Alex71

I am new to the forum but based on the topics and information i have found on the forum this seams like a good place to get some answers to my problems. My z71 Tahoe is loosing coolant with no signs of it leaking. I have been trying to determine what could be the problem.

What i have done so far:

- Replaced water pump and thermostat. Was leaking from thermostat housing, replaced again and used rtv, no signs of leaking now.

- Pulled valve covers to determine no contamination in oil. Also pulled rocker arms and determined it does not have castec heads.

- Compression test came reviled i didn't have zero or low compression on any cylinders.

- Put UV tracer dye into the coolant to look for leaks at night with UV light. No signs on the exhaust pipe or external.

I noticed that my low coolant light will come on some times with plenty of coolant in the overflow tank. I will check it and there is plenty in there. It will do this off and on until i see that it is low enough to put some in. Over 3000 miles it will leak down an inch or 2 in the overflow bottle or require about 1/4 to 1/2 gallon of coolant.

I am in the process of installed a new transmission and rebuilding the front end so i have been quite frustrated with the money i am putting into the vehicle with only 125,000 miles. If anyone has any other ideas of what else to do.

grey matter 04

iTrader: (9)

Check the cylinder heads for the castech logo.
Pull the valve cover the symbol looks like a battery casted by the rocker arm stands .
Those were porous 706 castings that leaked slowly

Alex71

I have already determined it does not have castech heads when I pulled this earlier. and they are not 706's

BigDaddy0381

iTrader: (7)

862's ?

Alex71

Yes they are 862's

BigDaddy0381

iTrader: (7)

I had the same problem once a-pon a time. I would lose water and did all the test to find where it went. around town on short trips I wouldn't lose enough to notice right off it was slow. on longer rd trip I would have to add water every 250 miles or so. There was a hair-line crack that would let very little water slowly seep in the head and it would burn off with out being able to notice but only when engine was hot for long periods of time. I looked for the problem for about 6 months strong swapped most everything. I finally changed heads and it fixed my problem.

creedmore112

Having the same issue on a 03 Suburban Z71 with the 706 castech heads. What are my options on getting a better head that wont leak?

cammed00

iTrader: (2)

Bringing up the dead! I have an 04 z71 Tahoe losing coolant too with no visible leaks and it does have the 706 heads.