I have a 2005 Buick Century 3100 SFI and it is leaking coolant from the top driver side Engine Mount. It looks like it is coming from the bottom most bolt (there are 3), that holds the mount to the block. I can see the coolant between the mount and the block. It runs down the front of the engine from the mount. This seems to be below the lower gasket which is dry. Is there a freeze plug in between there? Could it be leaking out of the bolt holes? I thought it was the intake manifold gasket and just got a great quote on fixing it, but after another look and some research it seems to be leaking from below the lower gasket for the intake. Engine starts and runs great with no loss of power. Any feed back would be greatly appreciated!!!!!

Sometimes it is difficult to pinpoint the real location.
Get engine all clean with a quick power wash, and use a rad pressure tester.
Pumping it up to 16 psi may help to find the exact leak area better.

It is in between the motor mount and the engine block. I can top off water and start the engine to reproduce the problem. Looks like out of the mount bolt from the side of the block. Is there a freeze plug there? I can't getter a better look without removing the engine mount itself. Could it be leaking from the actual bolt some how.


It'* coming out where the bottom mount bolt is seen going into the block or right above it, but behind the mount plate. Here are some more angles...

Here it won't let me edit the first reply...

Sure it'* not the lower intake? Possible head gasket?

When not sure of the origin, I like to use a coolant dye and black light to follow the trace of the fluid....

Watch in HD

Yes, there is a freeze plug behind that motor mount bracket. To fix this problem, you will need to remove the air intake tube then remove the throttle body then remove the thermostat housing then remove the motor mount bracket then remove the freeze plug.

I just did this job last week. Anybody can do it with a few simple wrenches and a screwdriver. I installed a steel freeze plug......I think it cost all of 25 cents wholesale bulk......auto parts store probably sells the same plug for a buck. Brass freeze plugs are an option, but I would advise against it. Adding brass to the aluminum cylinder head is not good for the engine as it could promote electrolysis corrosion between the different metals. Brass and iron is ok, but brass and aluminum is a no-no.

A lot of work for a simple "freeze" plug. Actually that is a misnomer, the plug is actually a casting clean out plug but somewhere along the line someone thought they were freeze plugs and started calling them such. If you have to take the throttle body off might as well remove the sensors and give it a good cleaning. Since you have to take the thermostat housing off, you might as well get a new thermostat and gasket and replace it for preventive maintenance.

Yes your correct the holes are there to get the sand out after casting them so a lot call them core plugs.
The freeze plug name came after some got lucky with water only in the block and when the water froze solid they popped out the core plugs saving the block at times.
So a lot of people got the idea they were made to do that by the manufacturer

One of the mount bolts is well behind the exhaust shroud. How would I go about removing this bolt?