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My 94 Bonneville SLE (~84K miles) was slowly leaking coolant for about a month. I could see coolant on top of the engine between the valve cover and I believe the lower intake manifold; a small spot was also evident on the ground below the engine. I was adding about 8 ounces of coolant every 2 weeks to keep the overflow container full, and there was no evidence of coolant in the oil.

Then late one evening I noticed a very large spot of coolant on the garage floor & that the overflow container was almost empty. I haven't started the engine since.

Does it seem likely that the same bad part would cause both the slow and rapid leak? What areas would you recommend I scrutinize? Lower intake manifold gasket, throttle body gasket, coolant bypass hose, water pump, etc? Which part(s) typical go bad on this vehicle? Thanks, in advance.

if it leaks that fast, I would fill up the overflow and get under the car and watch for the trail of coolant/water - once you get the trail, you follow it to the top of engine and narrow it to offending parts

Are you able to post pictures of where the coolant is pooling please. There are several possible offenders in the areas you could be describing.

RJolly87 wrote:Are you able to post pictures of where the coolant is pooling please. There are several possible offenders in the areas you could be describing.

RJolly, thanks for the reply. I have a picture to post, but I need help inserting it. Can someone please provide directions? (I read the FAQ.)

Additional info on the coolant leak: Today, I removed the radiator cap to check the coolant level. It's only about 5/8 inches below the radiator filler neck. However, shortly thereafter, with the radiator cap still removed, coolant started dripping onto the garage floor.

I could not detect any coolant leaking from the top of the engine. However, I can continually collect coolant on my finger if I put it underneath the water pump area.

Thanks again for your help.

You're going to have to follow the stream of coolant to track it to the source, because many things can affect that area, including the water pump itself (there is a weephole at the bottom of the pump shaft), coolant bypass, heater hose inlet, and lower radiator hose fitting.

RJolly87 wrote:You're going to have to follow the stream of coolant to track it to the source, because many things can affect that area, including the water pump itself (there is a weephole at the bottom of the pump shaft), coolant bypass, heater hose inlet, and lower radiator hose fitting.

RJolly, thanks again for the reply. I didn't see any stream of coolant from the coolant bypass hose, heater hose inlet, or lower radiator hose fitting. Unfortunately, I'm not able to see the weephole area of the water pump.

The coolant pooling at the top of the engine was located between the rocker arm cover gasket and the lower intake manifold gasket under the three grouped spark plug wires on the dipstick side of the engine. (Could the source be a leaking upper intake manifold gasket?) I have a nice picture to show of the location if I can upload the image directly to the board (i.e., no URL).