: 1990 Brougham 307 V8: Weird engine noise



MadCaddie69
04-23-09, 11:16 AM
So yesterday, I tried to clean my carb with Gumout Carb and Choke cleaner. I sprayed the secondaries. Now my car's acting up. The Oil Pressure light flickers and the carburetor is out of tune. On top of that, the engine is making weird rattling sounds like the catalytic converter is bad or something. Any clues or what's going on?

cadillac_al
04-23-09, 02:44 PM
It sounds like it is just idling too low now. My theory is the secondaries may have been sticking open a little bit and now they are not, so you may have to turn up the idle adjustment.

MadCaddie69
04-23-09, 03:20 PM
It sounds like it is just idling too low now. My theory is the secondaries may have been sticking open a little bit and now they are not, so you may have to turn up the idle adjustment.

That's what it may be. But what could be causing the rattling noise?

sven914
04-23-09, 06:22 PM
The Stop Engine Oil Pressure indicator goes out when the minimum oil pressure has been met for engine operation. The light coming on indicates that not enough oil pressure is being built up (the pressure could be just high enough to turn off the light), which means that some things in the engine may not be getting lubricated. The rattling you are hearing could be the valves clicking from lack of oil.

Or if the engine is shacking the car, then any thing that is loose on the engine, chassis, or body could be rattling.

MadCaddie69
04-23-09, 07:56 PM
The Stop Engine Oil Pressure indicator goes out when the minimum oil pressure has been met for engine operation. The light coming on indicates that not enough oil pressure is being built up (the pressure could be just high enough to turn off the light), which means that some things in the engine may not be getting lubricated. The rattling you are hearing could be the valves clicking from lack of oil.

Or if the engine is shacking the car, then any thing that is loose on the engine, chassis, or body could be rattling.

Makes sense. If it's the valves, what should I do?

jayoldschool
04-23-09, 08:04 PM
What's the mileage on the car? My 307 that was in my 87 Caprice started to do the same thing once it had lots of miles. The oil light would flicker when the engine was warm, in drive. It would go out once the pressure rose with RPM. I also think your rattling is the lifters/rockers experiencing a lack of oil pressure. The cause is either the oil pump getting weak, or clearances opening up in the engine due to wear. I'll bet on the first one. To change the pump, the pan has to come off.

For now, raise the viscosity of oil. Go with a 5W40 or 10W40 and let us know if it makes a difference.

MadCaddie69
04-23-09, 09:23 PM
What's the mileage on the car? My 307 that was in my 87 Caprice started to do the same thing once it had lots of miles. The oil light would flicker when the engine was warm, in drive. It would go out once the pressure rose with RPM. I also think your rattling is the lifters/rockers experiencing a lack of oil pressure. The cause is either the oil pump getting weak, or clearances opening up in the engine due to wear. I'll bet on the first one. To change the pump, the pan has to come off.

For now, raise the viscosity of oil. Go with a 5W40 or 10W40 and let us know if it makes a difference.

My car has 183K miles. It was running fine until I sprayed the carburetor with carb and choke cleaner. After that, that's when the noise started. I was just researching about lifters. That must be it because it sounds like it's coming from the heads. What's your theory on that?

jayoldschool
04-24-09, 02:02 PM
I bet it started after you sprayed down the carb because the linkage is now free to move through its entire travel. Therefore, it idles lower than before, and the pressure drops.

That's lots of miles on a 307. Time for thicker oil (at least).

MadCaddie69
04-24-09, 03:47 PM
I bet it started after you sprayed down the carb because the linkage is now free to move through its entire travel. Therefore, it idles lower than before, and the pressure drops.

That's lots of miles on a 307. Time for thicker oil (at least).

Yeah, it's a lot. I put two bottles of STP Oil Treatment in it. I tried to drive it around the block and it's more sluggish than before. I'm not tryin to lock it up. And I just renewed the registration last week!!

akimball442
04-24-09, 08:04 PM
You might have caused a massive vacuum leak, too. A small leak might increase the engine speed some. A large one would cause it to run terrible.

True story- Last year I was working on an 87 olds wagon with a 307. 240K miles. It ran fair. Caked on with grease and grime

Cleaning the top of the engine caused it to run terrible.

Half the grease was plugging up air leaks. I ended up overhauling the carburetor and replacing all the vacuum lines. It ran marginally better.

The big improvement was replacing the EGR valve. It was partially stuck open. Check for that, too. That will cause an engine to run bad, basically because it's a massive air leak.

cadillac_al
04-25-09, 08:39 AM
I always unplug the EGR on 307's and I'm a believer in 15-40 oil when engines are old and loose. I would still turn the idle speed up a little just to keep the oil pumping.