Coolant system overhaul questions

[live2pull]

The Denali is in need of some attention to the cooling system.

I replaced my oil pan January of this year due to a leak. The previous owner did the gasket before me and the work I saw was shoddy at best. He also replaced the water pump......

I am not actively over heating, but, if I sit for an extended period of time >20 minutes idling the gauge starts creeping up. Also, I am having a weird engine stuttering issue that a coincides with a loss of ECT gauge functionality.

I plan on replacing all major components and ECT sensor, checking wiring and ECM grounds. Doing the block flush by removing the drain plugs to try to remove as much old coolant as possible. My main question is, should I do a chemical flush as well? Something similar to this product:

https://www.amazon.com/Prestone-AS1...em+cleaner&qid=1602113286&s=automotive&sr=1-2

I vaguely recall a friend of mine doing this and blowing a head gasket on his 02 Silverado. I have also heard of people using it with great results. I am leaning towards using it since I am doing the block flush as well.

Thoughts, opinions, facts, horror stories welcome.

Thanks

 

[OR VietVet]

Whether you do a chemical flush, IMO, would be determined by when it was last done, if ever, and the mileage on the engine. I would not do it if there is some uncertainty. I would still flush with a pressure hose and since you are draining it all and replacing components, the thermostat removal makes that all easier. If heater hoses are original, replace them and the tees. Radiator hoses too. Check for a water pump corrosive stain at the weep hole. How does the inside of the radiator look? I bet just like me, you don't know. That could be your source of the heating problem. You also could have a problem with the fan clutch. Lots to check. I hate assuming anything about a cooling system.

 

[live2pull]

Whether you do a chemical flush, IMO, would be determined by when it was last done, if ever, and the mileage on the engine. I would not do it if there is some uncertainty. I would still flush with a pressure hose and since you are draining it all and replacing components, the thermostat removal makes that all easier. If heater hoses are original, replace them and the tees. Radiator hoses too. Check for a water pump corrosive stain at the weep hole. How does the inside of the radiator look? I bet just like me, you don't know. That could be your source of the heating problem. You also could have a problem with the fan clutch. Lots to check. I hate assuming anything about a cooling system.

My parts replacement list:
Radiator upper lower hoses
Radiator
Heater core hoses and tees
Water pump and thermostat
Fan clutch
Overflow tank and cap
ECT sensor, connector if needed
And coolant of course

Other than the PO replacing the water pump, I have no other service history of the cooling system. The pump looks new, but red RTV has oozed out of the mating surfaces. This was much the case of the oil pan gasket replacement job, gasket and RTV. I am sure it is the case here. I agree with assuming anything about the cooling system. That is why replacing everything I can think of makes most sense to me. Especially, after what I saw doing the oil pan.

 

[OR VietVet]

I just did a full on inspection of my new to me 2005 Z71. Front pads thin and rear pads getting there. A/c belt shows a rusty color and the other belt looks newer but so what. Trans cooling line seepage. Plugs look ok but I want a base line for all of it.

My list from RA: Plugs, wires, air filter and am gonna clean the throttle bore and the MAF. All trans cooling lines. Thermostat, belts, tensioners and idler. Front and rear pads, rotors and rear park brake shoe kit. Changing out coolant, power steering fluid, transfer case, both diffs and doing a trans service. Brake fluid flush. I spent a little over $850 at RA, thankful for the 5% discount code. All AC Delco parts and fluids.

 

[live2pull]

Air filter and belt, thanks for reminding me!

That is a list! I've owned mine for 3 years and I've done; Suspension and brake overhaul, A/C compressor replacement, Oil pan (cracked), plus general maintenance, gas tank vent & purge solenoids and charcoal canister, and throttle body. Plus some interior work, seat covers, new dash bezel, driver arm rest, few other minor things. I think my PO thought he could tackle the issues mine has/had and made them worse then decided to unload it. I should have inspected more thoroughly because I believe he did a spit and polish and got rid of it. I was on my lunch break though and on the surface it was minor stuff easily fixed.

Still to do is; axel fluids, t case fluids, transmission fluid, Soft Brake lines (cracking), and of course the cooling system.

My biggest concern was the chemical flush and if the users on this forum would do it or not, or if i should absolutely not. At 180k, an unknown service history, and what I've seen while working on it, I am inclined to. Just thoroughly rinse out cooling system, which was the plan anyway.

 

[afpj]

If the previous owner used a bunch of RTV around the water pump gasket, and oozed internally and broke off, it could be interfering with function.

 

[alpha_omega]

If the previous owner used a bunch of RTV around the water pump gasket, and oozed internally and broke off, it could be interfering with function.

I second the PJ’s comment regarding the RTV. Just like the dirt and debris he removed out of a wound before closing it up, get all that old nasty shit out of the system so your new equipment doesn’t suffer a similar fate.
Good call on replacing the overflow cap. A commonly overlooked item by most people when replacing the water pump. As for the hoses, if you have the money to spare, go with something better than rubber (i.e. silicone). If you don’t plan to get that many miles out of the vehicle and/or don’t think you’ll get your moneys worth, then stock OEM will suffice.
As far as a chemical cleaner, trust in the Blue Devil. Hands down the best cleaner out there for radiators. Follow the instructions so you can make the most out of this cleaning, in order to bring your engine back to life again. Best of luck...


-Adam