Which engine gasket should I change?
 

Year: 2001
Vehicle: 2500 Suburban LT Autoride 4WD
Engine: 6.0L
Mileage: 127K

My coolant level has started dropping enough once a week to set off the Low Coolant light. It's not visibly leaking anywhere and no puddles on the garage floor.

I am noticing a white steam from the tailpipe even when the engine is warm. I also have started to notice a burnt smell from the rear of the vehicle after I take a long hill or a longer distance trip.

I have checked my oil dipstick for milky white oil, but it's normal and clean. However my Change Engine Oil light just came on, but it's only been 1,000 miles since I changed it. I usually get somewhere between 3k-4k miles after an oil change before the change engine oil light comes on.

My assumption is that I am leaking coolant into the engine and I have a bad gasket, but which gasket?

Thanks
Kevin

If you're lucky probably head gaskets- ask a garage so equipped to test the engine coolant for carbon products. If the test is positive then there is a connection somewhere between the combustion chambers and the cooling system. The problem can also be a cracked head. You will need to have the heads pressure tested to ensure that they are not the problem. A defective intake manifold gasket is less likely than a head gasket.

Changing the head gaskets can be a major expense if done at a shop, so you will need to assure yourself that the vehicle is worth spending the money on. If the head(s) are cracked, then the expense is even more extreme since you not only need to replace the head(s) but also the gaskets as well.

Hope this helps.

The water pump gaskets are famous for leaking on these engines.

Fortunately they're inexpensive,(I use hi-temp Permatex RTV on the

new gaskets as a precaution) and the Vortec water-pump is fairly easy to

access because it's no longer located under a ton of brackets and belts,

like the old L-blocks.

Thanks for the good ideas to try.

I may have access to someone with the equipment to test the coolant so I'll look into that.

I'm not sure I'm following the idea on the water pump gasket as far as how that could cause an internal coolant leak. I'm assuming if it's the pump gaskets then the water would be leaking to the outside of the engine? I'll take a closer look at the water pump, I'm not the original owner, but my guess is it's never been replaced and it might be about that time.

Thanks again!

Yeah the OEM fan clutches are real bricks.

Most name-brand replacements are much lighter, and put less stress on the

water-pump. It's all fairly inexpensive, and available at the average

large parts store.

I think that the key to your post were the references to the "white smoke" and "burnt smell". A leaking water pump gasket or seal can cause a loss of coolant but should not allow coolant into the combustion chamber.

Chevy 3.1, 3.4 and 3.8 L transverse mounted engines were notorious for blown head gaskets. Others may be as well (such as yours).

Have you checked the coolant tank for bubbles? That can be an important clue indicating a blown head gasket or cracked head. As the engine heats up and the internal pressure increases, coolant can be forced through a small crack in the head or defective head gasket into the cylinder. Combustion gases can also be forced from the cylinder into the coolant channels causing bubbles in the reservoir. This can vapor lock the cooling system and cause overheating issues.

The carbon test will tell the tale. Any rad shop could do the test for a minimum of expense. If the test is negative, the problem may be a defective intake manifold gasket.

If it turns out that the problem is the head gaskets, you could change them yourself if you are mechanically inclined. The largest problem is getting the exhaust pipes off the exhaust manifolds- the nuts are frequently rusted and a torch may be needed to remove them.

There are a number of after market products which claim to repair blown head gaskets or cracked heads without removing the heads. You might want to look at them.

Hope this helps.

Thanks 'therewolf' and 'labtek', appreciate the feedback!

Now that you mention it I think I did notice very very small bubbles in the reservoir tank when I took the cap off. I just assumed that was normal I guess, but makes complete sense now that you explained it. I'm not good at diagnosing, but I can turn a wrench!

I can do the head gaskets myself and I know what you mean on the exhaust bolts.

I'll still do the carbon test to make sure before I start tearing things apart. I'll try to remember to update the thread when all is said and done.

THANKS!

Update:

I did the carbon test on the engine coolant and there was none present. So that leaves me to believe it is not the head gaskets.

Again the oil also looks just fine. I think the Change Engine Oil light really is a mileage based thing even though the owners manual says its not. I now remember it coming on right after an oil change once before.

I'm guessing that it could the the intake manifold gasket. That would still be allowing some coolant through the system and be causing the exhaust symptoms I'm seeing.

Is there a test I can peform to determine if it is the manifold gasket?

Thanks!

Usually if an intake gasket is leaking, your antifreeze will take on a chocolate milk color. If you live near an Autozone or Advance Auto Parts, you should borrow a pressure tester in their loaner tool program and pressure test the system. You put a deposit on the tool and when you return it, you get your money back. That's where I'd start and not worry about paying someone else to try to find it.

been there
 

01burban I'm in the middle of the same issue with my 01' Silverado V6 4.3L. The intake gasket went slowly, initially probably just a few drops of coolant into a combustion chamber or two... and since the truck was used regulary it found its way out the exhaust the next day. Sometimes you could smell 'burnt coolant.' Was like this for a year, maybe longer. Then after leaving it in the garage for a few weeks while on vacation, went to start it and 'pop' - misfire. Then it just wouldn't start. Too much coolant had gotten in. Replaced the intake gasket, engine coil, cap and rotor (recommended) and it runs good, but now reading misfire on the computer and won't pass inspection. I hear you have to align the cap and rotor perfectly, so I suspect my mechanic's hands were a lilttle shakey. I don't have the tools so I think I'll just take it to a GM dealer and have them re-set the timing.