MUNDANE MAINTENANCE - Cooling System

[phantomjock]

This not an exciting "MOD," but something that ought to be of some interest.
Seems everyone is anxious when buying a used ClassB to get all the maintenance records. Good plan, even for the purchase of any used vehicle. We did so when we bougfht ours too.

I'll admit, mine was a cursory look when we purchased, but it was easy to see the previous owners used service facilities, rather than DIY. I'm keeping a log of my maintenance, and assume many of you are as well. But that is not the prupose of this thread.

I recently got an (engine) overheat. Not too drastic, but enough to cause concern. Now I'm going through the system. Radiator pressure checked good and held for over 3 hours before I terminated the test.
Next I'll check for combusion gasses in the coolant (indicates a head gasket fail). Not suspecting such as we get no white smoke at the tail pipe, but a caution worthy of noting.

Then I plan to do a complete flush of the system. As I am getting ready, I took a second moment to go through the vehicle records. To my surprise, there is no indication a coolant flush has ever been accomplished - the vehicle is 16 years old! Given the Chevy Owner's Manual recommendations, it should happen every 150,000 miles (now just at 92K) - OR every 5 Years, WHICHEVER occurrs FIRST. So, there should be record of 3, or at least 2. So, I think its time to flush the system.

But, because I can overthink things, I recall waterpumps are good for about 100K. Having searched the forum, all but one thread is about the household waterpump - not the engine. I am reaching a cost/benefit decision point. I almost seems I should just go ahead and replace the waterpump as PM and not risk tossing a complete round of coolant. [NOTE: A waterpump for the Chevy 6.0L runs around the same price as a complete flush of coolant.]

Any experience here? Anyone replaced an engine waterpump? It's not a hard task, I am just interested at about what point you might have done so, 100K, 150K, never? If you did replace, what pump did you use? Also if you are "generaly" following the OEM guidelines for coolant flush?

Thanks in Advance!

Cheers - Jim

[avanti]

Time-based fluid replacement is a controversial topic. It is very difficult to point to any science-based support for such recommendations. (Brake fluid is an exception, due to moisture absorption). A lot of us believe that they are intended more to help dealers than to help vehicles.

FWIW: The OEM service recommendations for my MY2022 Ford Transit calls for coolant replacement at 200,000 miles, regardless of time. This is not atypical of modern vehicles and coolant formulations.

[phantomjock]

Understood. And with regard to GM products, there a was a period where the perscribed coolant of record dex-cool was highly disrepected. Apparently they have improved their formulation.

Waterpumps are a different issue. The 100K is perhaps a conservative estimate for life span. But, from my previous life experience, I'd rather have swapped a pump 10-20K before a possible failure point (unknown of course) than have a failure in the OUTBACK. It is Schrödinger's cat.

Uh-oh. I may have just convinced myself to go get that pump! On with testing!

Cheers - Jim

[phantomjock]

COMBUSTION GAS IN COOLANT

This is a simple test to make. I lets you see if you have a Head Gasket leak and combustion gasses getting into the coolant system. It doesn't always work - but is quick and easy. It had been some time since I did one, so when it took more than a few squeezes on the bulb - I was disappointed. No - PO'ed. It seemed I was getting an indication of the Blue Test Fluid turning YELLOW. That is a sure sign of a blown head gasket.

But, the more I squeezed, the more relaxed I became. I was sucking up the Dex-cool into the test chamber! WHEW.


Huraah! Take Head Gasket off the LIST of things to do!

BUT...

I let the engine idle for about 10-15 minutes. Electric fans doing their job. I now am suspicious that I may have a stuck thermostat. As I let the engine temp (gauge on dash) rise to 215-218, I recorded the upper and lower radiator hoses. Upper Hose read 168F, and the Lower 105F. That is a pretty big delta, so I am expecting a thermostat problem. It doesnt rule out a water pump, but both jobs call for draining the system. So, I'm moving closer to ordering a waterpump. I already have a new thermostat.

[booster]

What conditions did the overheat occur in? The 4L80E units are prone to overheating in tough conditions like long steep hills or sever stop and go.

[peteco]

A concern on replacing the water pump: you don't know what quality you will get with a new pump, even OEM. So many new parts are of lesser quality than those of years ago, as many are not made in US any more. Even US made ones may be of lesser quality as the push for cost cutting has reached far into many areas. I think the original pump in the 6.0 is very good quality and not known for failures. I think you should stay with it unless it shows evidence of impending failure.

