Cool Down!

[crashz]

What have you guys done to cool the 6.2L in your rigs?

I have some major hills surrounding the farm where I keep the 87 in my signature. Last weekend I took the 87 out and had to climb a fairly steep, consistant grade. As it was fairly warm last weekend (high 80's) the truck was holding a consistant 200 degrees before ascending the mountain. From what I gather here, 200 degrees is normal operating temps. Once on the grade, the truck had to downshift to second and was screaming along at about 35 mph with a light black smoke out of the tail pipes. Keep in mind, it weighs about 8000 lbs empty (which it was empty) and is shaped like a brick with a big steel sail.

Temp (on the factory guage) climbed to what I estimate 220 - 225. It was about halfway between 200 and 240 (red). On the downhill, it cooled back off, and once at the bottom, it was down to about 180-190. I feel that this was too hot.

What have you guys done to cool your rigs down?

My thoughts are to separate the coolers. I'd like to eliminate the extra heat generated by the transmission and oil coolers within the radiator, by plumbing external coolers in. Maybe in a protective housing within or below the bumper.

Since it appears that the cooling system is operating at 190-200 degrees, I assume it has a 195 degree thermostat. Could dropping a 180 degree T-stat help?

I'm going to flush and fill the cooling system this summer as well as change the hoses. The antifreeze doesn't look to bad and I know it had been changed out by the previous owner when he replaced the cab. He left the orginal hoses though...:rolleyes:

BTW - I turned the heat on full to help cool the truck and it was definately hot, but not burning hot. I'm thinking after 23 years, the factory guage is probably not very accurate either.

[Edahall]

One good place to start is the fan clutch. Does it work? They're kind of a high failure item and is much needed for proper cooling especially if you're pulling hard and at slower speeds when not much air is flowing throught the radiator. For comparisons sake, I used to pull my 26 ft Airstream weighing 5000 lbs with my 82 Diesel Suburban with 3.08 axles. The combined weight was probably around 11000 lbs. If I kept the speeds above 45 mph on the grades, the temperatures would stay pretty constant. But sometimes, I would get behind a slow vehicle and would be down to 30 mph and I would notice the temperature gauge blip up a small amount. I used a big transmission cooler and kept the torque converter locked up as much as possible. At 30 mph, I would have to unlock to prevent from lugging the engine.

[crashz]

I'm not sure. I didn't check. Since this truck is not very easy on fuel anyway, would it be better (and cheaper) to just run a spacer and keep the fan locked on all the time?

[DmaxMaverick]

If it's a V-belt accessory drive, get your hands on a HMMWV fan clutch. They are hydraulic, and can be operated by a thermostat, switch, or both. On when you need it, off when you don't.

[john8662]

Three things that keep my 6.2L cool are:

Only a high-flow Robertshaw 180 stat.
Visteon Aluminum two-row (3/4" tubes) radiator for 6.2 application
Working factory fan clutch (this is tricky getting a "good" one).

The 1991 Suburban in the signature with just a stock EGR 6.2L has pulled more weight than any other vehicle I've owned. Stupidly over weight capacity. Pull full throttle with the A/C on most time. I think I know why the TH700 is on strike with me now :rolleyes:

Pulled 10k behind it...

[NH2112]

This is kind of funny because with the exception of an armored humvee I drove while in Germany (the grille armor disrupted airflow and even in winter it ran hot), I never had cooling issues with a 6.2l. My last 6.2l truck had maybe 25% of its radiator fins left, but never came close to overheating even though I worked that truck HARD. My first 6.2l truck had a much better radiator but it still never overheated regardless of what I did. When I first got it it had a 700R4, and hauling another fullsize pickup on a trailer the ATF temp barely got warm to the touch. In fact, I never even had the fan clutch kick on with either of them, and at one time I was concerned that it wasn't working and my gauge was inaccurate so I ran the thermocouple for my DVOM under the upper radiator hose at the t-stat gooseneck and monitored coolant temp. The 180-degree T-stat actually opened around 175, and the highest coolant temp I saw over a couple days of driving was 184 (it impressed me enough to have stuck with me for 7 or 8 years now LOL.)

It's my opinion that these trucks have WAY more cooling capacity than they need. The same goes for my F350 w/7.3l, especially with the new aluminum radiator.

