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Overheating..Drawing a blank UPDATE #2

Grim-Reaper

Grim-Reaper

3/4 ton status
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My 88 R20 454 Burb. Only overheats with the A/C on stuck in traffic. Runs warm at Hwy speeds with A/C. Runs fine with the A/C off.

New Thermostat, 195 deg
Most of the coolant has been changed. Running about 40% antifreez with Prolong stuff that is like water wetter.
New Thermostatic clutch on the fan. Seems to move plenty of air. Shroude is in place.

HD AUX tranny cooler. Transmission is not over heating. Lines are relatively cool as is the pan. Well within normal operating temps.

Seems to hold plenty of pressure, Hoses are nice and hard when at opperating temps so cap appears fine. No coolant loss.
No bubbling in the radiator so no indication of blown head gasket.

Has a 4 core radiator that looking down the inside appears pretty clean. Minimal deposits.

PO had replaced the water pump about 5k ago.

New O2 Sensor and no codes on the computer.

I'm at a loss. Never had anything give me this sort of problem that the above work didn't cure.

Only things I can come up with is The A/C is putting excessive drag (It's been converted to R134) or my cat is getting plugged and the A/C is just enough to put it over the edge. I'll probably pull that cat this week.

Anything I'm missing here? We planned to take this truck to the beach in 2 weeks. I have to get this cured.


<font color="red"> See update below please </font>
 
Re: Overheating..Drawing a blank

Is that new clutch a Delco or an aftermarket? I have had nothing but problems with aftermarket not working as good as the HD Delco. Another thing, what type of fan are you running, and how many blades? And the 3rd thing is that it is possible that your radiator is causing it. I was talking to a radiator designer about a radiator for my k5 and told him I wanted a 4 core. He told me that people were having problems with them overheating because of how thick the radiator is, so they made the 4 core replacement a high flow 3 core, and the normal 3 core a high flow 2 core. I have run his high flow 3 cores in both my old 87 suburban and now in my k5 and have never had a overheating problem. I also run a HD delco clutch and a factory 7 blade fan.

Dan
 
Re: Overheating..Drawing a blank

ok so i would suggest a 160 t-stat and this...
how are the fins on the radiator? dented at all, blocking air flow if they are..cheap easy fix to straighten the fins, like a 12 dollar tool...big block with a 195 stat seems awful high to me..but i dont know for sure...
 
Re: Overheating..Drawing a blank

Even though your system seems to be holding pressure, have the cap pressure tested.
 
Re: Overheating..Drawing a blank

Be careful on putting a really low thermostat in. One that is too low can actually cause a overheating problem. It doesnt allow the radiator to do its job correctly and caused it to overheat.

Dan
 
Re: Overheating..Drawing a blank

[ QUOTE ]
ok so i would suggest a 160 t-stat and this...
how are the fins on the radiator? dented at all, blocking air flow if they are..cheap easy fix to straighten the fins, like a 12 dollar tool...big block with a 195 stat seems awful high to me..but i dont know for sure...

[/ QUOTE ]
The rating on a thermostat is what temp it should be fully open. A 160 degree thermostat is not going to fix a problem where I'm hitting 220degrees. 195 is Spec for ANY fuel injected GM truck. With A/C off I run a dead steady 200Degrees in traffic and that is what GM says it should run. I'm running about 190degrees with A/C off going down the road at 60MPH. That temp thermostat is to make sure the vehicle goes into closed loop operation.
 
Re: Overheating..Drawing a blank

Ya, On the t-stat go no less than 180... I was told by a very reputable Chevy engine builder to not go any lower and that the 160's dont let the coolant stay in the rad long enough to cool....

Do you possibly have air in the system?

One other thing that I can think of, do you have the right direction fan? a friend of mine who had my 89 p/u before me got a new fan for it and they gave him a fan for an app. without a serpentine setup so the blades were angled the wrong way... Just something to double check.
 
Re: Overheating..Drawing a blank

[ QUOTE ]
Is that new clutch a Delco or an aftermarket? I have had nothing but problems with aftermarket not working as good as the HD Delco. Another thing, what type of fan are you running, and how many blades? And the 3rd thing is that it is possible that your radiator is causing it. I was talking to a radiator designer about a radiator for my k5 and told him I wanted a 4 core. He told me that people were having problems with them overheating because of how thick the radiator is, so they made the 4 core replacement a high flow 3 core, and the normal 3 core a high flow 2 core. I have run his high flow 3 cores in both my old 87 suburban and now in my k5 and have never had a overheating problem. I also run a HD delco clutch and a factory 7 blade fan.

Dan

[/ QUOTE ]

Truck is bone stock with 74,000 original miles. Factory orignal 4 core and 7 blade fan. Previous owner took good care of it.

That does make a lot of sense with the radiator. I'll put that on my possible problems list.

Autozone clutch. It does seems to come on earlier and stronger then the clutch it replaced but it's possible it has a problem. I'll look into that as well.
 
Re: Overheating..Drawing a blank

[ QUOTE ]
Ya, On the t-stat go no less than 180... I was told by a very reputable Chevy engine builder to not go any lower and that the 160's dont let the coolant stay in the rad long enough to cool....

Do you possibly have air in the system?

