Woke up this morning to find a nice puddle of coolant under the truck. Seems that it’s seeping between the engine block and the cylinder head. Could it be the gasket? What would you do first to try and identify the cause? Attached a few pics but may not be as clear to see. In any case appreciate feedback.
thanks. Dan

 

This also odd, but is it possible that the weather (freezing temps) affected the seal in addition to it being worn out? I’m in Florida and last 4 days we were in the low 30. Right now warm mid to high 60. No leak whatsoever this afternoon.
I checked the spark plugs as well so see if anything got there but they are dry. So confusing.
Either way new deals will be replaced but this got me baffled.

 

maybe the rear steam crossover pipe is leaking. or that is oil and the oil pressure sender is leaking

 

Your pics show yellow fluid (on the ac line too), what color coolant are you using?

 

 

Isn't the proper coolant color for the 05 H2 Dexcool pink, like for all Hummers, or did that change at some point?

Are you using Prestone or some other green stuff?
When is the last time you flushed your cooling system?

Not saying this is the cause, but still. That is a lot of spilled coolant, pointing to a catastrophic failure. You can take it into a shop, or use a UV-dye tracer, black light, and anti-UV (orange) goggles to figure out where it is coming from. First you wash that area, then you pressurize the system and watch for a leak with the black light. The area will glow.

I certainly would not keep driving it before repairs. You do not know if something is about to burst open.

 

I use the universal coolant which is yellowish in color. I put that in well over a year ago when I worked on the water pump, hoses, etc.
Is this coolant going to harm the engine? I hope not as I was told this is good to use.

also, it still appears to leak from between the engine block and the cylinder head. I checked everywhere I could for other sources of the leak and I can’t find anything.

this engine is the second engine with well over 200k miles on this one. Prior engine was also replaced after 200k miles (long story short the mechanic screwed up and they had to replace it). Currently at 436k miles.

either way, I ordered the gaskets, new head bolts and a few other items. I guess I will find out the cause as soon as I get to remove everything which will be fun. I should have done that when I did the knock sensors but who knew then.

thanks for the feedback. I will give an update and some pics very soon.

 

yeah truck is parked until its fixed I sure don’t want any other major problems to arise from this leak.

I posted a pic of the coolant I use. As far as I was told this was ok to use on any car, light truck and works with any type of coolant.

 

are you referring to the cylinder head coolant steam vent port plate plug by any chance? Those located at the back of the engine? I replaced the front cross over line in the past. I actually ordered those plugs as well with new seals. Thanks.

 

also thanks for the link. Got me watching a bunch of videos. New coolant is yellowish.