99 Tahoe Coolant issue

Hello all, first post here but great site!!!!

Sorry long post

Ok - I have a 99 Tahoe 4x4 350 90k+miles.
I have had for bout 2 yrs, no problems - she isn't driven daily, have daily drivers that wife and I abuse. But the 'hoe does get a work out when used - has hauled my Runner atleast a dozen times and a couple long trips.

A couple weeks ago noticed, she ran a bit warm - past the usual mark - never overheated - no steam popped. I changed Thermo & gasket and topped off fluid (Orange - I know not best, but its in there) she was alil low on fluid, by close to a gal, and I didnt spill that much at the housing.
Now I keep an eye on fluids, the overflow will go empty, rad is still full, but this has been short trips.

I didn't notice any leaks anywhere - I will be looking at closly later.
Any main areas to look? Obviously I'll give the rad a good look over but if its the water pump, any good way to pin point that as issue?? Possibly an idea if another culprit??? Winter is gettin close and I wanna take care of in the first shot....

TIA
John

Welcome to AF. Get the system pressure tested, if no visible external leak suspect intake gaskets, also look at the oil filler cap see if there are any signs of milkiness under it.

Let's do the math...

You have a '99 Taco (that's seven years old). It has under 100,000 miles.

You've owned it for two years (since it was five years old).

PLUS - The required change interval for DexCool is 5 years/100,000 miles.

Unless there is proof that the previous owner had the system flushed and refilled just before selling/trading it (highly doubtful) you should have flushed the system two years ago.

PLUS - It has been operated at a low level (almost a gallon) for some undetermined amount of time. Operation with any air in the system accelerates the formation of solids, especially true in OA coolant systems (DexCool).

EQUALS - If you haven't drained, flushed, and changed the coolant by now, it's well beyond the due date.

The Wedge-Block Man is all over it. This is an excellent time to pressure test the system, since the old coolant needs to be drained anyway. Any repairs determined necessary as a result of the tests are an opportunity, not a problem. The Vortec V-8s don't seem to suffer head gasket problems like some of the 60º V-6s, and don't have as many intake leaks. It's possible that leakage could be anywhere from a water pump seal to a heater core.

Does the system create and hold pressure once the engine has been fully warmed? If not, there is likely a problem somewhere.

Does the engine oil have a milky appearance or higher than normal level? Is there excessive moisture (steam) in the exhaust stream even after the vehicle has been warmed and driven? Those are also indications of internal coolant leakage.

That pressure test can help reveal if and where that leakage may be occurring.

Ok - It appeared to the water pump so far so good....

Had a few issues hit me all at once - Service Engine lite came on - Pass O2 sensor (before cat - so said autozones reader)
So picked up O2 sensor, Waterpump & a gal of AF, and a pair of rear turn lamps - rt turn quit working..... Oh and while apart did serp belt too....

knocked out in 4-5 hrs with a few runs back to store - needed fan wrench. given wrong size belt...

So far all is back to norm (good thing before winter)....

A shot of the ole girl : ) http://www.trcdtoys.com/Wheels/slides/Tahoe%20007.jpg