View Full Version : Need some help with the 307.

01-01-10, 05:11 PM
Hey guys,

I can usually figure out a problem or search threads here for answers, but I am stumped on what's giving me the trouble I have with my Olds 307.

It's actually not in a Cadillac, but I figure people here are so GM savvy, this would be the best place to check. It's the stock motor in my '83 Oldsmobile Custom Cruiser 9-vin.

The problem: Continual smoke from the engine bay. And here's the timeline leading up to these continual problems with the motor.

1. Couple months ago my water pump gave, engine had overheated, but I killed the motor quickly. I replaced the pump and my stuck-open thermostat. The car had been running cool and I replaced it, so I would reach optimal temperature and fuel economy. My old water leak is now fixed. :D

2. Engine begins to smoke, smells of burning grease and oil. I thought since I replaced the thermostat, the smoke was from years of caked engine grease now burning as the engine became warm. My solution: remove the thermostat. I did.

3. Engine continues to smoke. Though not overheat and doesn't smoke as much. There's no oil in the water or water in the oil. I added some Bardahl's to the oil just to be sure.

4. I check the tranny fluid. Oh no! I'm bone dry, I add some and the smoke goes away! Car is fine - for a day. I find I have a major tranny fluid leak. I add some Bar's tranny stop-leak and it slows the leak. Though I still have to add a pint regularly, but the engine continues to smoke as though there is no fluid.

The car has always shifted and runs fine, and never overheats. Now with the fluids topped off, there's still smoke from the engine bay. It comes from the back of the motor near the bottom and is a burning type of smoke. It stinks and it will suffocate you if you drive with the windows closed. :eek: And when the engine is running, the smoke seems to "pulse" with the speed of the motor - maybe that's just the fan but weird no less. The smoke continues to bellow out for a couple minutes after you kill the motor.

It appears to come from some oil dripping on the exhaust manifold, but it just seems like too much. And the smoke doesn't really smell like oil.

Any ideas?

01-01-10, 05:28 PM
read your poat. Losing Tranny fluid, smoke, might be related. Where is the fluid leaking from the tranny? Rear seal, pan, pump housing, converter seal? Have you looked underneath with the car on a hoist? How soon after start up with a cold engine does it take before the smoke starts?

01-01-10, 05:31 PM
I have been meaning to see where the fluid leaks from, but since I put in the leak-stop it's been hard to spot. I'll continue to check.

It's smokes shortly after startup, within 2-3 minutes.

01-01-10, 05:39 PM
It's smokes shortly after startup, within 2-3 minutes.

That's about how long it takes the pipes to get hot enough to burn oil. there is a posiblity engine oil is buring off the manifolds, but you said it did't smell like oil

01-01-10, 05:51 PM
I suppose it could be oil. But it's such a thick smoke, and it smells very burnt. I've been around old cars that smoke and "burn oil" and it doesn't smell quite the same. I suspect it's tranny fluid coming from somewhere.

01-01-10, 06:57 PM
Got a pic. Ever since my automatic choke duct tore off, it seems much of the smoke has been coming from the opening.


I also noticed there is some fluid on the exhaust pipe, right under the back of the motor where transmission hooks up. I have always noticed fluid hanging around back there on top of the tranny. It seems to be leaking large amounts from back there and dripping out on the exhaust.

How do I stop such a great leak? The Bar's leak-stop at least stopped it from completely dumping on the ground. It actually doesn't drip anymore.

EDIT: Don't think it matters, but I noticed my flywheel housing is busted and cracked a bit.

01-01-10, 08:32 PM
That hole for the heat riser does not go directly into the exhaust stream. If you see smoke coming from it, then there might by a hole in your exhaust manifold.

Another thing that can cause smoke is antifreeze. Burning antifreeze has a very distinctive smell and does not spell like burning oil. It will give off a white smoke.

Your transmission leak could be in the torque converter. The torque converter is in the flywheel housing. Fluid in a cracked housing can easily be sprayed onto the exhaust cross over pipe.

01-01-10, 08:56 PM
Looks like a decent oil leak from the valve covers. Another thing may be the rear of the intake leaking antifreeze, mine did after the engine got hot.

01-01-10, 09:10 PM
No it's not antifreeze, I am familiar with that sweet smell. But my flywheel housing is torn enough that I can see the flywheel when I kneel down to have a look below.

I did notice my tranny pan is fairly wet with fluid. It looks like the fluid trickled on to it. I used to think I had a pan gasket leak but thought I'd stopped it. How do you resolve a torque converter leak?

01-01-10, 09:34 PM
Then its probably the oil smoking. It may smell a little off because of the bardahls additive. A convertor leak repair would require the tranny to be dropped.

01-01-10, 09:50 PM
Is a rear main seal leak a possibility?

01-01-10, 10:09 PM
Yes... But that would smell like engine oil, and if you are losing that much oil to make that much smoke, then you would be toping off the crankcase. Hope for a converter leak because the only way to fix a rear main seal is to lift the engine.

01-02-10, 01:04 AM
I suppose I need to isolate the source. I'm doubtful it's the rear main seal because I'm not losing much oil. And I have lost a great deal of tranny fluid only. I could probably live with the leak (it's not the greatest car in the world) if I could just stop the burning.

01-02-10, 01:10 AM
read your poat. Losing Tranny fluid, smoke, might be related. Where is the fluid leaking from the tranny? Rear seal, pan, pump housing, converter seal? Have you looked underneath with the car on a hoist? How soon after start up with a cold engine does it take before the smoke starts?

I meant the rear seal on the tranny

One thing that can cause all sorts of funny smells is a defective Positive crankcase ventilation system. Missing broken or clogged parts can lead to a pile of smoke and smaell on high mileage engines