What a HOT mess...

[Sodium Duck]

Here goes my epic story:

I bought my truck this past summer. I drove it about 75 miles home. For that ride, the temp stayed around 220 I'd say. I check out the cooling system when I got home, and found a bunch of brown sludge in the overflow tank and around the neck of the radiator cap. So I brought it to a shop to have them chemically flush it out, and while they were in there I had them throw a new thermostat in.

At that time, I was concerned there may be a blown head gasket - because of the sludge, and it would throw a little bit of white smoke when warming up. So they said they'd check something (I can't remember what) to see if there was mixing between the oil and antifreeze. Well, they said no and went ahead with the flush.

After that, truck would run okay. But what I started noticing was that it would begin to almost overheat (almost redlining) then go back to 210 and stay there.

So I figure, hey what the heck. I'll just bleed the system, maybe it's an air bubble. So I do. When I'm bleeding it, the truck starts heating up, almost overheating like it was doing, thermostat opens up, level in radiator drops, and I top it off. I figure, cool. That should solve the problem. Well, it doesn't. Still doing the same thing.

So I bleed it a few more times, with the same result. I did this over 3 days, 3 separate times. The only thing out of the ordinary, was the second time when I went to bleed it. The radiator started gushing coolant out. I turned the engine off, and it kept pouring out. I pretty much had to refill the whole system.

So I still have the problem, and I'm thinking of all the things it could be. So I go with the easiest and cheapest to fix. I guessed maybe the thermostat was junk, sticking, whatever. I go ahead and replace it.

Well, wouldn't you know it! I pull the thermostat housing off, and what do I see... a big spring. The shop installed the thermostat BACKWARDS. 

So I'm thinking, sweet. Easy fix, and the truck will be running great again. I put in a brand new thermostat (THE RIGHT FREAKING WAY...). And I figured while I was doing simple things like this, I may as well put a new radiator cap on. So I put a 16PSI vented cap on. Also replaced the upper radiator hose and clamps because the old one was leaking a little bit.

Well, to my surprise it didn't work. The truck isn't exactly over heating. But it is running hot STILL, around 240.

I also notice that my upper radiator hose is really soft. The coolant system has no pressure what so ever. The hose is screaming hot, and soft like butter.

So now I'm kind of back to square one. I don't know what to try next.

I'm thinking like water pump impeller is junk. Or maybe the radiator is clogged up, it is really old and the core looks rusty (maybe that's where the brown sludge came from?). Or maybe I really do have a blown head gasket... ugh.

No other major symptoms to note as of right now. Oil is clean. Coolant that was let out was clear. Weirdly enough, the overflow tank is brownish again. No plumes of white smoke during operation. Exhaust smells normal.

PS -- in between the chemical flush and myself finding the backward thermostat. I changed the oil. It came out black. No metal shavings. No foam. I noticed a sharp increase in my oil pressure. It was great, around 45+PSI. I now notice that it's much lower. Around 15-30PSI.

I'm lost. I should just build a 350 already and drop it in... 

[Captkaos]

What year truck?  Is this happening now in the cold or?  Going up to 210 isn't out of the ordinary on a TBI truck, the thermostat is 195 for them...  What does your Coolant level look like when it is dead cold?  Is it full or below the cap?

[Sodium Duck]

Specifics on the truck are in my signature. It's an 85.

It's happening right now, yea. Probably like 40 out today.

It's going up to 240, not 210.

I used a 192 thermostat for whatever that's worth lol.

When I took the radiator cap off today, after it sat all night, dead cold - it was full.

[1980c10]

Are you over heating at idle or while moving down the road?

[87454westernhauler]

do u have an aditional temp gage or just the stock one on the left side of the head? The stock gauge on my 87 454 is always showing that it is overheating or runing from 210-240 and is not very acurate, but i have an add on water temp gage that is right on the water pump and always reads 190. does yours once it worms up stay right at 240 all the time?

