Coolant tank almost empty

wayne36 · October 2, 2014

I have a 2004 1500 silverado 160k miles and I have never had problem with it before but today I was out in town extreme coolant temp came on and the temp was pegged out I get out and check and the tank was almost empty it took almost a whole gallon to refill. I have never seen any leaks or over flows. Do I have a cracked head or a bad head gasket?

SouthernSilveradoGuy85 · October 2, 2014

Yes it is a 5.3 and I refilled it at last oil change, I just checked it and it 1" low sense top it off.

That's just the air finding it's way back to the top. Just have to look around the engine bay and look for where it's coming from. Even if you have to start from the bottom by crawling underneath. You just have to trace it to where it's coming from. It could just be a water pump gasket or something small.

wayne36 · October 7, 2014

The adaptor that comes with it just screws on the coolant tank but there was nothing stopping the air from escaping out the overflow port and no it didn't have any pictures and I ask the guy at auto zone and he didn't know of anything.

Kent2500 · October 4, 2014

The engine has a fan and my rad is a sealed one mean it doesn't have a rad cap. topped it off again ran it up to temp for 10 mins with a new coolant tank cap to if anything happens over night as in leaks.

You should pressure test the system. My 2000 Tahoe didn't have any "visible" leaks on the ground, but pumped it up to 15psi and coolant was spraying out of the water pump.

wayne36 · October 2, 2014

I have been looking and not seeing sign of it dropping on the ground I'm just going to take it to the shop tomorrow and have test it. Thanks for the help.

Doug_Scott · October 4, 2014

Take a look at the Castech cyl head TSB from GM. I found a post at http://www.gm-trucks.com/forums/topic/119868-castech-heads/?hl=06-06-01-019b&do=findComment&comment=1068667

Your truck appears to be right in the middle of the range. I would be looking closely at the oil coming out of the engine for any coolant. Best time to check is to pull drain plug from oil pan first thing in morning before running the engine at all that day. If you are quick and pay attention, you can loosen the plug until it is just about to come out and look at the fluid leaking out. If it is not oil, then you likely have bad heads. If you have proper coolant in the rad, it will be very easy to see when it starts to come out around the threads.

Reason for cold engine is that oil is lighter than water and coolant, so after sitting for 12 hours or so, any coolant existing the oil due to being pumped together will have separated back out again, and will be in lowest part of the oil pan. The oil pump pick up sits at the bottom of the pan, so it pulls whatever is sitting in the lowest point. If you run the engine before checking the drain plug, you will not get a proper reading.

You could also take a look under a valve cover for any sludge from coolant in the oil. It will appear as a brown slimy gooey mess.

wayne36 · October 6, 2014

Went to auto zone to get a pressure test kit and I had a problem with air escaping out the overflow port.

Doug_Scott · October 6, 2014

Went to auto zone to get a pressure test kit and I had a problem with air escaping out the overflow port.

What pressure was it at when it started to leak? Does the pressure tester replace the rad cap?

Doug_Scott · October 7, 2014

The adaptor that comes with it just screws on the coolant tank but there was nothing stopping the air from escaping out the overflow port and no it didn't have any pictures and I ask the guy at auto zone and he didn't know of anything.

Take the hose off the other end and plug it with a similar sized bolt and hose clamp? That will stop air from coming out the overflow port.

Doug_Scott · October 7, 2014

It sounds like you need an adaptor for the pressure tester. The rad cap must not be the old style push down/quarter turn cap that I know about. Did the tester come with any instructions or pictures? Have you checked online at the tester's maker website for instructions?

Doug_Scott · October 3, 2014

Depending on where you park it, and where you live, try putting a piece of cardboard under the engine when you park it at end of day. Next morning look for any coloured spots(assuming you use coolant and not just water).

The engine will not overheat just because the reservoir is empty. Reservoir is not part of the active cooling system, it is part of the reserve. If it is overheating, then there must be something wrong on the other side of the rad cap. If engine is cold, take rad cap off and check coolant level. Add till radiator is full. After you have driven if for the day, let the engine cool off completely and take rad cap off and check level again. Make sure it is full. Do not be surprised it if needs a second fill.

wayne36 · October 3, 2014

I have checked over under and around the engine no signs of a leak I went and got a new cap. I have had this truck sense 2009 and it has never over heated until yesterday and so far it hasn't done it again. it's just strange that sitting in a parking lot for 5 mins the temp jumped to 260 and the outside temp was about 80.

Doug_Scott · October 3, 2014

Is the cooling fan coming on? The electric fan on the rad should be running at temps over 210 or so. Or does your engine have the actual fan on the water pump? If it does, and if it is a clutch fan, make sure the fan still has some friction in the clutch.

Make sure the rad is actually full of coolant now.

wayne36 · October 7, 2014

The pressure tester cap replaces the over flow cap and it won't pressurize unless you put your finger over the overflow drain and I was able to get it up pressure. Do they make something to block that drain tube?

8.1HD/ALLISON · October 2, 2014

Hard telling. Fill system and pressure test to find leak.

wayne36 · October 19, 2014

Just a little update I have done everything I know to do and the truck has ran fine with no over heated issues or coolant loss. So it was either the rad cap or if you believe in other things the day after the truck over heated we were suppose to travel to my in laws for a quick weekend visit which we didn't go because of the over heating issue and just so happen that day my short term disability payment was screwed up. Who knows we travel the following weekend with no problems and a good visit.