Hey guys, I have been reading up on all the overheating/head gasket leak/LIM leak threads and still haven't really been able to find the solution to my problem.

I live in central TX and the heat normally stays in the 90s everyday, and for the past couple of months I have noticed that I have been losing water, and my temperature have been rising at idle. 2001 4x4 LT with 150xxx on the clock.

Things replaced and checked recently.
-New thermostat after old one stuck closed
-New radiator and hoses
-New fan clutch
-Transmission rebuild (not sure if relevant)
-No smoke or water coming out of exhaust, minus normal startup drips
-No water in oil
-Have been placing cardboard under blazer overnight to see spotting, yet nothing is showing up
-Still have heat and A/C, no soggy carpet

So here I am confused as hell still. Scenario normally runs like this. I refill the radiator with water, it drives fine for a day or 2, except it never really hits operating temp. Then as I'm in slow moving traffic or just at idle, the temperature will start to shoot up to around 235 i guess, not ever really going further. If I am moving faster than 45 mph, airflow will always bring the temperature back down to the 190 mark. If I turn the heater on the temperature will shoot back down of course, but its already hot as hell outside and I'm not using the A/C at all because I don't want to add any more heat to the system at this point. The one thing that is messed up right now is my lower fan shroud has been broken for some time, yet I didn't believe it would drastically effect the temperature like this.

Most of my driving is highway driving so its not too bad, yet I just hate always having to watch the temperature gauge and also when I turn the engine off it will jump to about 235 until it airs down. Any insight?

 

well i got a scenario, 1 of 2 things... pressure and/or mixture. are you running 50/50 water coolant? i have in my theory that youve been adding water. water cools better but the coolant stabilizes water to raise its boiling point. so u fill it, water boils, makes air in system, restricts flow, steams off in overflow, system gets low , gets hotter, worse and so on. adding strait coolant concentrate will run hot also but not boil. now the pressure. the system is pressurized to remove air, promote circulation and water has a HIGHER boiling point the higher the pressure is on it. so i want you to remove the radiator cap, out 2 thumbs on it and make sure the spring is stiff and smooth and extends the inner seal to its peened over stop. if weak or broken spring it will not generate pressure needed. also that shroud as simple as is seems may be all of it too, fan can not pull good vacume on radiator when sitting still if its missing or not fitted tightly. if its not leaking at all, a slow intake or head gasket leak, crack wont always show easy.... 1 more thing is back to circulation, its rare but ive seen water pump impellars wear right off flat and not move fluid well of course worse at idle. so with all this said (sorry about the rant) whats going on in your situation? let us know

 

That's a lot of good info Tom. I've had my lower shroud missing for a couple of years and it, in itself, shouldn't cause a problem. The weather here in Florida is similar to Texas except we get more rain. What's weird in this case is that it's not getting up to temp which, to my knowledge, is only caused by a thermostat stuck open or winter temps in the northern tundra in which Texas is not geographically located.

I can verify that it is possible for the lower intake gasket to leak and not be detected. If there's a small leak on the inner gasket leading into the engine valley the coolant will instantly turn to steam when it hits the block and not drip into the oil. Mine was like that for a year until it decided to catastrophically blow out at which time there was no debating the diagnosis.

 

Duuuuuuuuuuude you may have solved the problem. I have been using just water, since I didn't feel like buying coolant repeatedly just for it to disappear. Maybe the water was boiling off and creating air pockets in the system? Maybe this is why my temperature has been sticking around 160 and killing my gas mileage.

I guess that I should have stated, when I changed the fan clutch, it was about a day before the original post, and I had forgotten to refill the radiator after. Today, after work, I switched rides into the blazer and started on a journey to figure out the problem. The radiator cap was fine, and I topped off the radiator and reservoir and got on the road. To speed up the process I turned on MAX AC and put the blower on 4 for the WHOLE TIME DRIVING.

-10 minutes of highway driving into town
-30 minutes of either 45 mph or lower, or sitting at idle or in park while eating sonic and looking for active leaks
-10 minutes of highway driving back home.

It took 25 minutes of the truck sitting at about 160 before it finally started to creep towards the 210 mark. When it got close, I pulled over and sat at idle for a couple of minutes to see whether the temperature would hold, and it did with no problem, this is with max ac on full blast mind you. When I went to head home though, the temperature dropped back down to the 160 mark and stayed there the whole rest of the way. So tomorrow I will drain the water and go back with coolant/water mixture and try to burp the system and see if anything changes. Also, I run a CAI, but I doubt that has anything to do with a temperature difference of this size.

Long post sorry

 

Truck Tom thumbs up !!! I was thinking the same things as you!!! I figured radiator cap was getting old !!! Every 1psi of pressure in the system raises the boiling point 1 degree ,,,thats the rule of thumb

 

Actually a little over 2

 

wow thats great info thanks