2002 w/ 3100 - losing coolant, and lots of sludge

A friend of mine has a 2002 Century with a 3100 engine, 65,000 miles. The car has been well cared for, with all regular maintenance performed on time.

The car is losing coolant, the low coolant sensor comes on every few hundred miles. The local garage has added coolant, replaced the coolant sensor :screwy:, and flushed the entire system. At this point my friend asked me to have a look.

1) Slimey "milkshake" on oil cap. Cleaned & dried it 4 days ago. 100 miles later, it's all slimey again.
2) Rad cap also has slimey gunk on it.
3) Coolant recovery tank is CRUDDY. The walls are all darkened with what I'd assume is oil residue.

Now, before anyone starts saying this is normal with Dexcool, I'll mention that I have a '98 and an '02 Grand Prix with Dexcool, they have 218,000 and 158,000 miles, respectively. My oil caps are bone dry. My coolant caps have only Dexcool on them. And my coolant recovery tanks are so clean they look new.

In seems to me that there is some kind of internal issue, e.g. intake manifold gasket, where the fluids are mixing. FWIW, I don't see any sign of external coolant leakage.

Do the 3100s have any known issues in this area?

I suggested my friend have the Buick dealer pressure test it (when it's cold), and go from there.

Whatya think?

3100s have both intake and head gasket issues. Usually only the head gasket problems if the intake problems have been neglected. If you're just going to do the intake gaskets (the lowers are the problem area) it's a one night project. Just make sure you buy the new fel-pro gaskets which are metal instead of the old hard plastic versions. I don't have a part number handy, but any knowledgeable parts guy would know what you're talking about.

I suggest that you forget the pressure test, stop driving the vehicle and change the lower intake manifold gaskets. If you continue to drive the car you are going to damage the bearings and you will need a complete rebuild. The sludge is being caused by the water getting in the oil and the only way to eliminate the problem is to replace the gaskets. Felpro gaskets are the ones to use and it will take about 8 hours to complete.

I suggest that you forget the pressure test, stop driving the vehicle and change the lower intake manifold gaskets. If you continue to drive the car you are going to damage the bearings and you will need a complete rebuild. The sludge is being caused by the water getting in the oil and the only way to eliminate the problem is to replace the gaskets. Felpro gaskets are the ones to use and it will take about 8 hours to complete.

That's pretty much what I was thinking. I don't know if you remember me, but I did the UIM/LIM job on my son's 97 Grand Prix 10 days ago, I was over in the GP forums and read some of your posts.

Sure do! The Buicks suffer from similar problems since they use the same cheap GM gaskets. Since you did one on the Grand Prix you shouldn't have any issues with this one. Although make sure to keep the push rods in correct order. The intake and exhaust are different as the way the intake manifold mounts to the engine. The section in the Grand Prix manual on the 3.1 should work fine for the Buick.

I called the dealer on behalf of my friend, explained the problem, and the dealer said bring it in. The dealer looked it over and called back today - they said not only is the intake manifold leaking, but so are the head gaskets. They quoted $1,669 to do the repair. Mother of Troy!

Next I had my friend call Buick corporate, and in a very friendly, sincere way, explain what's going on. The call was escalated to the next level, and then the advisor said they would call the dealership and discuss the condition of the car and get back to him.

It will be interesting to see what Buick does for a customer who's purchased three Buick Centuries in the last 15 years.

If they do anything for you I would be very surprised. I wouldn't count my savings just yet. You can do this for about 1/4 the cost but it will take time. Let us know if you need some additional assistance as everyone will be glad to help out.

As it stands, Buick has asked to see the service records for the car to verify it's been properly cared for. It has been, my friends are gathering the records now. This repair is out of my league in terms of time involved, etc. I suspect Buick will kick in 1/2 for the repair. Pontiac did this once for my mother, her tranny went out of warranty. Long story, but they were good about it.

My friends traded in their leaky Buick - good riddance! They bought a 2007 LaCrosse. Wow, what loyal customers they are!

:banghead: Maybe someone can help me along these lines. My ' 96 seems to be doing the same thing. Naturally I bought it used. Are these gaskets something that can be replaced by someone with medium auto experience?
Im beside myself, as this car replaced my ' 91 Sunbird that the head cracked on...... I'm wondering if the GM gods have it out for me.

I did the job on a 97 GP with the 3800 engine. I replaced both upper & lower gaskets. I'd say have have "medium" experience also. Taking my time, it took me about 6 hours.

From what I understand, the job is more involved on a 3100 engine. Do research on "intake" "manifold" and "gasket" on the forums. The Grand Prix forum has a lot of info over there, too, and some of the GPs have the 3100 engine.

