Cat 3126 Motor Runs Hot

lkrompier

Member
Aug 4, 2009
54
New Jersey
Boat Info
2007 44 Sedan Bridge
Engines
Cummins QSC 500 Diesels-478 HP
I have a 2001 400 Sedan Bridge with 3126 Cat Diesels with 630 hours. My port motor has been running hot around 195-200 under load at 2400 rpm cruise and comes right down to 185 at lower speeds. The starboard motor max's out at 185 which is normal. Although you can smell antifreeze, (I think from the engine getting hot) the antifreeze level is good and I can find no leaks (oil is not cloudy either), the strainer is clean, I changed the impellers last week and flushed the heat exchanger with a hose on the intake side and dislodged some rubber from old impeller(s). Could the heat exchanger still be somewhat clogged? It doesn't look like the end of the heat exchanger is designed to come off for proper cleaning with the (6) bolts holding the end cover on. Does it? I have not flushed the after cooler yet. Could it be a thermostat? I'm running out of ideas. Anyone have this problem before or have suggestions on how to bring this temp down to normal? HELP.....

Thanks,

Larry
 
Caterpillar's cooling system has more capacity than the 3126 needs, so your issue is that you have inadequate cooling water flow. Either the intake or plumbing between the intake and the strainer are fouled, or your heat exchanger needs cleaning........most likely the heat exchanger, if they have never been cleaned before.

The end caps do come off and the tube bundle on the inside is removable by sliding it out. The end caps are non-metallic, so be careful with them. Also there are a number of o-rings used to seal the tube bundle and end caps. Don't begin this until you have the replacement o-ring kit in your hand. On some boats, the tube bundle can be removed with the heat exchanger mounted on the engine, but on others, you have to remove the heat exchanger from the boat in order to have room to slide the tube bundle out.

This job is a little more than most owners are up for. It is a lot more than "pop a cap and flush it out". The tube bundle must be acid cleaned and rodded out to clear all the crud and broken zinc parts. You might want to get Caterpillar to clean them the first time so you can watch and see how to go about it in th e future.

Also, do both engines since the other is not far behind. Don't forget the generator.......its probably dirty too.
 
Thanks, Frank. I don't know how clogged the exchanger could be with a boat that's not particularly old. I bought he boat the beginning of last season from Connecticut and the LI Sound and brought it to Toms River, NJ which is brackish water without much "crud " normally accumulating. I don't think the bundle will come out without removing the whole heat exchanger. Reaching the impeller on the outboard side of the port motor was a NIGHTMARE. Four hours for the port motor and I almost got stuck in the engine and I'm an average size guy. Is ther any chance any rubber may have become lodged at the aftercooler and is causing (contributing) to the problem. Can you tell, I'm not anxious to remove the heat exchanger?

Thanks,

Larry
 
Since you apparently don't have the service records for the boat, you can't assume the heat exchanger's been cleaned out recently, if ever. Eight years (if that's the case) would be waaayyy too long. My 3208's are different anyway, but IIRC when the mechanics did mine a few years ago only one end was removeable, with the stbd. engine being the "easy" side like yours. Same problem with the port side impeller a few months ago. Took two mechanics- the "littler" guy lying over top of the engine hanging halfway down into the bilge at the front rt. corner of the engine (I'd never have fit) while the other leaned in and reached around the front of the engine to tighten the bolts. Definitely a two man job on my engine, and it was easier to remove the whole bracket with the pump intact.

I would first confirm with the engine-mounted gauges. My stbd helm gauge reads 8 degrees high compared to the engine mounted gauges. IR temp gun would be even better. You want to be sure you actually have a problem, before you begin chasing ghosts. Then the heat exchanger like Frank said.
 
My Stb engine also runs hotter by 10F but after cleaning the heat exchanger (able to pull bundle in the boat) and replacing the pump impellar.... there was no change. I put a thermocouple on both engines and found the port runs the same temp as the stb engine...so I was chasing a ghost.

I would be concerned if you can smell antifreeze. I also used a product called Rydelyme which descaled my heat exchanger. I pump it thru when I first purchased the boat and the tube sheet came out pretty clean. After two years, I pulled the heat exchanger chasing my ghost. I used the Rydelyme to clean the tube sheet assembly and it was spotless upon re-install.

Good Luck....
 
I also used a product called Rydelyme which descaled my heat exchanger. I pump it thru when I first purchased the boat and the tube sheet came out pretty clean. After two years, I pulled the heat exchanger chasing my ghost. I used the Rydelyme to clean the tube sheet assembly and it was spotless upon re-install.

Good Luck....


+1 I clean mine with rydelyme. I use a sump pump and pass it from the intercoler to the heat exchanger and oil cooler perfect job in less than 30 minute
 
If I run Rydlyme through the system starting at my aftercooler and discharging at the trans oil cooler (which would circulate through the whole cooling system) do I need to bypass the raw water pump (and impeller)? Will Rydlyme damage the rubber impeller?
 
Yes....you need to by pass the pump. I connected a small bildge pump in a 2 gallon bucket using 1/2 or maybe 5/8" poly hose to set up the recirc system. It will not dissolve any pump fragments.
 
I would do the Rydlyme first, especially if the heat exchanger needs to be pulled to get the end cap off to get the bundle out. Rydlyme will dissolve zincs- a good thing (because it will dissolve any chunks that broke off and are clogging your cooling system) and bad -because you have engine zincs. Remove your engine zincs before flushing -just put the brass plugs back in until done-don't forget to put them back in after flushing.
 
I know this is old. My thought is most of you still own a boat and have just had more experience since the original post. :).

Anyone know best discount place to purchase Rydlyme? Amazon is crazy: Price: $29.95 + $17.20 shipping for a gallon. I need to do two CAT 3126s, a generator, and my cooling system. Any idea how much is required for this? is it less effective to "re-use" or should i expect a gallon for each?
 
Frank, is this the stuff you said can be used in place of Rydlyme?
klean-strip-paint-thinner-solvents-cleaners-gkpa30220-64_1000.jpg
 
I used a product called Barnacle Buster from West Marine. I bought the concentrated formula, you add it to 5 gallons of water to get the proper solution. It was pretty spendy, something like $80 for a gallon, but you only need to buy the one. I only did my mains, I didn't flush my genset. I saved the solution, so I could always just run it through the generator later - it's good for multiple uses until the pH reduces too far.
 
Barnacle Buster and the paint stripper above are both phosphoric acid. According to the MSDS, BB is ~50% H3PO4, Klean-Strip is 35-40%.
 
Not sure but take a look at the Material Safety Data Sheet (usually available online) to see the chemical makeup. If it gets rid of lyme it's got to me some sort of acid. Muriatic?
 
I guess you just have to pick your favorite acid!
 
OK, scratch muriatic off your list of favorites ;-)
 

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