Cummins engine questions

[Baker]

Before I deal with this heating issue further I will do as David and others suggested - calibrate the gauge with an IR gun. I cleaned both after coolers yesterday and they will be re-installed later this week and I'll post the results.

That's interesting John and I'll bet most of us have never heard of that. On my port engine BEFORE it was replaced with the reman, I had to remove some coolant for some procedure I've since forgot and to replace the lost coolant I went to Walmart and picked up some I believe Prestone. When I got back to the boat and opened the container it was orange in color, not like the green color coolant that was in the engine. I called Tony and he said it was OK to use.

The orange color coolant looks too much like diesel fuel on oil absorbing rags and makes it difficult to diagnose leaks. I don't know how to tell the color of a bottle of coolant without opening it first.

Cummins explanation:
https://www.cumminsfiltration.com/pdfs/product_lit/emea_brochures/LI33024-GB.pdf

 

[High Wire]

Before running down this rabbit hole you want to verify the tachs are still reading correctly with a strobe tach.
If these are analog temp gauges there are plenty of things that will cause a variation of a reading. Just a slight change of resistance in the connections of the harness wiring could cause what you are seeing. Here's what I would do to check the gauges. Since you need to compare Granny Smith apples to Granny Smith apples, do everything identical on each engine. Always WRITE DOWN all results.

1) Engine not running. Disconnect the lead at the temp sender. Put a 47 ohm resistor between the harness lead and block ground with short length test leads. Read the gauge as accurately as you can. Write the value down. Repeat on the other engine. Next, add a second 47 ohm resistor in parallel to the first. This will move the gauge needle higher or lower on the scale for a second reference point. Record readings for both engines. If they read the same, great and move to #2. If not, start cleaning connections.

2) Swap senders. The temp senders should not have thread sealant on them. That will affect the resistance seen by the gauges. You can measure ohms between the hex head of the sender and a good clean engine block ground should be < 1 ohm. Run the boat as before. Did the problem move to the other engine?

If you still believe its a gauge problem...

3) Engine running. NEED TO BE VERY CAREFUL to not get anything caught in moving belts!!! Disconnect temp sender and measure resistance of senders with a digital VOM. While the engine is warming up (depending on the gauge manufacturer) the resistance will rise or fall as temp rises. These readings will be a moving target so a second person will help. Record IR temp and ohm readings every 10 degrees. Compare engine data. Do the ohms readings agree?

 

[ranger58sb]

Flushing your cooling system with ridlyme is not a definitive way to clean your coolers. Any picture of a clogged cooler will explain why.

Yep, I know it's not the real thing. Just was easy to do as a sorta-kinda a preventive measure in a raw water system that seems to be operating at spec.It was an easy way to get to the fuel cooler, transmission oil cooler, raw water side of the aftercooler, etc. all at once. Buying some time 'til the real deal becomes necessary. (Aftercoolers due for real service in early March.)

-Chris

 

[ranger58sb]

There are two things that inhibit heat transfer in a heat exchanger. The classic gunk that an acid wash can cure(rust,scale/lyme,etc). But there is also the silcate gel that acid or ridlyme will do nothing to help. Silicate gel is usually caused by using incompatible coolants so probably not an issue in this case. But I have heard the symptom is a gradual increase in temp. Anyway, Fleetguard sells Restore which is good on the classic stuff and there is Restore Plus used primarily for the removal of silicate gel. My guy says that the only way to remove silicate gel is ultrasonic/laser treatment by some specialist in our area. But dunno who to believe. My point here is there are two very different things that can retard heat transfer meaning there is no one universal solution to flush with.

We just replaced our antifreeze in November (came time, on the maintenance schedule), and during the process we also flushed the cooling systems with Restore. But that's on the freshwater side, not the raw water side...

So what you're describing would be about silicate inhibiting the flow of hot antifreeze through the heat exchanger tubes, yes?

-Chris

 

[Baker]

We just replaced our antifreeze in November (came time, on the maintenance schedule), and during the process we also flushed the cooling systems with Restore. But that's on the freshwater side, not the raw water side...

So what you're describing would be about silicate inhibiting the flow of hot antifreeze through the heat exchanger tubes, yes?

-Chris

It is not inhibiting flow. It inhibits heat transfer on the freshwater side. . I have heard that a HX fouled by silicate gel is slightly discolored. It does not clog the cooler in any way. It is simply a thin film that prevents heat transfer. Did you use Restore on the raw water side? That is not what it is made for.