This is a relatively easy job to do if you have basic machanical knowledge. I would purchase a Chiltons manual as it goes into more detail than the Haynes manual on this replacement. A factory service manual is really the best but they are expensive.

As guitarfish pointed out we have several threads on doing an LIM job on the GM 3100 60 degree engine. Here is a good one at Pontiac Grand Prix.

Click here (http://www.automotiveforums.com/vbulletin/showthread.php?t=526875&highlight=intake+manifold)

The procedure in the link is applicable to GM cars with the VIN "M" 3100 engine. 2000 and up models have the VIN "J" and there are some minor differences. What makes the 3100 LIM job more tedious than for a SII 3800 is the fact that you must remove the valve covers and screw with 3 pushrods on each bank. They must be removed to remove the LIM and therefore, proper rocker arm adjustment is required during reassembly.

BTW - The VIN "J" 3100s have a new torqueing procedure on the LIM bolts both pattern and torque value. There are revised LIM gaskets that GM introduced back in later 2002-2003.


Engine Oil or Coolant Leak (Install New Intake
Manifold Gasket) # 03-06-01-010B - (10/24/2003)


Engine Oil or Coolant Leak (Install New Intake Manifold Gasket)

2000-2003 Buick Century

2002-2003 Buick Rendezvous

1996 Chevrolet Lumina APV

1997-2003 Chevrolet Venture

1999-2001 Chevrolet Lumina

1999-2003 Chevrolet Malibu, Monte Carlo

2000-2003 Chevrolet Impala

1996-2003 Oldsmobile Silhouette

1999 Oldsmobile Cutlass

1999-2003 Oldsmobile Alero

1996-1999 Pontiac Trans Sport

1999-2003 Pontiac Grand Am, Montana

2000-2003 Pontiac Grand Prix

2001-2003 Pontiac Aztek

with 3.1L or 3.4L V-6 Engine (VINs J, E - RPOs LG8, LA1)

This bulletin is being revised to change the model Information. Please discard Corporate Bulletin Number 03-06-01-O10A (Section 06 - Engine).


Condition

Some owners may comment on an apparent oil or coolant leak. Additionally, the comments may range from spots on the driveway to having to add fluids.

Cause

Intake manifold may be leaking allowing coolant, oil or both to leak from the engine.

Correction

Install a new design intake manifold gasket. The material used in the gasket has been changed in order to improve the sealing qualities of the gasket. When replacing the gasket, the intake manifold bolts must also be replaced and torqued to a revised specification. The new bolts will come with a pre-applied threadlocker on them.

Notice

An oil leak may result if the vertical bolts are not tightened before the diagonal bolts.


Diagonal bolts may require a crows foot to tighten.

Tighten

1. Tighten the vertical lower intake manifold bolts (1) to 7 N.m (62 lb in).

2. Tighten the diagonal lower intake manifold bolts (2) to 7 N.m (62 lb in).

3. Tighten the vertical lower intake manifold bolts (1) to 13 N.m (115 lb in).

4. Tighten the diagonal lower intake manifold bolts (2) to 25 N.m (18 lb ft).

This might help too. (http://dtips.no-ip.org/General/Articles/Content/Article10.aspx)

^^^Neat article with pictures.

If you get the $85 felpro kit it comes withupper and lower intake gaskets, valve cover gaskets, a crappy little bit of black RTV, a new o-ring seal for the oil pump drive gear, and a new thermostat seal - not a bad idea to pop in a new 'stat and that o-ring while you have the LIM pulled.

Pick up a Haynes/Chilton manual for your vehicle, then get to work.

Take your time, keep everything clean and in order and you'll be fine.

To keep yourself confident in the procedure, number both sides of every connection as you go - then count backwards to put it al together.
-use plastic baggies to label loose nuts and bolts.
-take notes and pictures to help puttin' it back together.

If you catch a snag let us know and we'll help you through it ASAP.

-Mark T. e-mail me if you need it. (thelstcause@yahoo.com)

I have a 2002 Buick Century Limited. It has 20,000 miles on it. I have always kept the car in good shape and didnt even use it that much. Recently I was driving locally and the temp light came on and the temp gage was on H. I looked in the coolant tank and it was brown and sludgy. I took it to the mechanic and he said that oil and coolant had mixed and that I needed to replace the head gaskets and the intake manifold and the job would cost $1,600. I read that there is a manufacturer problem with these cars (regarding Dex Cool and the intake manifold, if this is indeed what initially caused it) and I was wondering if anyone had the same issue and had it fixed and the problem came back? I guess my concern is: should I put the money into it only to find that the bad oil went into other parts of the engine or other areas of the car or should i just start new and put the money towards a new car and start over? Once this problem is fixed will i see more problems related to it down the road? Is it ever really fixed? Let me add that the temp light never came on before this and there was no smoke and the engine wasnt even really that hot. I went from having a perfectly good car, to no car at all! Any advice would be helpful! Thank you.

