2006 GMC Sierra 5.3L

I was leaving Darlington this morning and my windshield was all fogged up, so I turned on the defroster, but it never warmed up, just kept blowing cold air. Once I got headed down the road, I noticed the temp gauge was about halfway between the 210 and 260 marks and I never see it over 210. I was kinda babying it along til I found a decent spot to pull into, but then it started coming down and settled back in at 210. I pulled into a gas station and checked the coolant level and it was definitely low, but there was some in the surge tank, so I didn't worry about it. I drove 2 hours home without any further issue.

At first I was thinking the thermostat had hung up, but that wouldn't cause the heater issue, would it? Most cooling systems have flow through the heater core even when the thermostat is closed, right? I topped it off with Dexcool this afternoon and took it around the block and it is running at 210 on the gauge like usual, so I figure it just had sucked in some air due to the low coolant level and then burped the bubble out or something.

So now the question is where did the coolant go. I don't recall ever having to add coolant to this truck. I can't find a leak. Head gasket? It has about 185k on the odometer.

9/5/2016 3:44:47 PM

need to pressure test system

[Edited on September 5, 2016 at 7:17 PM. Reason : not much help i know ]

9/5/2016 7:16:58 PM

yeah, i guess so

9/5/2016 9:26:44 PM

A or B

A. Head gasket

B. Water pump

I'm going to guess B.

9/5/2016 11:46:55 PM

I can't find a leak from the water pump weep hole

9/6/2016 7:26:45 AM

So it was fine until you turned on the defroster? Maybe the heater core is to blame...

9/6/2016 9:20:14 AM

I was thinking that water was always flowing through the heater core on this truck. I thought it just uses the blend doors to regulate temp.

9/6/2016 10:03:58 AM

lettuce know if you figure it out. i have the same engine in my truck

9/7/2016 9:43:52 AM

Getting it pressure tested tomorrow.

[Edited on September 7, 2016 at 12:41 PM. Reason : Kinda thinking head gasket or intake gasket at this point]

9/7/2016 12:38:40 PM

i thought those GM's had a heater control valve, it's the part with the vacuum hose going to it

9/7/2016 3:55:04 PM

I think the old ones did, but everything I find online says they aren't there on this generation.

[Edited on September 7, 2016 at 4:12 PM. Reason : Can't find one in the tree on rock auto either]

9/7/2016 4:10:02 PM

got it pressure tested at a really good indy shop today and it held pressure fine. they couldn't find anything. gonna keep an eye on the reservoir level and ride.

9/8/2016 6:10:44 PM

grab yourself a new radiator cap for a few bucks.

I've replaced a head gasket for that shit

9/8/2016 8:27:34 PM

it doesn't really have a radiator cap, just a cap on the overflow tank

9/8/2016 8:42:44 PM

it looks like the level in the bottle is still going down very slowly.

also, i think i've got a damn lifter making some noise now. it's when i first start it up and usually goes away within a minute.

9/17/2016 1:42:31 PM

http://www.agcoauto.com/content/news/p2_articleid/148

now i'm really worried

9/17/2016 7:03:34 PM

not sure how you'd do it without a radiator cap but if it's possible, go borrow a coolant system leak test kit from autozone/advance (~$200 deposit)

9/17/2016 8:07:53 PM

already had it pressure tested. they didn't find anything. this seems pretty common on these trucks and it's usually a cracked head. GM even put out a service bulletin on it.

9/17/2016 8:10:36 PM

Same thing happened to mine and was a head gasket. I drove it for about 50k miles with the crack, and would just top off the coolant every month. It did suck a couple times when I was sitting in traffic and it would start getting hot because the coolant level was low, but I always managed to get off the road. If you try to ride it out for a while, just make sure you watch the temp gauge whenever you are in sitting.

9/17/2016 9:08:33 PM

Same thing happened to mine and was a head gasket. I drove it for about 50k miles with the crack, and would just top off the coolant every month. It did suck a couple times when I was sitting in traffic and it would start getting hot because the coolant level was low, but I always managed to get off the road. If you try to ride it out for a while, just make sure you watch the temp gauge whenever you are in sitting.

i will say it was kind of a pain to figure out what the problem was. I had a gut feeling it was the head gasket, but the shops want to try every possible test before testing that because it can be hard to determine for sure if it's the head gasket if it's a tiny crack, or a little warp in the gasket.

9/17/2016 9:09:58 PM

what year model was yours?

[Edited on September 17, 2016 at 9:12 PM. Reason : 5.3 or 4.8?]

i'm gonna pull the valve cover tomorrow and check for the milky sludge that would indicate glycol in the oil and also for the casting mark that indicates the Castech heads.

