can intake manifold gasket leak cause bad mileage?

I have a car with dex-cool (Buick Century 2002 3.1 V6). The car has been
driven very little and has only 15K miles on it. Not a typo, that's fifteen
thousand miles in a 2002.

No work has been done recently. No engine work ever, AFAIK.

Last fall I noticed that my mileage had dropped from 23/33 to 14/27 mpg.

Last week, I lifted the hood to see if I could spot any loose or broken vacuum
lines, and I noticed that the lid of the coolant reservoir was off. The
reservoir was empty - I don't know if it had evaporated out the top, or if
there is a leak.

I have good power when I step on the gas. No odd noises. I haven't spotted any
leak. But I'm in the northeast and haven't been looking much, seeing as how
it's winter.

I just became aware of how dexcool can cause the Lower Intake Manifold gasket
to fail, and the now-expired class action suit. I don't suppose there's any
way to know what percent of 2002 Century will fail.


And btw, how do I get the LIM checked? Would any mechanic have a simple/easy
check that they would do for free? Thanks.

Tom wrote:
> I have a car with dex-cool (Buick Century 2002 3.1 V6). The car has been
> driven very little and has only 15K miles on it. Not a typo, that's fifteen
> thousand miles in a 2002.
>
> No work has been done recently. No engine work ever, AFAIK.
>
> Last fall I noticed that my mileage had dropped from 23/33 to 14/27 mpg.
>
> Last week, I lifted the hood to see if I could spot any loose or broken vacuum
> lines, and I noticed that the lid of the coolant reservoir was off. The
> reservoir was empty - I don't know if it had evaporated out the top, or if
> there is a leak.
>
> I have good power when I step on the gas. No odd noises. I haven't spotted any
> leak. But I'm in the northeast and haven't been looking much, seeing as how
> it's winter.
>
> I just became aware of how dexcool can cause the Lower Intake Manifold gasket
> to fail, and the now-expired class action suit. I don't suppose there's any
> way to know what percent of 2002 Century will fail.
>
>
> And btw, how do I get the LIM checked? Would any mechanic have a simple/easy
> check that they would do for free? Thanks.

holy cow, on closer look: what I'd thought was a low level of coolant on this
slim-style reservoir is actually right on the 'Cold' line. The reservoir
should be mostly empty, with just a few inches of coolant on the bottom. The
coolant in there looks dark, but not thick. The radiator cap is clean, and
there is only a bit of sludginess floating on top of the visible coolant.
That's good news.

Also, the engine oil itself is not milky, and the level is not overfilled (so
coolant had apparently not gotten into the oil).

So I guess I should go with a flush and fill. But should I use Dexcool or
switch to something else like the Prestone Long Life? I've read about that for
hours yesterday and there doesn't seem to be a conclusive answer.

One big question occurs to me: do I not have a problem at this point because
of the low miles (15K)? If so, why don't the years matter (since late 2002)?

Also, I still have the problem of the sudden reduction in mileage...

In article >, Tom > wrote:
>
>And btw, how do I get the LIM checked? Would any mechanic have a simple/easy
>check that they would do for free? Thanks.

Have a competent tech plug a scanning tool in and look at the fuel injection
parameters... if something is leaking on the intake, it'll show up with some
goofy numbers.

A can of WD-40 or an unlit propane torch can help find the problem.... if
you get it near the leak and it sucks it in, the engine will race.

I doubt anyone will do anything for free today, and I wouldn't trust anyone
who did. If they're not charging you anything for diagnosis, they're damn
sure going to find _something_ to charge you for.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article >, Tom > wrote:
>So I guess I should go with a flush and fill. But should I use Dexcool or
>switch to something else like the Prestone Long Life? I've read about that for
>hours yesterday and there doesn't seem to be a conclusive answer.

If it's not broken, don't fix it.

If you haven't had any problems with the DexCool (and I'm surprised you
haven't because everyone else pretty much has), keep using it and don't
change it.

If it has never been flushed in eight years, it's way overdue. I'd consider
brake and maybe even transmission fluid too.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Fri, 19 Feb 2010 09:43:12 -0500, Tom > wrote:

>Tom wrote:
>> I have a car with dex-cool (Buick Century 2002 3.1 V6). The car has been
>> driven very little and has only 15K miles on it. Not a typo, that's fifteen
>> thousand miles in a 2002.
>>
>> No work has been done recently. No engine work ever, AFAIK.
>>
>> Last fall I noticed that my mileage had dropped from 23/33 to 14/27 mpg.
>>
How are you measuring that? Are you sure?

