Coolant Leaking Into Engine Oil


pretty bad
Typical Repair Cost:
Average Mileage:
89,100 miles
Total Complaints:
9 complaints

Most Common Solutions:

  1. replaced head and intake gaskets (8 reports)
  2. not sure (1 reports)
2003 Pontiac Montana engine problems

engine problem

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2003 Pontiac Montana Owner Comments

problem #9

Apr 282012

Montana 3.4L V6

  • Automatic transmission
  • 187,654 miles


Replaced intake gasket, Dealer said see you in few miles for head gasket and sure enough the head gasket went. I believe because it was disturbed because of faulty intake that this made head gasket go. If not, I am not sure why mechanic knew I would be back. Can’t sell vehicle to anyone I don’t want to create a enemy. Stuck between rock and hard place van has been what we need but repair of this magnitude not in the cards.

- kmontana, Brandon, MB, canada

problem #8

Jun 232010

Montana 3.4L

  • Automatic transmission
  • 127,221 miles

127,000 miles on a 2003 Pontial Montana, I guess I can't complain but a "PLASTIC" intake manifold gasket??? The backyard fixit man has had (like me) 2 Montana's and knows well about the problem. Fortunately he knew about a metal gasket now available and should not be a problem again. While he is at it (taking about half the engine apart) he is going to do a major tune up (replace spark plugs, etc) for another $200 which is included in the $900 total repair. Plastic door knobs is one thing and even on the radio but for the engine? Come on GM; get your act together. Of course you not making the Montana anymore so I guess I have to give Ford a try.

- sorah, Kingsport, TN, US

problem #7

Jan 012008


  • Automatic transmission
  • 38,000 miles

Had similar problem with my 1999 Montana. Both incidents run over $1000. Mechanic told me when I paid that he will see me in about 40000 miles ( Have not got they yet,but hope he was kidding)

- dtvander, Portage, MI, US

problem #6

Apr 162007

Montana 3.2L

  • Automatic transmission
  • 113,000 miles


The really bad thing was that they used plastic for the intake manifold gasket, get real. I replaced it with a metal one. GM had a new one created for this fix made still out of plastic with two metal studs how stupid can you be I want my future cars to last forever period

- laughing hyeana, Auburn Hills, Mich., US

problem #5

Oct 302007

(reported on)


  • Automatic transmission
  • 66,000 miles

My Husband notice that the temp in the van was running higher then normal and then dropping after we took off. I called a garage who said it could be the thermostat. When I went to get my oil change I told them what it was doing and when they check the could see the Coolant leaking, we were lucky because it had not yet mixed with the oil. They would not change the oil and quoted me 800 to fix. I called the dealer, whom which I had already paid for all my sch mtce and oil changes, to advise of the problem, they would not help me out. I just pd them not 6 mnths before for there 60000 service and was told they had a bulletin on this and were supposed to check it, if it was bad they were supposed to replace.

Took it to my garage and found out that I also needed a new master cylinder, per my mechanic that was the 3 gm that week with the sam problem. We caught ours in time and there was no water in the oil. They replace the DexCool with regular AntiFreeze, because Dexcool in known for eating away at plastic. Well know we are at 99000 miles and guess what car is running high then low again and heater does not work!!!!!

- K S., Calera, AL, US

problem #4

Jun 132007

(reported on)

Montana EXT 3.4L

  • Automatic transmission
  • 50,000 miles

gm has never corrected this issue, started in the mid 90's,

i think they have a service note on this issue. (what about a recall) FIX THE PROBLEM GM, YOU ARE LOOSING CUSTOMERS BY THE TRUCK LOAD................ THEY ARE DRIVING TUNDRAS<>

20,000 should buy you more than 50,000 miles before major repairs.

PS. Transmission acting a little funny as well.



- mcgaffick, Salem, OH, US

problem #3

Mar 142007

(reported on)

Montana 3.4L V6

  • Automatic transmission
  • 97,000 miles


Approximately four weeks, ago we had no heat in the car. We stopped at the local mechanic and he checked the coolant level. Indicated that this was a problem with the GM engine intake manifold of this design. He put coolant in the car to get us where we were going, but said it will need to be fixed. We drove limited,(within two days we did not drive it at all and have not driven it since.) We contacted the Gm Service help line, and got the run around, they say the problem is the engine has miles on it and it is old. From the research we have done this is not a engine wear issue. With no warning we started the car and it blew oil near the filter area. The oil on the garage floor appeared to be free of water. My husband was trying to find a leak put a new filter and oil in the car. Same thing happened. At this time we had the car towed to the dealer. The dealer indicates there was water in the oil and they think we spun the crank and plugged the oil holes causing the pump to blow oil out the filter.

Again there was not advance warning there was a possible problem with the car. At this point the engine has not been torn down, they recommend engine replacement....$5000? But... Gm says there is not a problem.....

There is another car in the family, the exact same year, make and model with the same coolant leak problem, less miles.

- Tammy G., Madison, OH, US

problem #2

Nov 182006

(reported on)

Montana 3.4L V6

  • Automatic transmission
  • 49,000 miles

Coolant in the overflow reservoir continuously disappears. Engine continues to overheat. It will start with a normal reading on the temperature gauge as soon as the engine has warmed up properly. Thereafter, the temperature fluctuates up and down, and overheat mostly at an idle position. This leads me to believe that the thermostat might be sticking. Visiting my local mechanic enlightened me on the problem. He informed me that this has become a continuous problem with the 3.4L V6 engine in Pontiac Montanas'. He says it has been commonplace to have to replace the head gasket because the original one tends to disintegrate over time. Water seeps into the oil in the engine. The longer one waits to correct the problem, the worse the situation might get. To replace the gasket, he quotes me a cost of $600.00. He warns me that if we wait too long, the water will warp the engine and then an engine replacement will be necessary. Does anyone know of a recall? I searched online, but could not find any recalls having to do with this problem.

- Emilio C., San Antonio, TX, US

problem #1

Mar 302006

(reported on)

Montana EX

  • 74,000 miles

I own a 2003 Pontiac Montana. It now has 74,000 miles on it. SURPRISE!! Out of the blue, it did not overheat, and was not running bad, but it has a huge amount of water in the oil. Funny that the standard warranty has long expired. Our local mechanic was baffled. There is no water in the cylinders, but the oil pan is full of water. Our mechanic replaced the intake gaskets, but it is still sucking water into the oil. He is now in the process of ripping it all apart AGAIN to replace the head gaskets. I am shocked that the quality of GM cars seems to have declined since the early 70s. They used to last about 100,000 miles before they fell apart. I am extremely disappointed. It's no wonder that the recent imports are kicking GMs butt. It comes down to quality, reliability, aggravation, and repair costs. I will be selling/trading my Montana as soon as it is fixed. This type of problem started with the 1999 GM minivans. Unfortunately, I was unaware of it before I purchased my 2003 Pontiac Montana. I wonder why after 5 years, GM still can't seem to correct their obvious design flaws.

- kstumpf, Ozark, AL, US

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