostat Opening Late?

[Schurkey]

WHAT IS YOUR ANTIFREEZE CONCENTRATION? WHAT PRESSURE IS YOUR RAD CAP RATED FOR? Does the rad cap actually hold that pressure?

Your coolant shouldn't boil under pressure from the rad cap until it's at ~260 degrees F. If you're not using enough anti-freeze (which is also an anti-boil) the coolant might boil at a substantially-lower temperature.

If the rad cap doesn't hold (enough) pressure, the boiling temp is even lower.

50/50 antifreeze/water boils at 238 degrees F, with a 15-psi pressure cap on the rad, it boils at about 260 degrees. Is your engine getting that hot after shut-down?

 

[97C1500TJ]

So I spent several hours and three test drives to completely flush the block. There had to have been a slight blockage somewhere because even with straight water, it wasn’t boiling in the upper hose. This was my old coolant concentration.

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[97C1500TJ]

My rad cap is rated for 16 psi.

 

[Schurkey]

Does that 16-psi cap actually hold pressure?

Pull the block drain plugs to fully-remove the flush water.

If this is a V-6 or small-block, the knock sensor is the plug on the right side of the block. The left-side plug would be a steel/iron plug with a 9/16 hex. Not uncommon for the bottom of the block to be packed-full of scale, rust, debris. You might have to poke the scuzz with a Phillips screwdriver to get the contaminated flush water to drain.

Put the knock sensor back in at the specified torque, and with sealant on the threads. I generally replace the iron plugs with brass plugs, or--on vehicles I own--with brass draincocks.

Use the capacites section of the owner's manual to figure out how much coolant your vehicle takes. Add a little less than half that much anti-freeze to the engine before putting any water in. Top off with water as required. (Save some of the anti-freeze for the overflow tank.)

 

[454cid]

-10f is not a 50/50 mix, that looks like you didn't have the gauge full enough.

 

[97C1500TJ]

-10f is not a 50/50 mix, that have looks like you didnt have it full enough.

Right. I for some reason didn’t even think to check the concentration first. Although there was definitely a blockage somewhere in there at least slowing the flow down because I washed mud out for quite some time.

 

[97C1500TJ]

I’ll continue to monitor it for the next few days but this is definitely a major improvement. Also replaced a broken temp sending unit that was broke off causing the CEL to come on.

 

[El Tigre]

What is the attraction for 195 stats?
180's work fine ,and under-hood plastic/rubber will last longer

 

[Schurkey]

The OEM computer tune was developed around a 195 'stat. The 195 provides somewhat less engine wear, better heater output, slightly better fuel economy and reduced emissions. A 195 'stat makes the radiator more efficient because there's a greater difference between the temperature of the engine coolant, and ambient air.

I don't see the engine thermostat making a big difference in the service life of under-hood rubber/plastic, as thermostat temperature has little effect on exhaust gas temperature and therefore exhaust manifold/intake manifold exhaust crossover temperature which will affect under-hood temps.

A 180 isn't bad. I have no use for 160 thermostats in an automobile/light truck, although they seem to be recommended for my boat (and I've not done any experimentation with hotter 'stats.)

 

[El Tigre]

Then 195 will be the coolest it will ever be. GM's interests in lowest possible emissions when new don't dovetail with my performance interests to begin with. Higher the temps the higher the tendency toward detonation. Plus that much closer to boil over as stats get lazy ,caps don't maintain as much pressure ,etc. Add weakened coolant along with a hot summer day ,and overheating suddenly becomes a real possibility.