Hey guys. Drove the Jimmy today. So a few weeks ago I was having the temperature guage go between 210 and near redline all the time while driving. Changed thermostat, I finally had heat again and was running a solid tick below 210 without moving even under a 3,000lb load. All of a sudden today, no CEL but im running a solid 250F, also the truck seems to be making a pulsing rattle even tho I'm idling around 650rpm. Not to mention it keeps gobbling up coolant. Tank wont run fully dry but coolant level in the overflow tank gets low. Ive had this thermostat for about 3 weeks. Oh and also now I have no heat too. Just cool. Any ideas? I have 3 days to fix this before work again.

If needed I can record a video of me driving to show how quickly it climbs in heat but then stays directly on 250F.

 

​​​​​​Ehhhh. I sure hope that coolant is not going anywhere bad?

Any external leaks?
Any smoke ??

 

I havent been able to find any leaks. Very minimal smoke coming out of exhaust due to cold weather. Hoses are clamped tight.


Plus wouldnt I be overheating if it wasnt getting any coolant? Im not quite overheating, just running hot. Doesnt get any hotter or cooler. Just stays there specifically. And I know it isnt a bad guage. Used a obd2 scanner to see.

 

Ok, others will chime in, but I think the video would be helpful. You are "running hot;" I had a car that once did that, I forget the cause. You said you were losing coolant. I am concerned about your engine.

If you can do it safely and without damaging your engine, please post the video!

Might be localized overheating, might be not cooling effectively, water pump going out.. ?

 

I'm currently at work. When I get home I'll just pull out the gopro and just take a drivers video of the temp guage then I guess get out of the vehicle and show the tank and the underside for leaks.

 

Didnt even get home. It steadly increased in temperature the whole time. Never went down. But I stopped and pulled off, no leaks under the car even though the coolant tank has coolant. But I noticed the coolant level didnt raise when hot. Isnt the overfill tank coolant supposed to go up when the vehicle is warm?

 

Not sure what to think at this point...

Whats the symptoms of a head gasket or lower intake thingy?

Currently I have a little bit of smoke coming out of exhaust (70F outside) which the exhaust is also leaking some type of liquid. There is no visible leaks under the vehicle. The vehicle runs rough on idle. Its making random shivers every 2 seconds. Doesnt even try to cool down, it just steadily goes up to the redline now. Changed thermostat and did absolutely nothing. The oil doesnt appear to be "milky". There is a little bit of white speckling but nothing crazy. The oil stick still is brown.

 

When you checked the coolant hot, did the cap want to pop off as it usually does (was the system pressurized?)

If it is not pressurized, your water pump may not be circulating the coolant.

These engines are cast iron heads on cast iron block ? Same as my first VW so.. they can very likely take a bad overheat well. Yeah, they can still blow head gaskets and all that, but it has to be pretty severe (or driven until the engine stops running. BTDT) for that to happen.. then its Head Gasket vs New Head Gasket AND New Heads vs New Engine time.

Again, if your coolant was not pressurized. Then maybe it is just not circulating the coolant.. hence, low or no cooling system pressurization, making it not make the white smoke out the tailpipe
Or out any other leak
Or into the engine for milky oil.

 

Starting with the easiest.
Is there any debris, trash caught up in the grille? Any dirt still in the radiator from offroading or mud roads? Plastic, dead birds, whatever in front of the radiators?
Are the fan blades bent, damaged, the fan not turning? (Not sure if your's has an electric fan. If yes, key to OFF, can you turn the fan by hand or is it stuck?)

How do the fins of the radiator look? I've seen radiators blocked and not cooling because during winter somebody stuck a piece of cardboard down the front of the radiator and by pulling it out they had bent up a large area of the small fins obstructing air flow.

Switch the A/C off! (Imperative in order to figure out radiator issues - the HVAC heats the radiator usually in front of the engine coolant radiator and may give false readings especially when using IR gun or FLIR to evaluate the system.)

Does the upper radiator hose get warm/hot?

Does the hose to the heater-core get warm/hot?

Are "all" fluid levels topped up to the mark? (This includes inside the radiator when cold.)

I'd no longer drive that truck until the issue is solved. Can be many things. As it has also developed over time could as well be a blockage.
At best I'd start it and let run for less than 3 minutes at a time to diagnose. Then have it cool for at least 45 minutes.

At 70F outside temperature you may still have fog coming from the exhaust. But fog/haze is not dense and immediately should dissipate. Whereas a coolant leak into the exhaust usually produces white, grey smoke/fog which is rather dense. Some dripping from the exhaust is usually condensation. If it drips coolant through the exhaust most probably your radiator is empty.

I'd go about that by first checking all fluid levels and quality. Oil should look like oil, be smeary like oil and smell like oil. Coolant should be slight color red/green depending on the OEM indication, can smell like brackish water, foul smelling water or kind of sweet smell if rather new coolant.

Check all the hoses to and from the radiator to the water pump. Check the hoses to and from the heater core (aft of block to passenger side firewall and back along engine to water pump). Check hoses to the expansion tank.

Check radiator cap. Mostly all manufacturers use a two step cap. About 1 quarter turn unloads it, then you have to push down to release it another quarter turn to take the cap off. Has the cap been closed correctly? If not it would not pressurize the cooling system and it would overheat - or get to high temps. Need to push down when closing. I do close them by putting it on. Usually you have to slightly push down to clear the tabs on the radiator with those tabs on the cap. Then turn the first quarter turn, then push down and turn further until the stop.

Top radiator hose will get warm/hot once the thermostat opens, while the one at the back of the block to the heater core should always get warm as soon as the engine runs and warms up. During the warm up the radiator hoses should gradually build pressure and become stiffer/harder. When thermostat opens the upper one gets hot (thermostat should open around 190F). This would tell us that the thermostat is working as it should. Upper of radiator will get warm/hot as well. Lower part of radiator will eventually warm up as well. Shut engine down to check lower radiator hose. (DANGER: fans and belts) An alternative is an IR gun (a FLIR would be perfect).

If after a minute or so the lower part of the radiator does not increase in temperature (just increase is o.k. as the radiator is cooling, the outlet is never as hot as the inlet.) something through the radiator may be blocked.

 

My first thing was checking the thermostat since thats what fixed it last time. Saw a video about boiling water and throwing it in. It did open for that lol

Ive already thrown the Jimmy into a barn ready to start taking apart. I love driving this vehicle, I'm not trying to damage it!

Liquids have been constantly topped.

Upper radiator hose does get hot, havent checked the heater core hoses.

I do not offroad, I have a RWD
That being said all thats on my grille is a swarm of bugs from countryside driving. But I have not checked the radiator fans.

Clutch fan blade? There are surface cracks through it but they dont go through to the other side so its still together.

Sorry for the messy reply, now for what I found.

So I had a friend come whom works at Autozone (Doesnt say much but he'll know more than me lol) and first thing he did was smell the dipstick and oil cap.
Well... He said he smells coolant in the oil, oil is milky with white in it, I'm losing coolant without any sign of a leak, blah blah blah. He said he knows its a head gasket, but just because I don't want to start a big job without confirming thats it, I bought a compression tester.
If it is indeed a head gasket I feel like this'll be a good experience to learn more about the vehicle. Get used to taking this sucker apart.