Overheating and A/C failure. (RESOLVED)

[BSalty]

Ok after searching my thought is that I need a new fan clutch but wanted to run it past you guys before I start ordering parts.

Symptoms:

Fan has been roaring most of this summer on hot days at start up, obviously needs a new clutch but last time I was able to go almost a year without problems before replacing it, it would roar until I hit 20-30 mph and turn off and run fine, doing the same thing this time. Also had and intermittent SES last time, ended up being a bad thermostat which was replaced in fall 2009. No codes this time. I also flushed the coolant at the same time.

Thursday: Drove to the top of a paved canyon at very slow speeds 25ish MPH on a steep incline for roughly 25-30 min. When I parked at the top it started boiling w/in 2 min of parking. Turned the truck on and held the RPMs around 2k, cooled right off let it idle for 3-4 min and had no problems.

Friday: Drove 15 miles city, parked and noticed the engine temps rising. Got it cooled down again, no boiling over this time. 30 min later made a quick trip to the corner gas station, A/C was blowing hot air and engine temps spiking again.

When I got back home here is what I checked:

1: Felt the AC tank, it was hot.
2: AC and Fan fuses, both were good.
3: Checked the radiator for obstructions and other than some bugs it looks clean.
4: Hooked my gauge up and the R134 is slightly overcharged at idle. (Normal)
5: AC pump is cycling, I can hear it click and the RPMs would drop slightly.
6: Checked the oil, didn't see any water on the dipstick or bubbles in the oil.
7: Hooked up my scan tool and didn't find any stored codes.

After I pulled and checked the fuses I restarted the truck to check the R134 pressure and the AC was working fine again. I haven't driven it yet since then.

I know these trucks have the safety shutoff on the AC for overheating protection, so I am assuming that is what happened there.

With no SES light and no stored codes I am wanting opinions before I start shot gunning parts at it.

Fan Clutch, Rad cap, thermostat are my next options, in that order.

TIA.

[djthumper]

Man I would be more temped to try the radiator cap first. It is the cheapest and easiest part to replace that probably has not been replaced.

[The Roadie]

When the dash gauge was over 220-230 degrees, and you were at 2000 RPM to cool it off, was the fan clutch fully engaged? Were you able to lift the hood and watch or feel the airflow?

[BSalty]

Yes it is pulling hot air through. Fully engaged, maybe, but pulling air through pretty good. It was blowing super hot air enough that I was feeling it pretty good half sitting in the seat with my leg out while keeping the RPMs up with the hood up.

As to the cap, AFAIK it is the original. 112k miles. you may have a good idea. Seems like they were $40ish last time I checked.

[Trail X]

I'm in agreement on the cap. Quick to replace, and I'm also unsure if the computer has a way to check the coolant pressure.

If it's the fan clutch, you'd think it would throw a code.

I assume your scanner cannot read actual coolant temps?

[The Roadie]

... if the computer has a way to check the coolant pressure....

It does not. A 50c sensor that the GM designers omitted to make sure the dealers had more customers coming to them in the long run to check cooling system pressure. Well, honestly, I have no idea WHY they decide half the things they decide on.

[BSalty]

Ok y'all talked me into it, I will try the cap first. James, no my scanner is one of the really cheap ones. It will only read stored or current codes. It won't even clear the codes. Dang OBD2......

I did forget to mention I also changed the temp sensor when I did the thermostat. The one in the head right next to the thermostat housing.

I will get the cap tomorrow and see if that is the problem, If not I guess I have a trail spare.

[BSalty]

Well I think the cap was the issue. Replaced it $7.95 from Napa. Drove it for 20 min in slow city traffic, let it idle for 5 min with the A/C running. Gauge never even touched 210 and its 97 degrees outside today. Also noticed that my drivers front tire was a bit low, it was at 29 lbs, I normally run 36 psi. So maybe the heat, slow driving, low tire pressure on a curvy road, and the fan clutch all were too much for the cap.

Anyhow this is resolved now I think.

Thanks for the advice on the cap guys. Kind of saved my can, I need front and rear brakes for inspection this month and the $ needs to go to that instead of the fan clutch right now.

[djthumper]

That is good to know. I hope that is all it was. Simple and cheap is always a good repair.