I have a 2001 LT Surburban that has always run great. About 6 months ago I started having to add about 2 quarts of coolant every 2-3 weeks. There are no visible signs of coolant anywhere I look
-on the ground where I park after driving
-checked all hoses
-anywhere on the engine, and I don't smell coolant under the hood
anywhere below the engine on the plates or elsewhere on the frame.
I put a new water pump on about 2 years ago and it there was not leakage after that for 18 months. I don't even see leakage signs out of the weep hole on the new pump like I did before I replaced the old one.
I drove the car to Florida and back (2K miles) and the level was fine, it is just the city driving that does this.
What should I look for or what next steps should I take?
I have a 1999 Suburban that kept losong coolant. I found that one of the gaskets between the waterpump and the block was leaking. However you say there are NO signs of leakage. Get yourself a radiator pressure tester and pressurize the cooling system for about fifteen minutes to see if it loses pressure. If it does, and there are still no signs of leakage a good possibility is that you may have a small head gasket leak into a cylinder. One way to check that is to do a compression test on each cylinder. Good luck, I hope this info helps you.
I have the exact same vehicle and had the exact same problem. Mine turned out to be a slow leak on the water pump gasket, doesn't sound like your problem though. I would look to make sure you dont have either a front or rear heater core leak or line leak. It sounds like you did a thorough underhood inspection, so if all these items prove ok, then look to the engine itself or tranny cooler, smell the exhaust for coolant and let the engine set overnight and change the oil to check for streaks of coolant in the oil or white goopy creap under the oil cap, both would indicate an internal leak. next, run it for awhile and check for coolant in the tranny fluid or vice versa, which is very serious because coolant eats clutches. any more questions let me know i know these vehicles inside and out.
check the gm tsbs they were aware of this problem and did it seems a hidden tsb they are fully aware of the problem look at your stamp on the heads and see what it says write it down look up the tsb i cant remember what the stamp on the head said but thats the probvlem its a small crack just enough to loose fluid and evaporate in the engine thats why your not seeing anything again research the past tebs youll find it no garages want to touch it i know i have the same problem on a 2002 suburban 5.3l flex and evry garage i talked to says they are unaware of it bunch of hidden bull
I have that same problem on my 1999 suburban 5.7. I found it to be the little rubber cap on a misc. port right under my filler neck on the radiator. I don't know what this single capped port was/is used for but the cap can't deal with the pressures and heat in the radiator. I could never find any leaks until I pushed this rubber cap while my engine was warm and running at idle then I saw coolant drip out. I now have to change this cap about every 6 months to a year. Does anyone know what this port is used for? thanks
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