Ok, my sisters got a 98 Chevy Blazer 2wd Auto with a 4.3 Vortec in it. Coolant is mysteriously disapearing. About half a gallon every two weeks or so. There are absolutly no external leaks. Radiator cap is good. Pressure tested the system. Didn't loose any pressure in 3 hours I left it on there. The thing has absolutaly no overheating problems, and seems to run great. No steam out of the exhaust or anything. Any ideas? I'm stumped on this one.

Coolant leaks at the intake manifold gasket are common on these engines

Most of the intake gasket problems were pretty well wrapped up by 1998, but I wouldn't rule that out.

 

Is it all lost in the radiator, or is the overflow tank draining as well? If the radiator is just a bit low; that is completely normal. Most all of these I've ever had would "shed" coolant if you filled the radiator to completely brimming full. I'd recomend filling the overflow tank to "full cold" while the motor is cold, and then fill the radiator to near the top, but not full. If you can stick your little finger in, and touch the coolant; that is full enough.

 

Another place to check for small leaks is under the passenger side carpet. If the heater core is starting to go (common on these) it can leak very slightly, be absorbed by the carpet, and then evaporate without you ever noticing.

 

Also be sure to check the wheep hole on the water pump. It is common for those to leak so slightly it isn't noticeable, and the coolant evaporates from the heat of the motor. You have to get underneath, and specifically check for marks right around the wheep hole.

 

GOOD LUCK!

Coolant leaks at the intake manifold gasket are common on these engines

 

 

Gaskets were replaced 4,000 miles ago. Could it maybe be the trans cooler leaking?

The trans cooler lines should run into the side of the radiator. They do leak, but that would be fairly obvious. You can tighten both the hard cooling lines into the radiator bungs, and the bung into the radiator. The bung does leak from time to time, and can be tightened with a large crescent wrench. Do so slowly, and carefully. Overtightening can crack the radiator tank. That would make for a much larger, more noticeable leak. :-\

Hrmmmm

 

You may need to clean the engine, radiator and frame, then put a dye that responds to balck light in the cooling system. Its possible you have a hairline crack in the radiator that only opens up when hot.

 

 

nipper

I still say intake gaskets and maybe even head gaskets. The Vortecs were notorious for this, mostly because of that crappy extended life orange coolant they used.

I had an intake gasket on my chevy leak once but you could see it spewing onto the ground.

The intake gaskets have been done around 4,000 miles ago. I really hope thats not the problem again. Put the pressure tester on it again today, needle doesn't budge. Started the truck up with the tester hooked up. Needle doesn't move Pulled the carpet back to see if the heater core might have a very small leak. Everything is dry. Everything seems to be in check.

 

I gave my sister a couple of gallons of deathcool and showed her how to check the rad, and told her that she needs to check the coolant level every few of days.

 

Will it hurt anything to run regular antifreeze in this thing as long as I compleatly fluch out every bit of this red crap? I don't see what it would hurt. I know if you mix the two it isn't good, but I hate to pay a little more for the deathcool, just to have it sludge up 6 months later.

No, as long as all the red crap is outta there, it would be better to run green stuff!!

yes flush it out good and add the dye. the dye works very well, we used it in the the gm dealership alot. i've seen the dexcool completly clog a cooling system. you should be able to get the dye kit at any parts store.

I bought the whole 100 dollar kit able to test all the fluids to sometimes help assess HG issues on the 2.5 SOHC's. It'll do oil, tranny, coolant, and AC. Comes in a nice case with the spiffy glasses, IIR a flashlight and a 110 light.

 

Was a quality new intake gasket used? Most guys have replacing these 4.3 intake down to a science like the 3100's.

 

In my dad's I put in the Advance universal stuff that looks like Mountain Dew. BTW dad's truck is a 98 GMC Sonoma.

 

My local rad shop says to NOT use the original stuff, and that there are many issues and law suits about it.

Yes the original stuff has caused many many issues and lots of lawsuits.

 

 

 

nipper

Yes the original stuff has caused many many issues and lots of lawsuits.

 

 

 

nipper

 

 

Most of them being related to people not reading their owners manual, and mixing it with non-extended life. We had a little science expiriment, and mixed the two. That's definitely the source of most of the clogs. People "top up" with a little of whatever they have, and it makes a nice pudding.

Most of them being related to people not reading their owners manual, and mixing it with non-extended life. We had a little science expiriment, and mixed the two. That's definitely the source of most of the clogs. People "top up" with a little of whatever they have, and it makes a nice pudding.

 

I sometimes think that everyone should be required to have a mandatory 1 hr course on thier cars when they buy them.

 

Also I have seen it where the MFG doesnt really mark it well under the hood that any fluid is special, except for maybe tranny fluid. Now new soobies have a long life coolant that shouldnt be mixed either. Engine oils (for the DYI'er with a little knowledge and a lot of tools) are starting to get specific (motorcycle vs industrial vs classic engines).

 

Going to be another long learning curve.

 

nipper