Contracted a case of P0128

[jbones]

As some know over the past year I've been dealing with PO306, as Opeth called it :

Just go right for the leak down test, after all you've posted its leading to a seized/ stuck valve. Everything you've done is exactly what I did, hate to say it but it might just be inevitable.

It's not an easy job either to remove the head, my GM bill was around $4k. Nearly all the head studs will snap off and exhaust manifold bolts too. If it is the head, might be easier to offload the truck and get into something else if you don't have the cash before that light starts to just stay on.

I ended up having to get the valve job done a few weeks back, yep, and 7 bolts broke, and by accident they poked the radiator (they replaced and eat the cost), truck has been running great. But, over the course of the few weeks I've had a few instances when the temp gauge wouldn't read, no engine light. Finally yesterday, light on, threw the P0128 low operating temp, and/or engine temp sensor, harness....
The thermostat looks easy, the location of the engine temp senor looks like a bitch of a location. I'll have the shop take a look, maybe they goofed, and will fix. If not, well hell I'm broke after that $3200 valve job.

 

[IllogicTC]

While it's normally suggested to do both thermostat and ECT at the same time, it's not actually necessary. It's very likely that its your thermostat, and you can probably get away with just replacing that (plus topping up the coolant you'll inevitably lose).

 

[jbones]

You mention topping off, and that brings to why is the coolant in Radiator brown looking, the reservoir is a nice dex-cool pink. It seemed the coolant in the radiator before the maintenance was still pink, now brown. Is this signs of other issues, or maybe they mixed coolant?

 

[IllogicTC]

You mention topping off, and that brings to why is the coolant in Radiator brown looking, the reservoir is a nice dex-cool pink. It seemed the coolant in the radiator before the maintenance was still pink, now brown. Is this signs of other issues, or maybe they mixed coolant?

Not sure how mixed coolant looks when it's still in liquid form, but I can tell you it gels up pretty nice, if you mean mixing Dex and non-Dex.

Dexcool is actually orange from the bottle, it fades to pink after a while. If you're having concerns of outside contaminants, there are known methods of testing. One such way would be to do an oil change and either examine the oil for water fouling, or send it to a lab such as Blackstone Labs for analysis. I'm sure there's a place to send coolant for analysis too, who knows? If you're leaning toward head gasket leading to coolant fouling, watch the coolant in the reservoir as the engine's running. Sometimes bubbles will show up in the reservoir (escaping exhaust gases I believe), then again I would expect it to force some of the directly-contaminated coolant to the bottle also.

Might just time for a coolant change. Dexcool is listed for 150,000 miles or 5 years, whichever comes first. 2014 marks 6 years on your vehicle, with 5 years being the generally-prescribed limit as the corrosion inhibitors in the Dexcool deteriorate over time. Some of it could be from a little excess corrosion (you're gonna have to do a drain to find out), or if you're not the first owner, someone putting in a lot more water than Dexcool to try saving a few dollars. Or it could be just absolutely completely normal or mostly normal.

Here is an interesting link: Dexcool Pictures and makes a good case for doing the cooling system up since you're draining some out via the thermostat anyway. I believe the T-stat is considered the removal plug for draining the block so you could just do a full flush.

 

[jbones]

Changed thermostat, all is good.