Cooling system K2500 What's normal?

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Posted by R. Staaterman ( on 10:26:15 02/27/08

I've had this 99 K2500 7.4L Suburban for about 4 years now
and I've used it mostly for towing my race trailer (7K lbs). It's been fine and regular service on the trans and diff with Mobil 1 synthetics have been performed.

About a year ago I noticed that I was losing coolant.
Yes the manifold fitting was replace just before I bought it. Well in looking things over it looked like the water pump was leaking some and so I installed a new pump, hoses, belt and tensioner. This at a little over 100K miles. But since that time I've noticed that the temperature gauge seems to fluctuate a lot and so I suspected an air bubble. I did make quite the effort to bleed the air out via that quick connect for the heater hose on the manifold. Then I did a pressure test by inserting one of those Prestone service tees in the heater line. I saw no problems.

So today (it's 41F) I warm it up to about 150F take it out and drive it. It stays at 160-165 until I stop. Then it goes up to 190. If I turn the key off for a minute or so and back on it drops down to 165-170F.

It will heat up like this when stopped at a light too.
Then cool down when you get going again.

It appears that the fans are on.

So what's normal or abnormal about this?

What is the proper operating temp of the coolant?

I did tow once last summer for a couple of 100 mile trips with it performing like this and it never boiled over.

Thanks for any tips.


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