: 1990 Fleetwood Brougham, puzzling problem--head gasket?



EmperorOfIceCream
05-02-09, 10:17 PM
Hello all. I'm new here and I come to talk about Caddy's and seek advice for a problem with my 1990 Fleetwood Brougham.

Here's the details (I apologize for the long post but I want to make sure I'm thorough in explaining the situation):

She has a 307 Y motor, with just over 100,000 miles on it. Lately I've been noticing two issues cropping up.

The first is overheating as specific times. In normal driving, there's no problem, but anytime the engine is under hard labor for a length of time it begins to overheat. I first noticed this while pulling long, steep grades, like 2,000' ascent in four miles or so. The engine will show no problem during the climb. The coolant light won't illuminate, though the light itself works. Once I stop, however, after a few seconds, a rush of boiling coolant enters the radiator and overflows through the reservoir and boils out.

The second problem is a very slow trickle of oil and coolant, from somewhere near the back right corner of the block. It isn't frothy or mixed, but the fluids stay in separate drops and it's very slow. The oil needs to be topped off occasionally, but it causes no appreciable descent in the coolant levels in the radiator.

My concern is that the problem is a hole forming in the right side head gasket. However, there aren't too many other symptoms.

On one hand:

1. The engine runs smoothly, with no misfiring, though it pings slightly. I can drive the car all day in flat terrain and have no trouble.

2. The spark plugs are very clean, with no slime or carbon.

3. The compression is 140-150 psi in all cylinders.

4. There's no blue oil smoke nor coolant steam coming from the exhaust pipe.

5. The oil is black, with no sign of froth.


On the other:

1. The oil and coolant seem to be dripping from the same spot, near the block corner.

2. Back pressure seems to leak into the radiator. If I cold start the motor with the cap off, the water will begin to overflow after a minute or so.

I was wondering if it's possible for there to be a tiny, tiny hole in the head gasket causing the problem without making the engine seem overly sick?

I'm also probably gonna change the radiator, as the current one seems a bit gummed up, even after I flushed it. This might certainly contribute to the overheating, but I feel like there's something more complicated to it.

Thanks a bunch for any help that anyone can give me with this.

jayoldschool
05-03-09, 12:09 PM
That leak sounds like intake manifold to me...

EmperorOfIceCream
05-03-09, 12:20 PM
I was wondering about that, too. I've heard that 307's were prone to leaking intake manifolds.

My dilemma is whether or not to focus on the intake manifold first and risk wasting time and effort when the problem is the head gasket, or to risk going for the head gasket and unnecessarily ripping the engine apart.

I'm leaning more towards the first approach, right now.

jayoldschool
05-03-09, 02:08 PM
If the oil isn't milkshake, then it likely isn't head gasket. You can also test for by-products of combustion in the coolant.

EmperorOfIceCream
05-04-09, 09:17 PM
Thanks a bunch for the info. I'll look into a coolant testing kit to see if anything's leaking in. Best to narrow it down first.

cadillac_al
05-06-09, 09:37 AM
I don't think 307's are known for head gasket failures. I would start with the simple stuff. I would look very very closely for that coolant leak. It could just be a heater hose or heater valve. It wouldn't hurt to make sure all the intake bolts are tight. I would try a new thermostat just because they are cheap. It the T-stat didn't help then I would look into a new radiator. The oil leak is probably a valve cover gasket; they always seem to leak in the back.