Hey all, thanks for taking the time to read this. I’m a new Blazer owner and love it! Got a 98’ Blazer 4.7L 4-door automatic, 127k mi. and running strong. Today while in stop-and-go traffic, I started seeing steam rising past my driver’s door, a little on the windshield, sometimes from the front of the truck. I pulled into a gas station ASAP, looked under the truck and I saw the green coolant dripping over the automatic transmission just behind the engine. I opened the hood and checked all the coolant lines I could see using a flashlight and no spraying or steam! Hmmmm. I even looked at the lines going through the firewall to the heater core and they were fine. Now, I do have a developing greasy film on the inside of the windshield and this would indicate the heater core has ruptured right? I read here somewhere that a guy poked a minor hole in the bottom of the box to see if any coolant drains, if so, then replace the core. Is that my next step? Or are there any hoses in the back of the engine I need to get back there and check first? I’m pretty handy with auto repairs up to a head gasket replacement, but I wanted to check with you all first before diving into this machine.

Thanks!
George

 

Check to see if you passenger floor carpet is wet, if it is probly heater core.

 

Isn't the heater core sealed in a plastic housing to prevent scalding coolant from spraying the passenger/drivers legs? I'll check, but I have weathertech floor mats that cover the entire floor area and I would have seen right away if there was any liquid on them. But I will pull them and check after I drive home from the office tonight.

 

No coolant on the floor and it's still leaking from the same place under the car. Does anyone know if you can see the drain hole for the heater core box from underneith?

 

I may be sealed but it does still get the pass. floor wet if it leaks (usaully). It seaps out so most of the time you never notice it leaking except the wet carpet and the nasty smell (some say sweet smell).

If you cant find it what i do is go to advance auto they rent a tool that puts pressure on the system. Pump it up and with out the engine running you can hear the leak. I have never tried this on a blazer. It has worked for me on many other models of cars.
http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_Radiator-Pressure-Tester-Stant-BP_16090002-P_N3388_T|GRP2018____
This is like the one they rent except the rental has lots of adapters.

 

I'm guessing you have an intake gasket leaking

 

Freeze Plugs....

 

There are no freeze plugs on the back of the engine.

 

Take a light and an inspection mirror and look at the top rear of the engine. I suspect you will find the leak from the lower intake manifold gasket.

 

I had the same problem with the 2002 ZR2 I just bought. It ended up being the intake manifold gasket. I was getting ready to replace it when I thought I'd check the torque on the manifold first. The thing was barely finger tight. I retightened all the manifold bolts to 13 ft lbs per the manual and it hasn't leaked a drop since.