I have a 2002 Buick Century Limited...
Welcome. You should start a new thread, not resurrect an old one that is 7 years old.

Now to your question - the repair, if done correctly, will correct the factory flaw. Whether it's worth $1,600 - that's for you to decide. All the best...

Ok I will start a new thread. Thank you for your response.
So you are saying, if there are no other issues with it, its my preference: new car or not? But I will not see this problem anymore?

Thanks!

How do you start a new thread?

I have a 2002 Buick Century Limited. It has 20,000 miles on it. I have always kept the car in good shape and didnt even use it that much. Recently I was driving locally and the temp light came on and the temp gage was on H. I looked in the coolant tank and it was brown and sludgy. I took it to the mechanic and he said that oil and coolant had mixed and that I needed to replace the head gaskets and the intake manifold and the job would cost $1,600. I read that there is a manufacturer problem with these cars (regarding Dex Cool and the intake manifold, if this is indeed what initially caused it) and I was wondering if anyone had the same issue and had it fixed and the problem came back? I guess my concern is: should I put the money into it only to find that the bad oil went into other parts of the engine or other areas of the car or should i just start new and put the money towards a new car and start over? Once this problem is fixed will i see more problems related to it down the road? Is it ever really fixed? Let me add that the temp light never came on before this and there was no smoke and the engine wasnt even really that hot. I went from having a perfectly good car, to no car at all! Any advice would be helpful! Thank you.
I've had issues with my similar cars. You have only 20K miles on your car. I would fix it and keep it. The problem was a bad intake manifold gasket design. The ones that will be put on should be a correction and you should not have the issue again. However, it depends on how competent the mechanic is. Also, was there a water/oil mix in your crank case for very long? Did it overheat? Only you could best answer these questions.

So, this "mechanic" looked at this vehicle, and decided both head gaskets needed replacement? Did he do any tests, or was this just an observation of the "stuff" in the reservoir? Was the oil on the dipstick brown? Was the reservoir empty? I believe the level sensor is in the radiator....was the level in the radiator ok? When removing the cap, you will probably find crud on the bottom of it.....that is what happens when dexcool and air start to mix.....If the level is ok in the radiator, that sensor is probably slimed up and has to be replaced, and the coolant flushed(that coolant should be flushed as part of the head or lower intake job)......

You say you do regular maintenance.....oil changes every 3,000 miles? How many miles since your last oil change?

Your car is 13 years old....that coolant should have been flushed at least twice by now.....

If the mechanic just looked at the reservoir, without doing any tests, I would get a second opinion......

That reservoir, will get a brownish build up over the course of 13 years without a flush.....

You have lost coolant......but you don't know where, without testing......for all you know, it could be a weeping water pump, or leaking radiator or hoses, etc.....

Whenever you lose coolant, you create an air pocket which will restrict coolant flow through the engine and cause it to overheat......

More than likely, you have probably have a lower intake leak, which is about half the cost of what you were quoted....

So what I would do, is get an oil change....flush out that reservoir, have the system "burped" of all air, and then check the lower intake for leaks......If heads are suspected, then the vehicle should be tested for a head leak.....

Whether it's lower intake or a head job, the coolant should be flushed, oil changed, thermostat replaced, and dummy distributor shaft seal and o-ring replaced....

Now, before anyone starts saying this is normal with Dexcool, I'll mention that I have a '98 and an '02 Grand Prix with Dexcool, they have 218,000 and 158,000 miles, respectively. My oil caps are bone dry. My coolant caps have only Dexcool on them. And my coolant recovery tanks are so clean they look new.

Do the 3100s have any known issues in this area? Whatya think?


I know a guy who got in an accident and wasn't wearing a seat belt. He came out good. This doesn't mean not wearing a belt is no problem.

Same as Dexcool. Just because you have a couple cars that haven't had a problem, doesn't mean nothings wrong with dexcool.

Chris.

I know a guy who got in an accident and wasn't wearing a seat belt. He came out good. This doesn't mean not wearing a belt is no problem.

Same as Dexcool. Just because you have a couple cars that haven't had a problem, doesn't mean nothings wrong with dexcool.

Chris.

Necropost much? You quoted something I wrote NINE years ago, lol. But FWIW, since then, I added a couple more Grand Prixs to the stable, all of which are pushing 200K miles, with that gorgeous orange DexCool, nary a problem.

Doesn't much matter to me know though, I only have one Prix left, and it's gonna be traded in another couple years.