1999 Burb 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 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:

1. 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).

2. 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?

 

wow that's some story, hopefully all is good, sorry i can't be of any assistance, but tagging along to see the outcome

 

as long as there is no knocking you probably will be alright. Sounds like the head gaskets made it ok. If the frost plug blew out there would be a massive leak. Usually, the don't blow out on a overheat condition as the coolant will exit the reservoir. If there is a concern that they may be leaking from the coolant freezing, do a coolant pressure test.


the no heat in the rear is probably from air trapped in the system.