'97 Suburban Coolant Issues

Just picked up my 1997 Suburban 4x4 1500. It currently has 156,000 miles. I bought it on a spur of the moment decision because the price was so good that I couldn't refuse it. Besides most of the common wear and tear issues it drives and run really nice, but I believe I maybe having some sort of issue with the water pump/cooling system. When I first looked at the burb I noticed it had NO coolant in the reservoir tank. I didn't see any traces of coolant on the ground, but knew that the burb had pretty much sat in the same spot for the last 6 months. After filling up the reservoir tank and driving it for a while I noticed that all the coolant I had poured into the tank was gone! I refilled the tank to the full mark again then watched it slowly drain some more. On top of all of this, I checked the codes from the computer at came up with P0125. P0125 says that the Coolant temp is always low according to the engine coolant temp sensor. It seems ironic to me that a car with very low coolant is running too cool.

My plan of attack was to try and pick up both a Thermostat and ECT sensor since they are both under 20 bucks and see what happens. Any thoughts/suggestions/advice are very much appreciated! I look forward to getting to know the Suburban crew!

Be sure to check & make sure that the intake gasket is not seeping on the corners where it meets the block & heads. These were bad about leaking when they get some miles on them and is usually a slow coolant loss & sometimes rolls down the back accross the transmission bellhousing. Sounds like your on the right track with the thermostat & sensor. Be sure to install a 195 degree thermostat because that will keep your engine temp running where the ECU wants it. If the water pump has not been replaced I would do it when you do the thermostat because the do fail on the 5.7 more than the 5.3. Good Luck

I have never replaced a thermostat or coolant temp sensor before, but the guy at Auto Zone seemed to think I would have no problem doing so. I am very familar around cars, I just don't often tackle my own repairs. I usually just do preventative maitenance. I will probably invest in a Haynes or Chiltons guide before I start any work. Can anyone offer any suggestions or tips for replacing these?

I noticed last night that there was some greasy build up on the drivers side valve cover. It was pretty dark out so I couldn't tell where it was coming from, but I think I might be looking a leaking intake gasket. If it is indeed leaking, how emergent is this kind of repair?

If you are losing coolant, replacing the tstat and ECT sensor is not going to help you. You need to find the source of the leak. The intake manifold gaskets are known to be an issue and have been redesigned.

A pressure test would be the right place to start.

//2000CAYukon

I believe I may be dealin with more then one issue right now because my check engine light has been on and the a scan of the computer says the burb isn't reaching operating temperature. This makes me think that thermostat may be bad. At the same time, I maybe looking at a bad intake manifold gasket as well.