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Coolant Loss !

jocko50

By jocko50
in Ask A GM Technician

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jocko50 Enthusiast

jocko50

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I have a 99 Silverado with 5.3L and it has 102,000 miles. Problem that i am having is that i am losing coolant. Light comes on in truck and sure enough its down past the minimum in the resivor. Fill it up and i am ok for about 2 weeks and same thing over and over. Truck runs fine, Dry plugs, no external leaks(water pump etc) Pressure tested OK. Took valve cover off and found this butterscotch looking stuff stuck to the inside valve cover(coolant???). Any info greatly appreciated. Are these 5.3L known for this type of problem? I was told Intake gaskets will not solve this problem. Are head Gaskets next?? Thank you. :lol:

jocko50 Enthusiast

jocko50

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Any butterscotch on the dip stick?

 

 

No, Doesn't seem to be any in the oil. Only thing in the oil is some light sludge (black) which seems to be from engine cleaner Additive which was put in to motor a while ago. The valve train looks a little dirty(from previous owner not changing oil often)? Thanks for reply!!

Zembonez Senior Enthusiast

Zembonez

Posted
Posted
Any butterscotch on the dip stick?

 

 

No, Doesn't seem to be any in the oil. Only thing in the oil is some light sludge (black) which seems to be from engine cleaner Additive which was put in to motor a while ago. The valve train looks a little dirty(from previous owner not changing oil often)? Thanks for reply!!

 

Do a pressure leakdown test on the cooling system to see if there is a leak (either internal or external). My guess is that you have a headgasket leak somewhere...

jocko50 Enthusiast

jocko50

Posted
  • Author
Posted
Any butterscotch on the dip stick?

 

 

No, Doesn't seem to be any in the oil. Only thing in the oil is some light sludge (black) which seems to be from engine cleaner Additive which was put in to motor a while ago. The valve train looks a little dirty(from previous owner not changing oil often)? Thanks for reply!!

 

Do a pressure leakdown test on the cooling system to see if there is a leak (either internal or external). My guess is that you have a headgasket leak somewhere...

 

 

I have already done a pressure test and it held up fine. Did one test cold and one hot and no leaks. Thank you for your time. I don't want to do any repairs that i don't have to but it is looking more and more like a head gasket. Anything else you can suggest?

merlin5577 Senior Enthusiast

merlin5577

Posted
Posted

Jocko,

 

When you are trying to diagnose a problem it is always a good idea to start with the small things first. I had a problem like this a while back with an 86' monte carlo I had. Every month or so it would leak an entire reservoir worth of coolant. No leaks anywhere, no coolant in the oil. Stumped me for months. Turns out I had a hairline crack on the underside of the radiator hose that when the thermostat opened pressurized the upper radiator hose and allowed coolant to run down the radiator and pool on the lower radiator support. When the engine warmed up more, the rubber swelled and it stopped leaking, then when it got hot enough it boiled off all the pooled coolant at the bottom. Only reason I figured this out was that one side of my radiator turned green from the coolant. My point is, when faced with a big problem, take it one step at a time. I hope this helps.

gm4yrs Enthusiast

gm4yrs

Posted
Posted
I have a 99 Silverado with 5.3L and it has 102,000 miles. Problem that i am having is that i am losing coolant. Light comes on in truck and sure enough its down past the minimum in the resivor. Fill it up and i am ok for about 2 weeks and same thing over and over. Truck runs fine, Dry plugs, no external leaks(water pump etc) Pressure tested OK. Took valve cover off and found this butterscotch looking stuff stuck to the inside valve cover(coolant???). Any info greatly appreciated. Are these 5.3L known for this type of problem? I was told Intake gaskets will not solve this problem. Are head Gaskets next?? Thank you. :D

 

On my 1999 silverado, I was loosing coolant too. Resivior would be low and I would refill it, and about 2 weeks later, coolant low again. I seen no visible leaks, cold or hot, but noticed a white (alkali) water line, on the bottom of the oil pan. I traced it to the water pump "seep hole" and replaced the water pump. This occured around 95,000 miles. It probably leaks while your driving (under pressure).

jocko50 Enthusiast

jocko50

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Thanks for your help guys. I guess i will start with the water pump gasket first(and replace thermostat while im there) and see what happens. process of elimination as they say!!!!

merlin5577 Senior Enthusiast

merlin5577

Posted
Posted
Thanks for your help guys. I guess i will start with the water pump gasket first(and replace thermostat while im there) and see what happens. process of elimination as they say!!!!

 

 

Thats the way to do it. :thumbs:

anealysr Enthusiast

anealysr

Posted
Posted

I had a 98 Z71 that was doing the same thing. I found it the hard was as it was the heater hose fitting and it exploded later. They are made of cheap pot metal and will break down over time. I replace it with a steel one from NAPA for about $7.00.

  • 1 month later...
jocko50 Enthusiast

jocko50

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Well after checking a few easy things first like hoses and clamps and inspecting water pump and surrounding area i decided to replace the intake manifold to try and solve the loss of coolant issue i was having. I came to this conclusion by reading a post somewere here about Dextrol coolant and air coming in contact with it which will produce a butterscotch residue. I know the intake is a "dry system" but it seems to have solved the problem for now. Over 3000 miles and NO COOLANT LOSS !!!!!!. Maybe air was getting buy the gasket and some how mixing in with coolant through those tubes??? Now if i could only get rid of that Horibble Piston slap everymorning now that it getting a litlle colder outside. Truck sounds like a disel for a minute. THANK YOUS.

jocko50 Enthusiast

jocko50

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Well by "the book" It says its a 5 hour job but i had my mechanic friend do it for me after i told him to change that gasket because he did not want to make the call because he was stumped at what it could actually be. We both had our opinions but it was my call. Hope this is a long term soloution.

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