have a 98 blazer 4 door lt 4x4 223,000 miles

One day got in and drove just fine next day got in and didn't have heat was looking over everything and noticed radiator was pretty low. I topped it off after adding about 3/4 of a gallon of antifreeze and went on my way and everything worked fine for about 2 days. It happened again so I started checking for leaks can't find any outside of motor and floor board is dry. Took and had a pressure test run and couldn't find anything. I keep topping it off and it keeps disappearing. I know that they are bad for intake gasket trouble but wouldn't that have shown on the test? People have told me headgasket but wouldn't it be smoking and running kinda rough? Also when up to cruising speeds (45+) while trying to maintain speed it's like it kinda jerks or sputters a little I'm thinking TPS or maybe fuel filter or something? Only does it when throttle is barely pressed to maintain speed of course not while idling or anything. Could prob figure it out myself just want a few other opinions. thanks in advance for the help gotta get this thing back on the road.

Ps radiator is full of what looks like stop leak and rust I know I should flush it and change thermostat and all but just seeing what else needs to be done so I can do it all in one go

 

Check your oil level, bet its in there, oil will be foamy
. If so, dont drive it any more, bad intake gasket most likely. Anti freeze will raise hell with bearings also. Change the gasket, drain the oil and puit new oil in it for a couple of hundred miles and change the oil again. Also say a few prayers. Good luck

 

Oil looks fine normal level and isn't foamy

 

this is a mystery

 

I too have anti freeze disappearing but I only lose about a quart every 1k. I also don't have any leaks, no Anti freeze in oil and no smoke to speak of. But I too notice it running alittle rough off idle until maybe 1600rpm but not bad. But at idle it is fine. I just added 1.5 qt of anti freeze and a 1/2qt of oil today.

Now you said you had it pressure tested did you test it when the engine was warm? And how long did you leave the pressure tester on it. That is on my list of things to do.

Well I myself think it might be the intake gasket.I was thinking maybe there is just alittle bit leaking into one intake port. I would think if it was either intake or head gasket with anti freeze going into a cylinder that it would smoke. So I am going to start checking the exhaust pipe. So if you find anything please let us know what you found and I'll be doing the same.

 

I didn't do the test myself to be honest so I'm really not sure and I agree on if it being a head gasket it would smoke so that makes me believe intake gaskets but in my opinion if I fix the intake gaskets might as well go through with changing head gaskets while it's all apart because id be pretty pissed if I changed intake gaskets and got it back together and it ends up being the head gaskets lol.

 

I would still consider focusing on the intake manifold gasket. That year is notorious for pin hole leaks

 

I myself find myself thinking that way too. I call it the snowball effect I always catch myself thinking well if I am going to repair this I might as well address this issue too. Even if it is a none issue. I blame it on my OCD !! More so on my truck since I like working on it. The Blazer isn't my fav as far as having to turn wrenches on. But the Blazer has to be RIGHT since my wife drives it all over God's green earth. She'll drive 200 mile away to spend the day with her family and then drive home the same day.

I have been doing some more reading on the intake leaks and I seen some guys saying they were having it leak on the exhaust to where it didn't leave a spot on the ground. So I need to get the engine cleaned too start with so hopefully I can find the leak. Right now the engine is so nasty it is hard to tell. Now I am getting some smoke when I start it up for about the first 20 minutes or 5 miles. But it hard to tell since it has cool and damp here. But as these guys have said these engines really don't have problems with head gaskets unless you overheat them.

 

Mine des the same thing, check between the intake plenum and the valve covers, that where mines leaking from i put a new radiator in (mine was pissing out anyways) and i rann it for a couple days and noticed my resivour was empty so i looked and looked and looked for leak then finally i saw a little shimmer and turns out it was getting burnt off before i could really find it but i did find it eventually

 

I am having the EXACT problem with the exact same Blazer, 98 4x4 4 door. The jerking and sputtering at cruising speed and all. Back in November my husband changed the intake gasket, and the overheating issue went away, until just yesterday, it started overheating again, coolant is low, can't find a leak anywhere. So either he didn't get it fixed right, or now the head gasket has gone out. I agree if you're gonna do the intake gasket yourself, might as well do the head gasket too, just to be sure you get it fixed and don't have to take it all apart again.