[raunch]

I've been looking around some and haven't been able to find a high-flow water pump for v-belt 6.2.

Is there one available?

[NH2112]

I'm pretty sure Peninsular makes a 100gpm V-belt pump but I highly doubt that's the 6.2l radiator's ideal flow rate, which means coolant will either flow through too quickly to pick up the maximum amount of heat, or the radiator may be a bottleneck and not allow the coolant to flow through quickly enough to draw heat away. If you upgrade one part of the system you'll generally have to upgrade the rest of it to make efficient use of the greater capacity.

[bleucrew6.2]

I'm interested in hearing more about this thread, especially the fan clutch and how I can test it. Is the fan that important when running highway speeds? I've never seen my temp much over 200 degrees until last week returning from West Virginnia. Radiator is new, water pump is new, stat is Delco 190. I've never had this problem before. Seeing temp just over 220 freaked me out. I replaced the engine in early March, and have had no problems at all until now.

John

[mvtofino]

Great thread - great timing!

Reading these posts might have turned the lights on in my head. For the last month or so I have been struggling with a combined faulty alternator issue that fried my glow plug controller (twice I might add!) which in turned caused other problems downstream and the expensive replacement of g/p controller, g/p relay, installation of a manual bypass switch blah blah blah. Approximate cost so far is over $2,000. Choke. Not a happy camper...

We just completed a 16 night, 2,400 mile trip from Vancouver to San Francisco in our 1983 Pace Arrow motor home with the Chevy P30 chassis, a 6.2 liter "J" code, a THM400, and 4.10 rear end. The chassis had 53,000 original miles at departure, and we have upgraded/replaced most of the mechanical components, appliances etc. since buying it last year. It was a terrific vehicle for the trip, and she ran perfectly once the known problems were addressed (as best we could - please read on).

Or so I thought. One issue remains unresolved - we frequently have to deal with/listen to some horrific fan belt screaching on initial start up with a cold engine, and what's worse, it will also screach on start up with the engine at full operating temperature, or anywhere in between. What makes it difficult to diagnose is the inconsistency of it. It's a sometimes proposition - not an all the time situation.

It first began this May when we prepped the vehicle for the trip. The brand new alternator installed last August was faulty, and it was replaced under warranty. A new water pump/P Steering belt was installed at that time.

When the screaching began, I assumed the alternator/a.c. belt wasn't tensioned right, and had the shop re-tighten it. It would be fine for a couple days or a few miles, and then it would start screaching again.

We returned it to the shop 3 more times for re-tightening, then to a second shop for a second opinion and they re-tightened it, then 30 miles into our trip, the AAA Emergency Road Service re-tightened it, and 30 miles after that, the Chevy/RV Dealership in Mt. Vernon installed a new alternator belt (and the g/p relay and bypass switch etc.).

But it continues to screach, screach and screach! Sometimes it is torturous listening to it... other times it's a few squeeks like you'll often hear when you rev a performance motor - like you've just woken the belt up or something.

I've pulled my hair out trying to figure the problem out. I've had no fewer than 4 different professional mechanical shops/services investigate the problem and give it 2 thumbs up. I've written a number of threads on a couple of diesel webpage forums detailing the problem and assimilating the information/advice/commentary etc.

And the collective knowledge of all those resources still hasn't solved the problem. Don't get me wrong here - I'm not blaming anybody - it's my problem, and I am thankful for all the help & assistance I've received so far.

But the question remains: What have we missed? What could it possibly be? Hell, I'm a retired financial consultant and no mechanic by any stretch of the imagination - so what do I know. But this is no different than solving a simple tax problem, for example, for a client - it requires "thinking" and often means thinking outside the box (to borrow an overused cliche...).

The new posting notification in my inbox brought me to this thread. In reading the posts about cooling the 6.2l, the penny finally drops and like a hot wind zephyr down the valley that sucks you off the fence-rail I say to myself "...a fan clutch? Could the root problem be the fan and clutch mechanism? (I don't know the all parts, but I understand the concept & theory) Maybe it isn't fully engaging or disengaging when energized/de-energized. It would certainly suit some of the symptoms I've been listening to. Need to investigate further!"