[Red 83]

My '83 C10 has an '84 crate 305 in it. I had aftermarket temp and oil gauges installed the same time as the engine. I have noticed that my temp gauge goes up to 225-230 before the t-stat opens, then it drops down to 210-215 where it stays while driving. I always thought that was normal, but now, after reading what the guys are saying here, maybe there's something wrong with mine too.

Also, mine runs 40 psi oil pressure at operating temp.

I'd say check the water pump and oil pump.

[Captkaos]

Is your reservoir "full" when hot or cold?
If you pull the cap off is water moving?
Do you happen to have a aftermarket gauge you could hook up?
Your gauge should have 100, tick(155), 210, tick(235), 260.  And yours is past the tick after 210?

[87454westernhauler]

i wouldnt be to woried about the oil pressure. the pressure will generaly get lower when it needs changed as it gets thiner and go back up after u change it.

[Sodium Duck]

**Are you over heating at idle or while moving down the road?
The engine heats up, and keeps heating up until it gets to around 240. Driving and idle. That's just where the temp sticks now.

**do u have an aditional temp gage or just the stock one on the left side of the head? The stock gauge on my 87 454 is always showing that it is overheating or runing from 210-240 and is not very acurate, but i have an add on water temp gage that is right on the water pump and always reads 190. does yours once it worms up stay right at 240 all the time?
Stock temp sensor on the block. Yea, it stays at 240.

Do they make a water pump already drilled and tapped for a temp sensor, or do I have to modify the pump myself? I would like to try that.

**Is your reservoir "full" when hot or cold?
The overflow reservoir doesn't change much. It's stays at the same level. I don't notice it change.

**If you pull the cap off is water moving?
It looks kind of stagnant. I'm not sure what it should look like though. It's definitely not whirring around in there.

**Do you happen to have a aftermarket gauge you could hook up?
I don't. But like I said above, I'd like to put one on a new water pump. I can drill and tap one myself, but I'd like to pay for the convenience if they make ones pre-drilled for it.

**Your gauge should have 100, tick(155), 210, tick(235), 260.  And yours is past the tick after 210?
The pic is the gauge I have. I made a red line showing where the engine gets up to and stays at.

[Captkaos]

That is 235 degrees.
for an aftermarket gauge, you just need to remove the fitting from the opposite side of where the stock one is, or from the intake manifold.
Fluid should be moving if you remove the cap.

[1980c10]

You said you're not losing coolant but reading 240 degrees. This makes me suspect your gauge is reading wrong. Do you have any signs of overheating other than the gauge reading hot? can you hear the coolant bubbling? May be your gauge but more likely the sensor.
Also check the weep holes on your water pump just in case.

[Sodium Duck]

I picked up a cheapo sunpro gauge. It has the sender built in and all that. I'm going to test the accuracy of it a little later tonight with a pot of boiling water... I'm a bit dubious of it, as it only cost 17 bucks...

It was either that or buy a new temp sensor for 12 bucks. I figured if the gauge was broken, at lease this would be half way decent and work for a short time.

I also bought a new water pump. I'm thinking about trying to drill and tap it and put the new sender on it. Or should I just use the stock location on the side of the head?

[1980c10]

Just use the stock location.

[Sodium Duck]

Where's your sense of adventure... lol

[Skunksmash]

do u have an aditional temp gage or just the stock one on the left side of the head? The stock gauge on my 87 454 is always showing that it is overheating or runing from 210-240 and is not very acurate, but i have an add on water temp gage that is right on the water pump and always reads 190. does yours once it worms up stay right at 240 all the time?

I'm currently in the process of replacing that stock piece of garbage with a digital gauge for this very reason in my TBI truck. It kept saying the truck was running about 155, for the longest time I thought that was true. Till I hook up my code reader and it says its really at about 190. Way too big a difference to be tolerated. If it ever went to over heat, you'd never know it. So to the OP, yeah I'd definitely confirm that its really running at what it says it is.