>> Last week, I lifted the hood to see if I could spot any loose or broken vacuum
>> lines, and I noticed that the lid of the coolant reservoir was off. The
>> reservoir was empty - I don't know if it had evaporated out the top, or if
>> there is a leak.
>>
>> I have good power when I step on the gas. No odd noises. I haven't spotted any
>> leak. But I'm in the northeast and haven't been looking much, seeing as how
>> it's winter.
>>
>> I just became aware of how dexcool can cause the Lower Intake Manifold gasket
>> to fail, and the now-expired class action suit. I don't suppose there's any
>> way to know what percent of 2002 Century will fail.
>>
>>
>> And btw, how do I get the LIM checked? Would any mechanic have a simple/easy
>> check that they would do for free? Thanks.
>
>holy cow, on closer look: what I'd thought was a low level of coolant on this
>slim-style reservoir is actually right on the 'Cold' line. The reservoir
>should be mostly empty, with just a few inches of coolant on the bottom. The
>coolant in there looks dark, but not thick. The radiator cap is clean, and
>there is only a bit of sludginess floating on top of the visible coolant.
>That's good news.
>
>Also, the engine oil itself is not milky, and the level is not overfilled (so
>coolant had apparently not gotten into the oil).
>
>So I guess I should go with a flush and fill. But should I use Dexcool or
>switch to something else like the Prestone Long Life? I've read about that for
>hours yesterday and there doesn't seem to be a conclusive answer.
>
>One big question occurs to me: do I not have a problem at this point because
>of the low miles (15K)? If so, why don't the years matter (since late 2002)?
>
I don't know about the Dexcool because I've avoided it, and heard it
causes problems. But I've read that turbulence has some effect, so
the more miles the more turbulence.
My '97 Lumina 3.1 had Dexcool in it when I bought it with 105k miles.
Now has 150k miles. Here's what I did when I bought it.
I drained the Dexcool out by pulling the lower rad hose. Put hose
back, filled with water and ran it hot for a while. Think I opened
the rad petcock and used a garden hose to keep it topped off for a
while. Didn't get too anal about it. When there was no yellow left I
was done.
Pulled hose again to drain, then put on new hoses and thermostat.
Filled with a 50/50 of the Prestone green stuff, and added a pack of
the GM cooling system sealant pellets.
5 years ago. So far so good.

>Also, I still have the problem of the sudden reduction in mileage...
>
First make sure your milage check is accurate.
32mpg is near tops for highway on mine. I never checked city closely
- too many variables. Seem to get around 18-20.
You might have a miss somewhere, or a bad injector.
Hard to tell. If they are original plugs/wires you should replace
them. I'd do the wires first. Plugs might be fine.
Might be worth it to have a mech hook it to a diag machine.
Eliminate the guesswork.

--Vic

ps Sorry I sent a reply to your e-mail.

Tom wrote:
> holy cow, on closer look: what I'd thought was a low level of coolant on this
> slim-style reservoir is actually right on the 'Cold' line. The reservoir
> should be mostly empty, with just a few inches of coolant on the bottom. The
> coolant in there looks dark, but not thick. The radiator cap is clean, and
> there is only a bit of sludginess floating on top of the visible coolant.
> That's good news.
>
> Also, the engine oil itself is not milky, and the level is not overfilled (so
> coolant had apparently not gotten into the oil).
>
> So I guess I should go with a flush and fill. But should I use Dexcool or
> switch to something else like the Prestone Long Life? I've read about that for
> hours yesterday and there doesn't seem to be a conclusive answer.
>
> One big question occurs to me: do I not have a problem at this point because
> of the low miles (15K)? If so, why don't the years matter (since late 2002)?
>
> Also, I still have the problem of the sudden reduction in mileage...
>

The problem in the mileage reduction could be due to a LOT of things.
Sitting that long the interior of the muffler could be rotted and
blocking the system, Mouse may nave gotten to the wiring and caused
problems. Fuel lines may have developed a leak due to rust. Injectors
may be clogged due to crap in the fuel lines from sitting.

Low mileage is NOT really a good thing sometimes.

As for the Dexcool. Change it out and flush the system and put in fresh
coolant. The bad rap that Dex gets is NOT due to the coolant itself. It
was due to how it was marketed by GM. They claimed it was a lifetime
coolant when it really isn't. It still needs to be changed out and the
system flushed every 4-5 years to prevent problems.

Personally I use the universal type coolant Prestone sells. Then just
note that it will need a flush and fill in 3 years. When you look at
what it costs to do a flush and fill versus what it costs to replace
plugged or damaged parts it's REALLY cheap...

Oh and my usual routine on my vehicles is to drop the coolant, flush the
system. Then while clean water is in the system, pressure test it for
leaks. Drain everything including the block. Then change the thermostat
and the water pump out, inspect the hoses close and every second flush
replace them, new serpentine belt as well.
Being that I keep vehicles a LONG time this is just cost of ownership.

--
Steve W.

Prestone and Bar's Leaks.That is what I always use.
http://www.prestone.com
http://www.barsproducts.com
cuhulin

Tom wrote:

>
> So I guess I should go with a flush and fill. But should I use Dexcool or
> switch to something else like the Prestone Long Life?

Prestone long life and Preston "all makes all models" are just DexCool
clones and contain the same chemical (2EHA) that is in DexCool and
softens intake gaskets.

If you want to be really safe, you should have the lower intake gaskets
replaced anyway. DexCool has already attacked them, and from my reading
I gather that they tend to fail on those engines eventually pretty much
no matter what.

As for alternative coolants, G-05 seems to be the best/safest
alternative to DexCool. Zerex sells it (gold bottle- sometimes hard to
find) and you can get it from any Ford dealer (Motorcraft Premium Gold)
or from any Chrysler dealer (Mopar G-05, which is dyed red instead of
gold like Zerex and Motorcraft). I also hear good things about Peak
Global Lifetime coolant. You could also use old-style conventional
silicated coolant and change it every 2 years like the old days. But it
is getting very hard to find now also.

wrote:
> Prestone and Bar's Leaks.That is what I always use.
> http://www.prestone.com


You do realize that Prestone completely changed formulas a few years
ago, right? They don't make a conventional coolant any more, only their
"all makes all models" coolant, and it is a clone of DexCool.

I always change the radiator fluid once each year.Usually just before
Wintertime.Years ago, some people used to change radiator fluid twice
each year.For Summer time and Winter time.
cuhulin