1999 Chevy Subburban LT 4x4 that has been an amazing vehicle (200k miles) but I fear I may have damaged her, let me explain.
I have known for about the last 10k miles that I appear to have a VERY SMALL intake gasket leak. So small in fact that you can only tell when idling in gear (say at a stop light) and even then the untrained ear (like my wife) might not be able to tell. It also only throws a code (P0300) every so often.
I tell you this for reasons that will be clear in a moment (and yes I plan to replace the intake gasket soon).
About 6 weeks ago, in 50 degree weather I replaced my thermostat and did a coolant flush along with an oil change. All has been fine even in freezing weather until today when the temperature was sub zero for the first time this season.
I went out and started the truck while getting ready for work and when I came out 20 minutes later the temp needle was pegged and cold air from vents. I quickly shut the truck down knowing it was most likely not enough antifreeze in radiator
After the truck cooled off I drove her 20 feet to the garage warmed to 45-50 and a few hours later checked the coolant. It was then that I noticed two things:
While I normally ALWAYS use pure undiluted coolant, I mistakenly used 50/50 diluted that I then diluted to 25/75 (thinking I was using undiluted 6 weeks ago during flush).
The system was no longer full (probably 85%) which means that the small intake leak over the last 6 weeks had further weakened my anti-freeze protection.
Inspection showed no loss of fluid other than the overflow drain during the overheating so I am hopeful that I did not crack the block. After draining and filling properly with right amount of anti-freeze the truck started right up and sounded no different than ever.
Does the burb have freeze plugs in the block? If so how can I tell if they “popped”
I did drive 50 miles in -4 degree weather and the only thing I noticed was while my front heat worked great, the rear was blowing cool no matter the setting.
So I ask you, what damage might I have caused and what would you check/do to the truck to determine if there is any issue and to get that rear heat back?