One other thing that I can think of, do you have the right direction fan? a friend of mine who had my 89 p/u before me got a new fan for it and they gave him a fan for an app. without a serpentine setup so the blades were angled the wrong way... Just something to double check.

[/ QUOTE ]

I'll double check the fan but that does bring up a good point. The water pump has been changed...wonder if they put the wrong WATER pump in Was done not long before I bought it.). /forums/images/graemlins/confused.gif

How the heck could I check that without pulling it off and looking at the blades?

Yep it has a Air pump for emmisions. Had the belt off and it didn't seem to have any unusual drag on it.
 
Re: Overheating..Drawing a blank

I'd be more inclined to believe the radiator isn't up to par.

I'm sure you know my stance on cooling, more coolant flow is better, period.

I've never seen a water pump not work correctly. Even when the seals fail, they still work. I've heard of the impeller pulling off of the shaft, but only on my buddies race car with a POS flex fan. Even then it still works, just makes noise as the shaft starts wobbling. Reverse rotation water pumps have been used for the wrong vehicles, so that COULD be an option, but I fail to see how the engine would EVER cool while cruising, since it's moving coolant if the temperature goes down.

Can you get the radiator flow tested for free?

Of course with only 5 or so problem sources we can think of, it's bound to be something totally different. /forums/images/graemlins/smile.gif
 
Re: Overheating..Drawing a blank

Is the A/C condensor in front of the radiator? If so, check it for clearance and dirtiness. I've noticed that my Cherokee would overheat when I had the a/c on, on a hot day. I replaced pretty much everything and what actually did the trick was when I cleaned out the fins on the a/c condensor. They had bugs and crud in them. I waited until I noticed the overheating problem and went and checked the front. The condensor actually gets a little cold and expands, therefor sealing up if dirty and blocking significant air flow.

Might want to check that out.
 
Re: Overheating..Drawing a blank

I will check with a friend of mine who is a GM Tech to see if there is any way to tell externally if it is the right pump...
 
Re: Overheating..Drawing a blank

Can't you check the coolant flow direction out of the pump by squeezing the lower rediator hose? That should tell you if it's pushing or pulling.
Also, what type of metal is your rad. made out of? I think aluminum has the best cooling properties.
 
Re: Overheating..Drawing a blank

[ QUOTE ]
Is the A/C condensor in front of the radiator? If so, check it for clearance and dirtiness.

[/ QUOTE ]

If yer complaining about overheating and haven't done a basic inspection, to include that check, before posting, you aren't qualified to be working on your own vehicle. /forums/images/graemlins/tongue.gif
 
Re: Overheating..Drawing a blank

[ QUOTE ]
[ QUOTE ]
Is the A/C condensor in front of the radiator? If so, check it for clearance and dirtiness.

[/ QUOTE ]

If yer complaining about overheating and haven't done a basic inspection, to include that check, before posting, you aren't qualified to be working on your own vehicle. /forums/images/graemlins/tongue.gif



[/ QUOTE ]

You'd be surprised at how often that is overlooked. He stated looking at everything else but that, so I suggested it. No matter how obvious it was. Most unsolved problems often have the most simplest solutions.
 
Re: Overheating..Drawing a blank

[ QUOTE ]
He stated looking at everything else but that, so I suggested it.

[/ QUOTE ]

No offense intended in my reply, it was kind of in reference to how long Grim has been around, and this has come up before multiple times (as have so many other things) so I'd have hoped he had already done a check on it.

But seriously, I wasn't implying your idea was a waste of time or anything. The radiator exterior should certainly not be blocked up with garbage.
 
Re: Overheating..Drawing a blank

No worries, I didn't sense anything negative from your post at all. /forums/images/graemlins/smile.gif
 
Re: Overheating..Drawing a blank UPDATE Electrical people please read.

Well today I noticed something else. Might be related and I might not be overheating at all. /forums/images/graemlins/confused.gif

I think the Altternator is dying. With the long day's I haven't needed the headlights in a while. Today I noticed the head ligts flashing. Last week I have been getting whine in CB.

For a long time the Volt gage reads low. Been like that since I have owned it.
At the battery at idle with a $180 Fluke meter I was showing 13.4 volts and the gage showing around 12. Inside at the cig plug I was showing 13.3. So I ignored it.

Well after the thermostat and water wetter stuff The temp stayed steady 190-195 on the way to work but 75degrees this morning. On the way home with the A/C on it started heating up.
It's raining so Had the lights and wipers going as well. Pretty good load on the alternator. Halfway home I'm starting to heat up. tun off the A/C and it held about 215 all the ay home. Pull in the driveway throw it in neutral and bring up the RPM's. I park nosed up to the Airstream and flickering headlights catch my eye in the reflection. look at the volt gage and it's reading little over 13v (it's normaly showing 12.). Flip on the dome lights and they are flickerin at 1200 RPM or so.

So what would a temp gage do if it's getting too high of voltage or a diode ate it and it was getting A/C voltage?

Pouring down rain. So can't mess with it till tomorrow.
 
Re: Overheating..Drawing a blank UPDATE Electrical people please read.

FWIW, my voltage fluctuates between 12 and 14 (which is pretty common with stock alternators) and it has never affected my gauges.
 
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