 

[ranger58sb]

It is not inhibiting flow. It inhibits heat transfer on the freshwater side. . I have heard that a HX fouled by silicate gel is slightly discolored. It does not clog the cooler in any way. It is simply a thin film that prevents heat transfer. Did you use Restore on the raw water side? That is not what it is made for.

No, it was Restore in the freshwater (antifreeze) side.

The silicate accumulates on the insides of the whole freshwater system, yes? Not just the HX? So maybe inside the HX is the only place it impedes heat transfer?

-Chris

 

[smitty477]

Other ways to check for silicate mud buildup would include looking at the bottoms of the overflow bottles if you have them. Also - sometimes you can reach into the top of the radiator cap (engine off and cold) and 'wipe' the top of the cooling bundle with a finger. If you do this while using a bright flashlight you may see some 'mud' removed from where your finger wiped it - that is silicate and it forms quite an impressive insulator.
The silicate will drop out of suspension mostly where it is cooled from normal operating temps - that would be right where the cooling bundles are located.

 

[Baker]

The silicate accumulates on the insides of the whole freshwater system, yes? Not just the HX? So maybe inside the HX is the only place it impedes heat transfer?

-Chris

I think you are getting hung up on the "accumulation". It does not inhibit flow and if it does "accumulate" in other parts of the system, it does no harm... in theory. The inside of the HX is the place where heat transfer takes place. It is THE PURPOSE of the HX(hence the term "exchanger") and if heat is not "exchanging", we have an issue.

I think what smitty is saying is that it is in solution when things are hot...and then it cooks onto the HX surfaces as it cool. And you keep putting layer after layer of this stuff onto the walls of the HX. This is a micro thin coating.

 

[ranger58sb]

I'm getting it, thanks. Already understood the whole heat exchanger part; just trying to be sure I know where exactly the silicate is living when it's doing the dirty.


And thanks also for bringing it up in the first place. I can easily (usually) follow recommendations in the Cummins service manual (e.g., "use Restore periodically) but it helps to know more details about the why.


-Chris

 

[ranger58sb]

Flushing your cooling system with ridlyme is not a definitive way to clean your coolers. Any picture of a clogged cooler will explain why.

Yep, I know it's not the real thing. Just was easy to do as a sorta-kinda a preventive measure in a raw water system that seems to be operating at spec.It was an easy way to get to the fuel cooler, transmission oil cooler, raw water side of the aftercooler, etc. all at once. Buying some time 'til the real deal becomes necessary. (Aftercoolers due for real service in early March.)

I should have added, I flushed the genset HX with Rydlyme at the same time, and in this case I actually did take before/after photos. The Rydlyme did a very good job of cleaning the raw water side. Lots of gunk visible before, no visible gunk afterwards.

Then later, when we used flushed the mains with Restore and replaced the antifreeze with new... we did all that on the genset freshwater side, too.

Probably still not the same as removing and taking it to a shop, but much easier for me to do.

-Chris

 

[Nomad Willy]

Many boats
I don't think Cummins is in any financial difficulty. They have a strong balance sheet. Engine sales to truck manufacturers have dropped a bit; US sales have been strong until very recently. Sales to China and Brazil are way down, no surprise given their economies. Can't give you a break down on marine sales.
Now the stock, which reached about 160, has dropped to about 85; a reflection of concerns that US sales may have stalled and foreign sales remain poor. It trades at about a 9 P/E.

Well a stock going down that much would seem like trouble to me. But as a pleasure boat owner wanting to have Cummins products available as before this may not be bad berries. If it was others would probably be talk'in about it and they aren't. Thanks for the reassuring info.

 

[bnoft]

unfortunately, there are a lot of stocks down 20-35%, granted CMI is off more like 45%, both are painful

 

[FF]

The world is so awash in debt that many businesses world wide are attempting to play Keep Alive , rather than expanding.

This brings down CAT , Cummins , DD, JD and other construction enableing businesses.

 

[bayview]

If you have never opened the heat exchangers on your Cummins it is a good thing to do. Mechanics sometimes don't bother getting the old zinc residue out when servicing the system. My boat was only a couple of years old when I got it but I found several zinc stubs blocking the sendure HEs.