Coolant Leak

BrianBronc · April 5, 2005

I have a '98 GMC Sierra.

It is leaking at the back of the engine down the bellhousing. It it definitely coolant. It is not coming from the overflow bottle and can't feel any leakage on the heater hoses. I have read on here that it could be the Intake gaskets or the rear freeze plugs.

How can I check and verify which one? I can;t really see the back of the engine no matter how I look. If it is the intake gasket, is that somehting I can fix or should I have someone work on it. I turn a wrench pretty good, but no newer engine experience. Is there some info out there on this replacement?

thanks

brian

TexasAggie · April 6, 2005

Brian,

I am assuming that you have the 350 Vortec in your GMC and given the year and the description you have given, I would bet that the right rear intake gasket has crumpled around the rear water jacket. If you get yourself a telecoping inspection mirror (any parts store) you can take a peek at the back side of the head and you will be able to see where the coolant is coming from. Most likely you will be able to see the coolant coming out. Start with the engine cold and get your mirror and a light ready and start the truck...then watch the back of the head/intake interface. The leak should be visible.

Personally, it isn't that complicated to replace, very much the same as any other intake gasket if you have experience with chevy small blocks. The only real difference is the upper plenum on the vortecs, but you will get a new seal for that in the kit, so no worries. However, be very careful with the injector tubes and retainers, they will be brittle. If you need some tightening sequences or other details, let me know, but I think that anyone with some prior small block knowledge can do the repair. Other than that, it is old school, flush and refill coolant and I would also suggest an oil change too. Some on this forum swear against the DexCool, but if properly maintained and mixed with distilled water when refilled, you shouldn't have any problems...

Yell back with what you find...

carl722 · April 7, 2005

I replaced mine but I didn't seperate the upper plenum from the lower part there is no need for that. Mine was leaking in the front right side internally to the intake port and the quick connect coupling for the heater hose was also leaking. You are suppose to torque the intake 3 times the last time being like 9 or 11 ft/lbs. I don't remember the sequence but if you have a Chilton's or Haynes manual it will give you the sequence and the torque specs.