Put another way, could what I have been listening to and assuming to be a V-belt tensioning issue is, in reality, a faulty or worn fan clutch mechanism? I know I have been fooled in the past when a water pump has failed and lead me to believe it too was a slipping or worn v-belt by mistake. If you don't feel the vibration, the two can sound awful similiar.

But why haven't the dots been connected? Surely this has happened to others at some point in the billions of miles logged over the years. Or is it such a preposterous idea that only someone as ignorant as me would think of it?

Mind you, my cooling system works perfectly. If anything, the mechanical aftermarket water temperature guage reads too cool - a consistent 160 degrees 99% of the time. There are some long, steep (7 and 8 degree inclines) hills on Interstate I-5 and Hwy 101 down the Oregon & Northern California coasts, not to mention some of those lengendary hills in San Francisco that have you gazing at the stars as you climb them locked in first gear and hoping you don't slide backwards if you slow down or stop!

And our 13,000+ pound vehicle, in 85 degree ambient temperature never once went past 200 degrees of water temp, or 190 dgrees of oil temp, and the tranny fluid temp moved a maximum of only 3 needle widths at the hottest and hardest working times. One would think that a faulty or worn fan clutch would be doing most of its screaming with these more demanding loads and operating conditions. But no - not even a wimper of discomfort or hint of overheating whatsoever.

As usual, this has become another lengthy posting - more an indication of my frustration and need to vent than anything else. Sorry about that. So thanks for staying with me this far.

Am I nuts? Could the fan clutch be the culprit? What do you guys think? How would I test this without having to mortgage my house? What else could it possibly be? Surely you can only tighten a v-belt so much, right?

An early Cheech & Chong comedy line had "The Hippie Dave" suggest to "The Man" troubleshooting a stalled engine on the side of the road if "...he'd checked the air in the tires lately?" I hope I'm not as clueless as that ;>)

Anyway - Please help put me out of my misery, and reply with your thoughts, advice and comments. Thanks again for listening!

JT

[crashz]

Hey JT,

I'm going to throw out an idea that was told to me by the mechanical shop that rebuilt the bolower unit for my furnace. We had a horrible screech to the blower and after tightening the belts and lubing the bearings, it was still there, though everything turned freely with no noticable bind or wear. They mentioned that the pulleys wear also, and a slipiing belt will wear a pulley prematurely. Even if no visible wear is noticed. Sure enough, after cleaning and adding two new pulleys, the screech went away for good. Maybe your pulleys are worn?

You also may be onto something with the fan clutch. If that remains locked, it would draw a significant amount of power through the V belts to turn it at start-up. But if it cools as good as you say, you may not want to chance "unlocking" it.

[argo]

Even if no visible wear is noticed. Sure enough, after cleaning and adding two new pulleys, the screech went away for good. Maybe your pulleys are worn?

Good point. I have seen this in the past. When the pulleys wear, the groove gets wider, and the belt's "bottom" contacts the bottom of the pulley grove. V belts are designed to drive on the sides, not the bottom. I haven't seen this much in automotive applications, but I used to work on mowers (Alamo/Mott and Woods decks) on DelDOT's tractors when I worked there, and it was a problem for some of them, especially mowers that operated under dusty conditions allot.

[crashz]

Update:

Well sort of an update. While chasing a fuel leak, I found a major crack in the frame at the front cross member/engine cradle. This area was repaired (poorly) once before with a patch plate due to a collosion (9' snow plow vs catch basin inlet).

I tore down the nose of the truck so that full access to the frame could be had and a proper repair made. In my quest, I brought the radiator and support home for some freshening up with a cleaning and some paint. The radiator appears new on the outside, but the interals are surprisingly caked with white build-up. Flushing with a hose revealed about a cup and a half of sludge, rust flakes, soft white precipate, and oddly enough some copper looking particles. The copper looks for be a sealant like Bars Stopaleak or something. It also looks to be a two core unit. Once the prognosis is made and the frame issue resolved, I'll either have this radiator cleaned & rebuilt as a four core, or purchase a new radiator. Looks like I'll be removing the heater core as well.

The good news here is that while the nose of the truck is off, I can easily replace the glow plugs and return hoses!

[argo]

The good news here is that while the nose of the truck is off, I can easily replace the glow plugs and return hoses!

Always an upside!