Got a 2001 Monte Carlo SS (3800 V6).
What would cause the engine coolant to become dirty? I noticed some
"sludge" (for lack of a better term) around the top of the radiator
cap the other day and immediately had the coolant flushed and filled
when I had Jiffy Lube change my oil.
Is dirty coolant a normal occurance, and is a flush/fill a proper way
to address the issue, or is this a sign of serious problems to come?
Thanks for any info.
Yours is a 3800 series II engine, I believe. People here will correct me
if I am
wrong, but you know the inherent issues with the decomposing FI plenums on
these engines, dont you? (When ours went bad, water went into the
but bear in mind that if you have a plenum failure, or head gasket, or a
strange and unpleasant things can happen.)
Assuming your engine is sound, antifreeze does, eventually, deteriorate,
Dexcool crap. It should be flushed out and replaced with a good antifreeze
at recommended intervals (or before). IF your system is not functioning
and you get an air leak into the coolant, corrosion will start sooner and
severe than you might think. Rusting iron plays a number with antifreeze,
particularly with the Dexcool crap, which is based on organic
acids form salts with iron which are nasty, goopy, ugly.
You might want to do a little diagnosis or detective work and not just
that a flush will bring you back to health. That could be all it is, but it
signs of other things going on.
Up to milage in the mid 50K's I know for sure there was Dex-Cool in
the system - because it was the original stuff. Then I had it flushed
and filled (I know that's way earlier than needed, but it's a long
story having to do with NTB stripping the threading on my radiator
when doing a transmission fluid flush/fill, and then them paying for a
new radiator for me). I *believe* when the new radiator was installed
the mechanic put in traditional antifreeze due to concerns that Dex-
Cool apparantly eats away at the head gasket (I could be wrong, and
need to double check my paperwork). So from milage mid 55K to
recently (120K), I didn't worry too mauch about it, until a low
coolant indicator turn on. That's when I noticed the dirt buildup
around the radiator cap. After my most recent flush/fill (few weeks
ago) there is dex-cool in the system.
So if I understand that link posted earlier, one culprit for the
contamination may be a faulty radiator cap?
"The culprit: low coolant! All vehicles that showed contaminated
cooling systems shared one common condition: low coolant. Low coolant
level in the radiator allows a beachhead type of deposit
accumulation in much the same way that ocean waves deposit sand on the
beach. This material can collect on the drop-center valve at the
bottom of the radiator cap and prevent it from sealing. Without that
seal, the coolant boiling temperature is reduced to 226°F. Sealed to
15 psi, it will not boil before 265°F. The lack of pressure and
premature boiling allow an already under filled coolant reservoir to
completely empty itself and leave the radiator tank with a substantial
air pocket or beachhead. Always test the pressure cap and replace it
if it fails to hold proper pressure."
I have a feeling that it would be prudent for me to take the thing to
a professional to have it looked at.
After my most recent flush/fill (few weeks ago) there is dex-cool in the
Dexcool is not the panacea many would believe. The early versions were
Essentially ALL the good and premium quality antifreezes on the shelves
are totally compatible with Dexcool.
I dont believe your problem came from having Dexcool in the system, and
not from having the radiator flushed and replaced with another good or
brand of antifreeze.
It is still somewhat in question whether Dexcool damaged gaskets, or whether
poor quality of gaskets that GM used were the bigger part of the problem.
were a lot of rumors about Dexcool, not all of them founded in fact.
It is not in doubt that the GM series II 3800 engines had a prone to fail
fuel injection plenum, and that the gaskets that GM used were also prone to
In those engines, I believe it is not a matter of whether the plenum will
fail, but when
it will fail. The gaskets are, IMO, somewhat less of a problem, although I
some of those engines with relatively low age and mileage and have seen some
You problem might have nothing to do with gaskets or plenum. That is why I
a bit of detective work first. A really good mechanic -not necessarily a
dealership mechanic -
should have the experience and equipment to avoid a lot of trial and error.
I hope you will tell us how this finally plays out.
Besides the old news about Dexcool damaging cooling systems and
engines (see: http://www.consumeraffairs.com/news04/2006/08/gm_dexcool.html ),
air in the system, tap water, and mixing coolants (prior to Dexcool
compatible formulas all over the market these days) were not good
If the radiator cap's vacuum valve was plugged, then you would
probably see collapsed radiator hoses. As soon as you remove the cap,
air would rush back in and they swell back up.
If you see bubbles in the reservoir when hot, then the head gasket may
Sure, get a competent cooling system shop to look at it.
I finally took the car to the shop, to a guy I trust, and it turns out
the lower intake manifold gasket had failed. So, I had that replaced,
along with the upper gasket, valve cover gaskets, spark plug wires
(127K miles) along with some other minor stuff. I think it might be
time to look for a replacement car (hoping that I can have this one
last 6-8 more months to get milage out of this repair!).
Unless there are other problems, there is no reason to believe it won't be
worth running longer. The intake gasket problem is very well documented,
and your replacement should gain you many thousands of miles of life out of
the car. If you like the car and other aspects of the car seem to be in
good shape, then press on and enjoy the car.
Listen to Mike. I agree, cars are just nuts and bolts. Keep the
repairs up, rust down and drive 'em. A car only is unusable when
you decide not to maintain it anymore. Change the fluids and filters
on time, regular.
Mike Marlow wrote:
A website is a place, where, when you go there, it does everything
possible to distract you, from finding the information you came there
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