[Edited on September 17, 2016 at 9:14 PM. Reason : if it has Castech heads, idk if i'm gonna replace them or just trade it in]

9/17/2016 9:12:31 PM

https://goo.gl/photos/sDADg5p1b4kcG6jv6

fuuuuuuuuuuuuuuuuuuuuu

so, to check the casting mark, you have to remove all the rockers on that side, so I didn't do that. i didn't see any obvious cracks in the oil drains like the GM TSB mentions, but that doesn't mean they're not there. now it's either pull the heads, get them PT'd, possibly replace the heads, pull the oil pan and clean out the dexcool snot, probably replace the lifters while i'm in there, and pray I didn't do any bottom end damage.

or trade the motherfucker in

dammit

9/18/2016 12:45:00 PM

i smell another H/C/I LS motor

9/18/2016 3:36:50 PM

No need to replace the whole motor, I don't think

9/18/2016 4:28:49 PM

change the oil and sell the bitch

9/18/2016 7:47:07 PM

nah, it's paid for and a comparable replacement with 50-80k miles already on it would be $25-30k

truck prices are insane with the taxes for low mpg that get passed on to the consumer nowadays

[Edited on September 18, 2016 at 8:32 PM. Reason : this thing only cost me $15k with 90k miles in 2011 or 2012]

my grandfather passed away last month, so i'm borrowing his truck while i get this one rolling again. 2005 silverado reg cab long bed with work truck trim. only 22k miles on the mighty 4.3L, but i'm gonna have to put some tires on it because they've sat so long they're dry rotting

[Edited on September 18, 2016 at 8:37 PM. Reason : afds]

9/18/2016 8:31:07 PM

she took a ride on a rollback today

9/19/2016 8:20:11 PM

did you at least cuss it, as dude was loading it up, with beer in hand?

9/20/2016 6:45:55 AM

Lol nah. I love the truck. Not her fault that GM gave her shitty heads.

9/20/2016 8:28:49 AM

The place I took it had this sitting in their shop, so I feel like it's in decent hands

9/20/2016 8:32:48 AM

unnecessary use of quotation marks.

Quote :

"WOULD NOT TRUST"

9/20/2016 10:57:04 AM

so i showed the guys at the shop the pic of the goo in the valve cover. they pressure checked it (again), did a hydrocarbon check on the coolant, took an oil sample from the pan, etc. i called him to check on it and he pretty much said there's nothing wrong with it, ride it. i said, "so i'm just supposed to drive it like normal and keep topping off the coolant every week or two?" and he didn't really know what to say. it's obviously losing coolant somewhere and me and two shops have searched for it externally and no one can find shit.

i asked "what about the goo under the valve cover? that's not normal." he gave me some crap about a little condensation under the valve cover and a possible leaking valve cover gasket. i told him i don't think that's a little water. it definitely appears to be the dexcool slime.

taking it somewhere else tomorrow and getting them to put dye in the coolant, run it, and check under the valve cover. i'm betting on cracked head.

9/21/2016 4:52:36 PM

Remove lines to the heater core and check for flow. My guess is clogged heater core. If so, flush it and it'll be fine.

Something else also comes to mind you need to check. Have you noticed a collapsed upper radiator hose after the engine cools? If so, run the cap to the overflow tank through a cycle in the dishwasher.



[Edited on September 21, 2016 at 10:12 PM. Reason : -]

9/21/2016 10:07:08 PM

heater works fine as long as I don't let it get low on coolant. did you look at anything other than the first post? check out the pic of what i found under the valve cover.

9/21/2016 10:10:24 PM

this pretty much describes everything i've seen so far: http://www.agcoauto.com/content/news/p2_articleid/148

9/21/2016 10:12:28 PM

okay

http://www.car-part.com

9/21/2016 10:17:47 PM

is that an "ok, you're right, it's not a clogged heater core" or an "ok, suit yourself, but i still think it's the heater core"?

because i'd much rather unclog the heater core if you think that's what could be causing my problem

[Edited on September 21, 2016 at 10:22 PM. Reason : adsf]

9/21/2016 10:21:55 PM

Try some of dat 190% radiator stop-leak?

9/22/2016 6:14:37 PM

never

9/22/2016 6:20:39 PM

9/23/2016 7:51:44 AM

long story short: the shop i took it to sucked hard. claimed it didn't have a coolant leak. they ran the truck a lot and never changed the oil because it looked like normal oil on the dipstick. i finally brought it home and changed the oil and sent an oil sample off for analysis. positive for glycol and 212 ppm lead. bearings are fucked, i guess. new engine or trade it

10/4/2016 8:44:51 PM

should have changed the oil and sold the bitch before you knew the problem

10/5/2016 8:51:19 AM

I can fix this for less than a down payment

10/5/2016 9:09:00 AM

10/5/2016 9:31:38 AM

Might have a lead on a freshly rebuilt long block at a good price. Hoping it works out.

10/5/2016 10:17:12 AM

hey man you're supposed to use unleaded gasoline.

10/5/2016 11:35:40 AM

My main bearings are missing some babbitt.

[Edited on October 5, 2016 at 1:13 PM. Reason : Presumably ]

10/5/2016 1:12:59 PM

Reman engine should be delivered Friday

10/5/2016 4:06:28 PM

You can get a 5.3 at a junk yard for DIRT cheap. Good luck

10/5/2016 5:07:25 PM

I would go the junkyard route if I planned to dump the thing soon. I plan to get another 184k out of it, though. I'm not comfortable sinking that much money into a junkyard engine with no warranty and no maintenance history and that may develop the same problem mine has now at any time.

Truck prices are insane now. I can't afford a new or used truck that is as nice as what I've already got.

[Edited on October 5, 2016 at 5:29 PM. Reason : 3 yr 100k mile warranty on the reman unit]

10/5/2016 5:29:06 PM