This is for NA 1994 Bonneville w/ 185k miles on it. Currently leaking oil.
I'm doing a head gasket change next week-end. If after removing
everything connected to the head and removing the head bolts, do I need
any tool to lift the head off?
Will the push rods stay or goes with the head?
Any info you guys can give, I would appreciate very much.
burnt out valve. I can tell you that no real special tools are needed, but
a whole lot work & patience sure is! Just about everything has to either be
disconnected or taken out of the engine compartment to get those darn heads
off too! Plus, the old head bolts are NOT reuseable either!
As for common oil leaks, it's usually just the lower intake manifold or
valve cover gaskets that leak oil though. The head gasket when fails
usually leaks coolant.
Sincerely, Alan Ralston
GM Partsman for a Pontiac Dealership
I have a Montana 2000 which I bought at an auction a year ago. I notice I
was low on coolant in the reservoir. Then I opened the rad cap and it is
full, but it has some kind of chunks floating in the coolant. There is a
warning on the reservoir not to fill it with just any type of coolant.
Can I add a bit or regular green/ yellow coolant or even some water? Any
reason why I would want to flush the system. I have been told that the
chucks could mean the rad had a leak before and sealer was added to seal the
leak. Also the coolant really stinks, a real bad smell to it. Any
advise. Should I add any coolant at all? There still is a little bit of
coolant in the reservoir. And as far as I can tell, the van has never
over heated before.
Never mix green antifreeze with the pink stuff. Whatever you do, flush the
system and replace the coolant with 50/50 mix of distilled water and regular
green antifreeze. The pink stuff is causing problems in lots of cars.
My suggestion is to have the system flushed and refilled with Dexcool, which
is what it left the factory with and what GM recommends. The vehicle was
designed with Dexcool in mind - not the green stuff. In my opinion, Dexcool
works just fine in vehicles designed for it, such as your Montana. Just keep
a very close eye on the coolant level. Dexcool seems less tolerant of air in
the system than the "green stuff". It is likely there was/is a leak in the
system that was/needs to be repaired. Most complaints I've seen or heard
about Dexcool fall under three categories:
1. Not maintaining proper coolant level, thus allowing air into the system.
2. Mixing other coolant types with Dexcool.
3. Using Dexcool in an engine not designed for it.
The "chucks" are tablets that come from the factory to help seal minor
leaks. Dexcool does not have that same ability as the only green
antifreeze. In fact if you take it to the dealer to have the system
flushed, they will add more tablets to your cooling system.
Look around the water pump and intake gaskets for signs of antifreeze. That
could be your leak. If you are going to get your system flushed, do not go
to a dealership. Go to someone where they will not reinsert the tablets.
Hope this helps.
To me it sounds like cylinder 6 is running lean. This would make for a very
hot cylinder and could have melted off the electrodes from the spark plug.
Possible causes: clogged injector, bad intake gasket (these engine are
notorious for them), burnt valve. I would get this problem solved ASAP so
you don't cause serious engine damage.
Which O2 sensor was showing the leak? You car does have more than one. IT
has one before the converter and after. If it is the O2 before the
converter check the exhaust gasket between the pipe and the manifold to make
sure that it is not leaking. This will also cause a lean condition, and
possibly a faulty O2 sensor reading.
I asked the mechanic again what exactly did the scanner read. He said the
left bank reading was lean. He also mentioned that cylinder 6 is miss
firing (I assume that the left bank is cylinder 2,4, and 6). I replaced
the 6th cylinder spark plug. And at first it seamed that starting the
van was a lot easier. But next day engine light was back on and it takes
about 5 tries before the ignition starts. Question can ignition problems
have anything to with this lean reading. Can it be related to the miss
firing problem? If so, If so difficulty starting especially in the
mornings, does that give you a clue if it could have something to do with a
bad sensor as opposed to miss firing problem? I would like to address the
mostly likely problem first or the easiest solution first.
btw: I year ago I had sugar in the gas tank, so I had the tank replaced.
And added some fuel injection cleaner in the gasoline. I have had no
Ahhh, a lean condition, that makes more sense than a "O2 leak".
Left bank is 1,3,5. A misfire on six should cause a rich condition on right
bank which the computer could misinterpret as lean on the left.
After having it fixed the light came on again.....that doesn't mean the same
trouble code is reset. Could be something else this time.
An injector sticking can cause a lean condition.
My engine light is one so my mechanic scanned and found an oxygen leak in
the exaust. What can cause that? for the full story read the following
I have a venture van 2000 and recently got an misfire code that was read at
the mechanics shop. Also, scanner detected an O2 leek. The cleared the
error message and (June 25th) I change the spark plug for that 6th cylinder.
I notices the nipple circle on the top hook of the spark plug was totally
gone. I checked a different plug and the nipple was fine on that one.
Also to mention that we had problems starting the ignition on the first try
(sometimes takes 5 tires). Now that I put a new spark plug it starts like
a beauty. I had the engine light come up before (5 months ago) and
mechanic found a O2 leak. But did not mention a miss fire problem. That
time he cleared it and it was fine until a week ago. So now I want to
figure out why I had this problem so it does not happen again. My
warranty just ran out and will be selling the van this summer. I would
appreciate any additional insight as to what the root cause of this problem.
Could a miss fire cause O2 leak? Or did the o2 leak caused the miss
fire, leading to worn out spark plug? I have about 50,000 km (about
30,000 miles). What do you think? Thanks.
I have driven it some more today and now the engine light is on again, after
changing the spark plug.
If this is in the US, take it back to the dealer. The emissions warranty is
over 36,000 mi (I think it is something like 80,000 mi). Not sure about
other countries though. Look in your warranty materials.
You probably have an internal coolant leak inside your engine. The
coolant is escaping into the combustion chamber or crankcase through
cracks in the cylinder head or block, or through a leaky head gasket.
In rare instances, coolant may also leak into the automatic transmission
fluid cooler if one is located inside the radiator. But usually when
automatic transmission fluid leaks into the coolant it means the line is
Pressure testing the cooling system is necessary to diagnose an internal
leak. A cylinder leak-down test can tell a mechanic if the coolant leak
is in the combustion chamber. But to pinpoint an internal leak, it is
usually necessary to remove the head(s) from the engine. The head may
then be pressure tested and/or checked for cracks using special
Minor internal leaks can sometimes be temporarily sealed by adding a
sealer to the cooling system. But large leaks or ones that do not
respond to a sealer will have to be fixed.
If the problem is a cracked head or block, repairs may or may not be
possible depending on the nature of the crack. Cracks in aluminum can
often be repaired by welding while those in cast iron can be fixed by
pinning the damaged area. But some cracks may be so bad that they are
beyond repair or in a location that makes repair impossible. In such
cases, the head or block must be replaced.
If a leaky head gasket is the culprit, replacing the gasket may only
temporarily cure the problem if the head or block is warped. The mating
surfaces on both the head and block should be checked for flatness and
resurfaced if necessary to restore flatness for a proper seal.
Hope this shed some light for you.
00 VX SS 273 Rwkw of unforced mumbo.
Thanks Dan ... I was also thinking along the same lines, leakage into the engine
combustion chambers ... but I always thought that would lead to visible "smoke"
exhaust ... we're not seeing any of that either.
Having said that, do you still think most likely it's leaking inside the engine?
it must be if there's no other (outward) sign of loss, huh?
Thanks ... Phil
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