Well friends, I am very happy with this forum. Last spring I purchased a 98 LT for my son. It has 160K on it, and the previous owner was religious in changing the oil, flushing the cooling system, and generally repairing things such as faulty poppets with the new injectors. So, in short it has been well taken care of.

Down here in Kansas we don't get to many sub zero days, but we get a few and my boy drove home from a friends and told me he heard a gurgling sound under the hood. He wisely shut it off and I later learned the coolant was leaking from somewhere. I filled it up, ran it and no leaks were noticed. I had him drive it with no issues. Coolant seemed to stay full.

Then we had a cold snap, I was driving the car, noticed no heat, and gurgling sound. Pulled over, towed the car home.

Got familiar with this forum. Through the excellent descriptors and advice, I tackled the lower intake manifold and it was shot. Literally picking it apart.

Okay, so that repair sent me looking for a oil leak that was already existing.

Similar to many of the posts here, I used the trouble shooting many of you suggested. I have determined that I have a faulty oil line from the engine to the filter. Fairly straightforward fix, albeit from what others said takes some fishing of lines around the engine.

The big one that I uncovered was with the timing chain cover. It has oil leaking from the bottom of the cover. It has coated the crankshaft sensor and I suspect is the primary source of the oil leak. BTW, transmission was replaced 20,000 miles ago, and I don't know for sure but I am hoping they changed the rear main seal. I don't think this is leaking as the flex plate from the inspection hole appears clean, although their is a slight oil "weep" from the area of the main seal. Just not enough to convince me that is the source.

Here is my plan of attack to fix this issue, would like some feedback on my plan from you the experts. .

1. Remove the timing chain cover and replace with new cover/gaskets.
2. Not aware of any issues with the timing chain yet, but will inspect and replace if necessary.
3. Drop the front differential (heard it is a pain but can be done)
4. Drop the oil pan and replace gasket.

Let me know if I have it all wrong. . .

 

Someone correct me if I am wrong here....but as long as the oil pan gasket is not of the one piece style, then you should be good to go. If the one piece gasket was used and you intend to re-use it, you will need to drop the front differential first, then remove the oil pan and then remove the front cover. Otherwise you will tear the gasket apart taking the front cover off.


If you would take some pictures I know I would appreciate it as my '02 has the same oil leak from the front cover and needs to have this repair done. Or at least provide a follow-up on what you do to drop the front differential.

The timing cover will need to be replaced as it is plastic, which will mean the crank sensor will be moved which means a re-learn will need to be done.

Good luck and I will be checking back to read how this all goes.

 

My oil pan is the one piece cast aluminum style. From what I can tell there is not any play in the pan, so either you drop the pan a few inches and reuse the old gasket, or you drop the pan entirely and replace it. I am opting for the latter.

I will keep you posted as I do the tear down, and take some pics along the way.

 

Okay, pulled the harmonic balancer and timing chain cover today. Attached is a pic of the timing chain. After reading some posts, it would appear that the timing chain has already been replaced as the factor one was a roller chain.

Can anyone advise if this is true?

 

The timing chain cover itself does not use a gasket. When you get the new one from the DEALER (my opinion for this), you will see it has a sealant already in place that has the consistency similar to playdough. That's the only reason I figured why you cannot reuse the composite cover. The sealant will crush a bit when you put the cover on using the proper torque settings. Also, I would suggest you change the "O"-ring for the crankshaft position sensor.

 

I just got done replacing crank and bearings in a 97, 6 bad rod bearinga 1 spun, 2 spun mains, ate the crank - flyer with pan gasket ( warning do not use sealer on gasket install dry ) so instead of the old school way of adding sealer in at least the corners i installed dry - Yup next day i dropped the pan down to seal the corners where it was leaking - some days it pays to just do the well taught things and remember the old school teachings - IMO seal the corners, lip where timing cover sits and a inch back on the pan with black RTV - And i could be wrong but in both of the 4.3s I own both timing chains were like yours and not rollers so I don't think roller chains were factory

 

Hay Kancop First off thanks for posting this because I have to change out my timing chain. What lead to this dissension was when I had my distributor cap off there was about 10 degree+ lag from when I was turning my crank shaft back and forth.
I did check the gear at the bottom of the distributor and it looked good.
Did you end up taking your oil pan all the way off?
If any one has anything to say about this reply please let me know what you think.

 

kancop: I was referring to the oil pan gasket being one piece, not the oil pan; they are all one piece.

But you are replacing the oil pan gasket anyways, so all the better.

How far did the oil pan drop with the front differential not moved? I assume you did not drop the front diff before removing the front cover.

Anyways today I had a very small puddle of coolant under my Blazer...AAARRRGGHHHH! I have already done the upper intake gasket....now what? Will look at it tomorrow.

 

So here is my saga:

I got my gaskets for the intake manifold today, so I spent the better part of the day putting the intake back together and installing it back on the beast. Glad that is done, there were a lot of little parts that I wanted to get back together.

I am going to pull my front differential this week, so I emptied the diff, pretty dirty, then I emptied my oil pan. . . oh my. I know where my missing coolant went. It gushed out of there and then the oil. The oil didn't look to bad, other than having coolant mixed in.

With the coolant in the oil pan, are there any things I need to pay attention too that might fail as a result?

Lanny, my plan is to drop the oil pan later this week. I am going to pull my front diff to drop the pan completely. . .I need to do some work on the front suspension, but that is another thread. . .

I am tired and ready for bed. More as I get into the project!

 

The coolant eats the main bearings. The longer the coolant has been in there the higher chance the main bearings got damaged. Times that by about 10 if you were running the truck. I don't know if this is a great idea or not, so maybe someone like Captain Hook or swartlk or Rich photos can weigh in:

But if I were in your shoes, since you'll have the diff removed and the oil pan off, I'd be considering removing the main caps and rod caps for every piston (keep them in order or do it one at time). Look at the bearing in the main cap and each crank journal. Look for pitting and gouging. The crank journals for the rods should be able to tell you if the bearing on the piston rod side is damaged. I'd then use some assembly lube to put the caps back and insure they are torqued correctly.

Take it from one who knows...it's super disappointing to spend a bunch of money and then 100 or so miles down the road have your main bearings go (due to coolant previously in the oil pan). That requires an engine removal and and a either a trip to the machine shop or purchasing a new crank kit, which last time checked was around $600-700.

Once again, please wait for some of the more experienced to tell you whether what I'm thinking is a good idea or not.

EDIT: Regardless if you take the caps off or not, I would spray the **** out of the crank and bearing position with WD-40. Attempting to displace that coolant from the bearing surfaces. After everything is back together. I would probably only run the engine for 5 or 10 minutes and then drain the oil pull the filter and put more new oil in.

EDIT II: I forgot about plasti-guage like the Captain states below. If you don't already have them, I'd highly recommend you go on ebay or something like www.faxonautoliterature.com/ and get yourself the GM Technical Manuals. You have a somewhat big job in front of you and I'd want the manufacturers literature to make sure I'm doing everything correctly. Manuals will probably run you about $100 and then you have to wait for them to be delivered. For about $25 you can go on alldatadiy.com and have the e-manual for your truck along with all updates for 1 year. I have both, and find that in some cases i'm glad I have the hardcopy, and other cases I'm glad I have the online version (mainly for the search function).