Hello,

I'm helping my father with his 1999 Monte carlo V6 3100 engine (I think that's it).. 105k miles.

He went to have the radiator flushed and the service station told him there was oil in the water...

He thinks it may be his radiator, I think he is dreaming. I believe it is the head gaskets.

Is there a common known issue with this engine? How difficult is head gasket replacement? Does the head gasket job require pulling the engine? Is it worth replacing the gaskets or is the engine toast? He's retired and on a fixed income... Any suggestions are welcome.

redbug,

There is no "path" for oil to the cooling system through the heads on the 3.1. The ONLY way oil can get into the cooling system is by a "pressure leak". That is, somewhere in the block, an oil passage is cracked or broken adjacent to the water jacket. There is no oil PRESSURE in the heads. Only "splash", which cannot override water pressure.


We've seen transmission fluid in the radiator often, caused by a failed "cooler" that runs through the radiator. Unless there's an oil cooler in there as well, it's either trans fluid or a cracked block.

Jim

What MrPbody said is exctly right. I would check the transmission fluid level just to make sure the cooler isn't leaking into the radiator. Also if you haven't flushed the anti-freeze before afyer 10 years, it can turn black and appear oily.

Probably the intake, there bad about leaking an it will allow oil to get into the cooling system.I've done two, one 3.1 on a 95 monte and a 3.4 on a '01 monte. One sign is you might see antifreeze residue under the throttle body, on top of the transaxle area. One Gm fix is their stop leak but if the gasket has to be replaced, auto parts store offer a plain jane gasket set and "the fix" style that cost quite a few more dollars. These are plastic gaskets that just get tired after thousands of miles and heat cycles

Probably the intake, there bad about leaking an it will allow oil to get into the cooling system.I've done two, one 3.1 on a 95 monte and a 3.4 on a '01 monte. One sign is you might see antifreeze residue under the throttle body, on top of the transaxle area. One Gm fix is their stop leak but if the gasket has to be replaced, auto parts store offer a plain jane gasket set and "the fix" style that cost quite a few more dollars. These are plastic gaskets that just get tired after thousands of miles and heat cycles

Agreed... Go with the metal intake gaskets (around $95 / set).. I've done it on a '97 Blazer, '99 Grand Am GT and '98 Monte Carlo.. On the 3.8 also watch for the upper intake plenum having a burn hole where the EGR pipe goes through it.

The "oil" could be DexCool sludge instead of oil...

.... the voice of experience talking....

if theres oil residue in your radiator u need to do a lower intake gasket change. I done have many replacements on these cars they are bad about leaking. I had to do two last week.