J
Jack Klarich
Guest
The Radiator cap is on the over flow tank, These motors are famous for cracking heads and blowing head gaskets
07 Silverado Coolant loss
- Thread starter Mavagrand
- Start date
before you go replacing head gaskets - pressure test the cooling system . have not found a head gasket yet on any of newer gm engines for a long time . check all of the spring type hose clamps - the one on the bottom of rad breaks most often and slowly leaks coolant. also take close look at water pump for track marks down front of engine . the other thing is how much coolant are you going thru.
I'm not sure if they are still the same as my 01, It did the same thing. My water pump was leaking when it was running and I couldnt find the leak either. It finally started to leak more at the weephole just above the crankshaft pulley. That's where most of them start. It had 209000 miles on it then. Another note-I didnt know there was another belt on this engine untill I took the water pump off, the skid plate hides it.
R_W_B
Senior Member
Wow don't know how I missed this thread. Anyhow my Silverado is an older 350 V8 with cast iron heads. But here are some key things to check.
First off go ahead and replace the thermostat, it may be sticking enough to cause the computer to throw a code but yet it still isn't enough to overheat.
Do you have a heat gauge or are you just going by the fact that it doesn't steam up ?
Get under you truck when it's cool, search for any traces of leaks on the sides of the bock or at the hoses, water pump or radiator. There is usually a small hex bolt drain plug on one side of the block (at least on mine) and on the other side the Knock sensor is also a drain plug (if yours doesn't have the newer ION knock sensor). If you don't see any evidence of a leak, then carefully get under your truck while the engine is idling and look.
If you have a very bad leak at the head gasket you are gonna have a white color goopy looking oil on your dipstick and/or your coolant will also be discolored.
I recommend those "Fail Safe" thermostats since if they stick (fail) they have a release mechanism that will force it all the way open. Thereby saving you from overheating but also throwing a code (by running too cool) and alerting you of a problem. You may have one already in your truck causing the code.
First off go ahead and replace the thermostat, it may be sticking enough to cause the computer to throw a code but yet it still isn't enough to overheat.
Do you have a heat gauge or are you just going by the fact that it doesn't steam up ?
Get under you truck when it's cool, search for any traces of leaks on the sides of the bock or at the hoses, water pump or radiator. There is usually a small hex bolt drain plug on one side of the block (at least on mine) and on the other side the Knock sensor is also a drain plug (if yours doesn't have the newer ION knock sensor). If you don't see any evidence of a leak, then carefully get under your truck while the engine is idling and look.
If you have a very bad leak at the head gasket you are gonna have a white color goopy looking oil on your dipstick and/or your coolant will also be discolored.
I recommend those "Fail Safe" thermostats since if they stick (fail) they have a release mechanism that will force it all the way open. Thereby saving you from overheating but also throwing a code (by running too cool) and alerting you of a problem. You may have one already in your truck causing the code.
Have a mechanic do a pressure check, he will need the right adapters. those engines have plastic intakes I think. GM has problems with those intake gaskets leaking, I have done several on the smaller V6's and the 5.3 v8's. I don't ever recommend stop leak, have rebuilt too many engines where, when cleaning the block, an entire water jacket is packed with that junk and cylinder ran hot.
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R_W_B
Senior Member
OMG plastic intakes, yet another reason to keep my old 1988 cast iron 350 and keep fixing it. LOL
That's some interesting information on the leak products. Never really knew what to think about them, but last year I started having loss of coolant (slowly over a period of 2 weeks the radiator would be low). So I tried pouring in some kind of leak fix stuff I bought, can't remember what it was.
Anyhow it kept losing coolant the same way. Well recently I pulled the heads off and sent them to a machine shop for a valve job. While I had it all apart I pulled both drain plugs on either side of the block. They did not drain immediately so I polked around a good bit with a bent 12d nail and then it started flowing.
Now I know from past experience etc, that these plugs are said by mechanics to stop up that way over time "just from rust scale alone". And I don't doubt that especially since my truck has 158,xxx miles on it.
But the stuff that first came gushing out looked more like a thick black syrup than rust. Then later it started to look more like rust scale. So that could have very well been from the leak fixer.
So I filled a narrow spout plant water container and poured several fillings thru the block cylinder jacket holes to flush it all out clear before I replaced the drain plugs. Anyhow just thought I would share that. Decide on your own.
Oh and BTW I bought a new radiator to fix the slow leak.
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