Low coolant light

Deadi · May 21, 2006

This is my first post here so be gentle. I have a 2002 GMC Sierra Z71 with a 5.3 liter motor. My low coolant light has been comming on for some time, and I checked coolant levelels and they were ok. Then about a month ago I noticed that the coolant was a little low so added some antifreeze. Fixed the problem until last week and again noticed that the coolant was low. I don't see any coolant in the garage floor. Anyway where is the first place that I should be looking for the problem. Any help would be appreciated.

Norseman · April 16, 2008

I'm having the same issue as stated above. My 2003 5.3 has been loosing antifreeze and I can't tell where it is going. I have checked trann fluid and oil. I have checked all visible clamps. Just yesterday I started my truck and got it up to temp. I checked and could not find any leaks. I also was unable to smell any odor of antifreeze inside the cab and under the hood. I'm still looking to try and figure out what the issue is.

Try putting a new WP gasket on. Read above.

J-rod · December 20, 2006

Check around the front and back of the intake. i know several people (including myself) with Vortec V8's that have intake gaskets. They usually leak out rather than into the combustion chamber. You should be able to smell the antifreeze when the engine is hot if this is the case.

<{POST_SNAPBACK}>

I've had the same issue described in the original post for quite some time now (close to 2 years). I'm not sure that its always been as bad as it is now, but at this point the light comes on about once a month. When I check the level, it takes about a 1/2 gallon of coolant to get it back up to the line.

There is most definitely no coolant in the oil and while I can see some on the bottom of the engine, there is never a puddle so it must only leak when its running and evaporate from the heat of the engine. And yes, you can smell it sometimes.

I have a feeling its a leaky water pump, but haven't confirmed that. Would you guys guess the same? And if that's it, has anyone changed theirs? Is that a DIY type project or should I leave it to a dealer? And finally, how much $$$ am I looking at if I do replace it? If the cost is very much, I'm inclined to just refill once a month for now.

mmmikkke · May 21, 2006

Your truck has Dexcool, GM's silicate free long life antifreeze. It's orange tinted. While it normally can last 100,000 miles or more, if it gets too much air exposure, and especially if it gets aireated, it can turn into a real mess of jell and gook.

So I'm just giving you some gentle advice: Until you find where your coolant is going, make sure you top it off often to minimize how much air gets in it. And make sure you use the orange tinted antifreeze. The green stuff will shorten its life.

Mgd406 · December 20, 2006

Buy a new radiator cap.

Markus

Goodwrench · May 22, 2006

This is my first post here so be gentle. I have a 2002 GMC Sierra Z71 with a 5.3 liter motor. My low coolant light has been comming on for some time, and I checked coolant levelels and they were ok. Then about a month ago I noticed that the coolant was a little low so added some antifreeze. Fixed the problem until last week and again noticed that the coolant was low. I don't see any coolant in the garage floor. Anyway where is the first place that I should be looking for the problem. Any help would be appreciated.

<{POST_SNAPBACK}>

Check your oil dipstick. If you have an intake manifold leak, the engine can ingest coolant. It may cause the oil to look milky.

Use the OBD II scanner to look at your fuel/air mix and injector dwell time. If the open time is high, it's trying to compensate for an air leak.

Norseman · December 21, 2006

If you do replace the pump, use a new one and not a reman unit and I would suggest replacing the thermostat at the same time. It is also a good time to look at your belts while you have them off and replace them if needed. I am in the Auto Parts business but am not trying to get you to spend money you do not need to spend. It just makes good sense to do the job 100% while you have it down.

Agreed. I would add just one thing to what was said above. DON'T use the POS gasket that comes with the new pump. USE the metal Fel-Pro gasket.

Note to those that own a 5.3l engine:

The 5.3 has a dry intake. NO coolant flows through it. So that means a intake leak will NOT put coolant in your oil.

Note to those that own the 5.7:

Please read above and stop telling people that own the 5.3 that a intake leak will put coolant in their oil. Thank you.

C & A s Dad · December 20, 2006

Jarod, if it is the WP I would not wait. It will not produce a slow leak forever and one day it will leak heavily and put you down on the road. I have not personally changed the pump on a 5.3L but others here have. I do not feel it is difficult job and you can handle it if you are mechanically inclined. If not, take it to a prof tech. Either way, make sure you flush the system very good and refill it with the proper coolant. I also use and highly recommend Kool It by Lubegard. It is a wonderful product and will eliminate all chemical electrolysis in your system.

If you do replace the pump, use a new one and not a reman unit and I would suggest replacing the thermostat at the same time. It is also a good time to look at your belts while you have them off and replace them if needed. I am in the Auto Parts business but am not trying to get you to spend money you do not need to spend. It just makes good sense to do the job 100% while you have it down.

ChevyTech007 · May 22, 2006

Check you oil filler cap, if it does not have a milky film inside I would not worry about an internal leak. Most probable cause is a water pump or water pump gaskets. I have seen them leak intermittently so it might not leak all the time.

Silverado2003 · April 17, 2008

I'm having the same issue as stated above. My 2003 5.3 has been loosing antifreeze and I can't tell where it is going. I have checked trann fluid and oil. I have checked all visible clamps. Just yesterday I started my truck and got it up to temp. I checked and could not find any leaks. I also was unable to smell any odor of antifreeze inside the cab and under the hood. I'm still looking to try and figure out what the issue is.

Try putting a new WP gasket on. Read above.

Will be doing. Hope it solves the problem.

sagent · May 22, 2006

My 02 Sierra did the same thing. Take a good look around the water pump pulley. Took about a year for me to confirm it was the water pump. I think the leaks start off so small the droplets of antifreeze evaporate as they hit the hot engine hence no visible leaks.

Silverado2003 · April 16, 2008

I'm having the same issue as stated above. My 2003 5.3 has been loosing antifreeze and I can't tell where it is going. I have checked trann fluid and oil. I have checked all visible clamps. Just yesterday I started my truck and got it up to temp. I checked and could not find any leaks. I also was unable to smell any odor of antifreeze inside the cab and under the hood. I'm still looking to try and figure out what the issue is.

joegreen42 · May 15, 2008

So.. Did it solve the problem??

chev9644 · May 26, 2006

Check around the front and back of the intake. i know several people (including myself) with Vortec V8's that have intake gaskets. They usually leak out rather than into the combustion chamber. You should be able to smell the antifreeze when the engine is hot if this is the case.