mysterious coolant leak now in oil

[dns04av]

I had this mysterious coolant leak for several months now and has been getting worse. Some weeks I'd add  1-1.5 gallons of coolant and other times I could go 3 weeks before adding anything. Didn't seem to matter on the mileage either.

This is on an 04 Av with the 5.3L. has about 60k miles.

I put a dye in the coolant and checked for external leaks....none to be found.

Now I found that the coolant is going into the oil (coolant level down/oil level up). This has only started a few days ago thought. My thoughts were a head gasket so I just did a compression test. Here are the results:

cylinder 1 - 139,   3 - 162,  5 - 160,  7 - 160,   2 - 168,  4 - 161,  6 - 161 and 8 - 165.

I thought that if it was a head gasket, I would have 2 low cylinders but looks like only one is low (139) and even that isn't too far from the others.  What else should I look for. Should I remove the valve cover and look for cracks like in the TSB about Castech (sp) heads?

[MyBigToy]

Bars Leaks has an additive that supposedly fixes head gasket leaks. I'd suggest you get a can of it and give it a try, sooner rather than later. You may already have waited too long. At this point you've got nothing to lose by trying it.

[dns04av]

I don't plan on driving it until I fix the problem....replace head gasket(s) or head(s) as required. Like you say, hopefully I didn't wait too long. Tomorrow, I'll pul the valve covers off and see what that looks like.

[ItsStopher]

Have you seen this thread?

[CodeBlueEMT]

 ItsStopher,

 That's the first thing I thought of when I saw this current thread.

 Shayne

[dns04av]

yes I did see that thread....sounds a lot like my problem. will investigate some more tomorrow.

[dns04av]

Took the valve covers off today.....man is that ugly looking. The covers themselves look like someone sprayed whip cream all over the inside. The rockers and springs are all covered in black sludge.  It looks like the casteck logo on the heads but kind of difficult to see their logo without taking the rockers and the pivot support (think that's what its called) off. I don't want to dismantle too far just yet, I still have to drive it from the carport to the garage (once I finish insulating inside. Other project on the go).

You can see coolant in the oil drain back holes in the heads, especially the ones on the driver's side head. I had previously added a dye to the coolant so it shows up bright green.

I took some pictures and will try to post later.

[dns04av]

Here are some pics

[dns04av]

I need some options now......what's everyone think

1. should I just change the heads and flush the oil and hope the rest of the engine didn't get TOO damaged?

2. get replacement engine - scrap yard - might have same problem as this one?

[themoneypit]

i would start with the heads, and then do a good engine flush and see how you make out.. worst case, if it blows up, and you buy a junkyard motor, you'll have new heads to put on it b4 the install

[MS03 2500]

I kind of agree just do the heads, any damage that was going to happen has happen already. And change the oil at least 3 times afterwards.

[dns04av]

So if I replace the heads, how or what should I do to clean the rest of the engine?

Should I just do multiple oil changes after installing the heads and hope that flushes everything out?

TIA,
Dean

[MS03 2500]

I not sure how much experince you have at this. So before I answer have you ever changed a cylinder head before.

[dns04av]

Would be first time on this LS type engine but have changed a few head gaskets, installed cams, heads, intakes on 1st gen engines.

[MS03 2500]

OK as long as you have done something like it before. First try the clean the Valve cover with brake cleaner to see if that stuff comes off, remove all rubber parts first though and we will see how hard is it going to be. Do it in a open area outside of the garage it's flammable

[dns04av]

I put everything back together, I need to finish some work in the garage before I can bring the truck in to do this head job. Not going to drive it just will need to move it to the garage.

I did wipe out the valve covers though. It just cleaned off with a rag. The black gunk on the rockers would wipe off too just a little sticky - kind of like thick oil.

It will be a couple of weeks before I can get back to it. Just trying to come up with a plan right now.

[MS03 2500]

That is good, one of the things you are going to have to do is remove the oil pan and clean it. Think about replacing the oil pump or some how clean it. The lifters and rods are going to have to be cleaned also.

But if I tried this I would remove the pan and oil pump leaving the old heads on, but remove the lifters and spray the heck out of everything in the valve valley and the heads and let it drain.

Added The cooling system will have to be flushed also.

Brake cleaner will remove almost anything (thanks BigC).


Understand this the damage may have been done already so no guarantee on this.

[ygmn]

Big messy job.
Just change haeds or have them tested or dye penetrent tested for cracks.
but.. if it ends up heads DIY.
you will remove intake so you get to clean a lot.
and when intake is off..remove oil plug put big pan and pour oil down intake to fludh out dirt.
Light weight oil works like tranny fluid or SAE 10 weight ot hydraulic fluid..
flush til clean.
then start flushing with engine oil. until only engine oil is in there..
then plug her back up and re-ASSY.

[MS03 2500]

I don't think so

It's probably in the bearing Cam and Crank.

[dns04av]

Thanks for the cleaning info. I'll give that a try and see how it turns out.

Now just have to decide on some heads. Thinking aftermarket, searching for stock specs to compare to . Don't really need more performance, just want better heads. (aftermarket seems cheaper than ones from dealer). Just trying to match (as close as possible) to orighinal, don't want to mess with tunning.

[MS03 2500]

Can't help you on the heads, but someone may chime in and help you.

[dns04av]

I decided to go with reman heads from a local engine shop. I'll picking them up on Friday and see how far I get on the weekend.
Thanks for all the help.
Dean

[Djurre-Avalanche]

I decided to go with reman heads from a local engine shop. I'll picking them up on Friday and see how far I get on the weekend.
Thanks for all the help.
Dean

Are you sure your engine knocking isn't related to this problem?

[dns04av]

The knocking was always there, even before the coolant disappearing. It was starting to "tick" though - valvetrain noise- which is probably because of this coolant/oil problem.....will soon find out I guess.

[Djurre-Avalanche]

The knocking was always there, even before the coolant disappearing. It was starting to "tick" though - valvetrain noise- which is probably because of this coolant/oil problem.....will soon find out I guess.

Oh okay i understand.
I'll hope for you the costs aren't too high 

Is a cracked Castech head very common on Avalanches?
Let's say out of 10 Avalanches, how many will get problems with cracked heads?