CAT HEUI issues, failures and fixes

[87cr250r]

It is my understanding that a thinner oil will help prevent shoe lift.

 

[MatthewWBailey]

It is my understanding that a thinner oil will help prevent shoe lift.

Would synthetic have any impact?

 

[GeneralDisorder]

Would synthetic have any impact?

Synthetic tends to have better cold flow characteristics. I run Amsoil 15w40. 5k changes. 25k miles and zero issues but I'm running a C7.

I have run into several references to 3126B applications (RV's for example) calling for 10w30...... Perhaps this was in part for the HEUI pump? No clue if that's related.

Also synthetics get thinner over time - the long molecule chains and viscosity modifiers get chopped up due to shearing forces, and the synthetic base doesn't sludge or varnish to act as a thickener. In some engines, fuel dilution can further act to thin the oil over time. In the FMTV application the cooling system is particularly large and these trucks have a hard time getting up to operating temp to drive off moisture and fuel dilution. Care should be taken to get the engine up to full operating temp periodically (as often as possible).

 

[MatthewWBailey]

Synthetic tends to have better cold flow characteristics. I run Amsoil 15w40. 5k changes. 25k miles and zero issues but I'm running a C7.

I have run into several references to 3126B applications (RV's for example) calling for 10w30...... Perhaps this was in part for the HEUI pump? No clue if that's related.

Also synthetics get thinner over time - the long molecule chains and viscosity modifiers get chopped up due to shearing forces, and the synthetic base doesn't sludge or varnish to act as a thickener. In some engines, fuel dilution can further act to thin the oil over time. In the FMTV application the cooling system is particularly large and these trucks have a hard time getting up to operating temp to drive off moisture and fuel dilution. Care should be taken to get the engine up to full operating temp periodically (as often as possible).

Im Coming up on 5k with Amsoil 15w-40 synthetic. Any benefit to going down to the 10w-40?

 

[GeneralDisorder]

Probably isn't going to make any significant difference. A block heater and oil pan heater will accomplish a lot more.

Wider range of multi-viscosity ratings indicates larger quantities of viscosity modifiers.... These are molecules that coil up like a spring (or uncoil) when their temperature changes. This is how they change the viscosity characteristics. How those "additives" effect the lubrication properties of the underlying oil or it's life span is only going to be determined by analysis.

I would like to understand when and what applications CAT recommended 10w30 for in the 3126 (if any, officially) and what the motivation for that recommendation was..... Was it a fuel economy driven choice or was it an attempt to mitigate an issue with the early HEUI pump? I know there are thinner oils that can be used in really cold Arctic conditions - not taking about that. I'm taking about a factory recommended 10w30 fill for normal ambient conditions on a 3126B.

FWIW, the Amsoil signature 0w20 out performs all their other oils in terms of wear and film strength. Likely too thin for our clearances and pumps. Newer engines built for it however......

 

[Skyhawk13205]

Im Coming up on 5k with Amsoil 15w-40 synthetic. Any benefit to going down to the 10w-40?

Reading through the recommendations is that you should use the highest viscosity for your temp range

CAT seems to think 10W-30 is what is best for my temp range up here in Alaska, 15w-40 is just so common and significantly cheaper than trying to find a different grade. My truck has been run with 15w-40 for its whole life and the HEUI pump is still operational.



Over sized cooling system seems to be a problem here, I try really hard to get the cooling fan to cycle, with ECO hubs it almost never happens. I am planning on leaving the radiator cover on for the summer to see if I can get my engine up to temp. The engine always sits at 185 deg which is what the thermostat is regulated at.

 

[GeneralDisorder]

Interesting.

If you want to get the fan cycling just hit the high idle button, leave the exhaust brake in warmup and walk away for an hour. Come back and flip the exhaust brake off and let it run at high idle as long as you like. The Army does this often weekly. Motorpool Mondays - start every truck in the morning and let them run on high idle all day.....

 

[Skyhawk13205]

Interesting.

If you want to get the fan cycling just hit the high idle button, leave the exhaust brake in warmup and walk away for an hour. Come back and flip the exhaust brake off and let it run at high idle as long as you like. The Army does this often weekly. Motorpool Mondays - start every truck in the morning and let them run on high idle all day.....

when I run the PTO or have the TC stalled the fan does cycle, but I am assuming that is from the tranmission producing heat.

When I had the geared hubs the fan cycled quite a bit. Also my fan did cycle when my exhaust brake got stuck closed and I was driving on the highway. The temp needle moved so fast I thought the cooling system failed.

 

[Ronmar]

Well if the trans is doing work, the engine is burning fuel and making heat to accomplish that work(And the trans is probably making some also if you are driving around and the thermostat is regulating to 185, then thats where it should be unless you don’t have enough airflow to dissipate the heat. I prefer 195 myself for diesels