[phantomjock]

booster-

Just "pushing it" in the heat on a back range road. No hills just a bunch of ruts. Motive was to get a "qualitative" feel [butt sensor] before the suspension effort. Then the heat rise. Not towing, but that will be th emajor effort of this wvehicle. So at some point I'll work in a transmission cooler enhancement too.

peteco -

All copied. And very good advice. Tomorrow is "check the cabin heat." If it is not heating - then the problem should clearly be the thermostat. I'll do that and flush the radiator and heater, etc. and reassemble. I'm going to pulse the Chevy forums on waterpump recommendations too for data. I note at least one user got only 30K with the cheap replacements!

While I have no indication of impending waterpump failure, I'm trying to eliminate all possible factors and build a reasonable work plan. But then again, plans can go sideways too!

Cheers - Jim

[booster]

Originally Posted by phantomjock

booster-

Just "pushing it" in the heat on a back range road. No hills just a bunch of ruts. Motive was to get a "qualitative" feel [butt sensor] before the suspension effort. Then the heat rise. Not towing, but that will be th emajor effort of this wvehicle. So at some point I'll work in a transmission cooler enhancement too.

peteco -

All copied. And very good advice. Tomorrow is "check the cabin heat." If it is not heating - then the problem should clearly be the thermostat. I'll do that and flush the radiator and heater, etc. and reassemble. I'm going to pulse the Chevy forums on waterpump recommendations too for data. I note at least one user got only 30K with the cheap replacements!

While I have no indication of impending waterpump failure, I'm trying to eliminate all possible factors and build a reasonable work plan. But then again, plans can go sideways too!

Cheers - Jim

When you pull the old waterpump, you may find the impeller is a big ball of rust. Think rust that looks like it was pumping salt water. That is what the one on my 96 Roadmaster looked liked. Based on what I saw come out of the knock sensor holes, nothing, I new it had or had in the past, the dreaded GM Dexcool sludge issue. I had to poke out a hole in it to even get the block to drain. I was suspicious when I got it as it had a new radiator in it.


I don't know if it has been improved much or not, but historically when it gets too old the PH changes and it starts doing galvanic corrosion between the metals in the engine, causing the "rusty" looking sludge and surfaces.


I changed our van over to GO5 style antifreeze even before the warranty was up on it, and the Buick as soon as I got it and found the issues.


If you were on a rutty road the trans was probably in a gear/rpm combo that had the converter unlocked, and that is an almost certain way to get them to overheat.



Since you are going to tow, you might want to just switch to the previous generation 8.1/454 engine radiator. It takes a bit of a mod, but not bad at all and the cooling gets much better at speed, not as much at low speeds/unlocked converter.

[phantomjock]

booster -
I figured you had been down this track before. Good advise on the radiator mod and the waterpump check. I really suspect the thermostat and will confirm today. And, your experience leads me to a next step. I will remove the waterpump and give it look over. Replacement would still be an option. I'll need to some more research there.

Cheers - Jim

[phantomjock]

Working the issues. So far have drained and flushed the radiator. Pleasing results - no nasty sludge. Some crud in the drained fluid from the radiator and block. Next will flush the block and pull the water pump. Broke a bolt on the thermostat housing - may replace the pump after all, and put the OEM in reserve. Will know after I flush the block and remove the pump.


I did spend a luttle time creating a Relationship Diagram of the Causes, Symptoms, Parts, and Responsible Parties. It may be helpful to others. At least if as an operator, you observe some of the Symptoms, you might find some use in identifying the potential problem area - before an overheat!




OOPS - Just noticed! I forgot the Cooling Fan! This is a problem I'll add to a revision on the diagram. It would be on the Owner/Operator side.

There is a challenge with a stock setup - you'll have no way of knowing until you get the overheat indication or CEL, and pull over. You could note the fan not turning - assuming you still have the engine running. With my electric fans, my "Mod" will be 2 small 12v dash LEDs to indicate "Power-On." It won't guarantee the fans are running, but that there is power to them. There is always a possibility the thermostat relay could go out and the fans lose power and stop. They are "spared."

Cheers - Jim