Hi guys and gals. Ive got a problem. My 98 Blazer LS 4.3 liter 2 door 117,000 miles has been running pretty good for years. Yesterday after running some errands when i got home and shut it off i could smell coolant. Looked underneath and there was a steady stream of water coming out rear of the engine. after it cooled down i got underneath but couldnt find anything, checked the hoses and all that still nothing. Water in radiator was about 2" low so i added water and when i did water come running out at the rear of the engine. Still couldnt find anywhere it was coming from and of course you cant see between the engine and firewall. After the water stopped i checked the radiator again and it was about 2 inches low again so i filled it again and same thing happened. Today i didnt add any water and went to get gas and checked and no water leaking got home and shut it off and sure enough there was some water coming out. Then it stopped. Didnt add any water yet wanted to see if anyone had any ideas. Sorry so long but wanted to describe what was going on. Thanks for any help. Tom

 

It might be leaking from the back of the intake manifold gasket, where the manifold bolts to the head. You can't really see back there, but you can probably reach back there to feel (when the coolant isn't scalding hot). It could also be a leaking heater hose near the firewall or (you better hope not) bad freeze plugs.

Best thing to do is to pressure test it and look for the leak.

 

Thanks for the reply. i forgot to mention it idles okay and runs okay no hesitation or anything, water temp is normal. Went and picked up by grandaughter at school and when i got home i left it running and checked and when i turned it off it started dripping again. Will have to wait till it cools down to check it out. Thanks

 

The engine will run fine until it runs OUT of water and then overheats. At that point it's too late. The heater core is on the firewall in the passenger side. Just inside from the A/C condenser and drier. That's an easy place to look. If that's not it, yup, if it's the rear of the engine itself, freeze plugs. When you say you put water in, do you mean just straight water or the coolant?

 

Be sure to check the oil level to see if there is any coolant mixed in with it. This can occur if the lower intake manifold gaskets leak and allow coolant into the lifter valley. A leaky intake manifold gasket could also be the culprit if the leak is to the outside of the engine.

 

I have checked the oil and it is fine (just changed it couple months ago and it is clean). The thing is it seems to stop leaking when the water drops 2 to 3 inches in the radiator. It seems to be coming from the outside from what i could tell and it seems to be higher than the freeze plugs. Is it a job to change intake gaskets something i can do or take it to a garage which i cant afford $400 or more? Thanks for answering ....Tom

 

I have just been putting water in, it aint taking much. maybe 2 cups if that to top it off till it runs back out. I dont think it is a freeze plug cause it seems too high and like i said i dont lose much water....Thanks...Tom

 

In principle replacing the lower intake manifold (LIM) gaskets is straight forward. It is a hassle though. I did it over a weekend in my garage. The hassle is that so much has to be removed before you even get to the intake itself. In contrast, if I had to do the same job on my 68 Mustang with a 289, I could probably do it all in an afternoon.

The good news is that many of us have done this job and we can give you advice and share several threads and instructions on how to do it. We can also advise on the proper parts to get and other things you might as well consider addressing while you have it apart. For instance, I took the opportunity to change out the fuel injection system to the later version. You will also need a 1/4" drive torque wrench.

 

Thanks for the files, dang how do you remember where everything goes back. Looks like a mess. Am going to try this and see what happens. Again thanks....Tom

 

Take a lot of pictures with your phone as it comes apart

George