CAT 3126 engines flushing raw water side

C

Chris1960

New Member
Mar 3, 2008
42
Isle of Wight UK
Boat Info
Sunseeker Portofino 400
40foot sports boat
Engines
2 x CAT 3126 420hp
My 1996 CAT3126 engines have been running fine all summer with temps both at a steady 80 degrees C (175degrees F). I have noticed that the last few times out the starboard engine temp has crept up to 85 (185 degrees F) and stays there.
With all the stuff I have read on here and other sites about these engines I know that it is important not to overheat them so I am keen to sort this problem before it becomes a major issue.
At the start of this season, I flushed out and replaced the (older CAT) coolant with CAT ELC, which was clean anyway. I have changed the impellor a few weeks back on this engine too but this has not made any difference. The engines were re-built by CAT with new blocks in 2002 at 430 hours and now have 650hours on them.
I am considering using Rydlime to flush through the seawater cooling side of the system. Has anyone done this ? Would anyone advise against and how would I do it. My idea is to take out the zincs and fill up with Rydline through these holes, replace the bolts and leave for a while before starting the engine and allowing seawater to flush out before replacing zincs again. Good plan or not ?
 
I'm sure Frank W. will pipe in with engine specific things but I've used Rydlyme for about 4 years now on my boat as well as things around the house. The stuff is basically a solution of phosphoric acid and some other magic stuff (wetting agents). I've had very good luck with it and when I peak into my heat exchangers, they look brand new.

I don't soak them as you say though but have a flush kit I built with a pump (from Northern Tool) and a 5 gallon bucket. The pump really puts out a lot of volume. I circulate the stuff through for about 2 hours. My bucket sprung a leak from a crack this year so I've got to redo it and will go with a 10 gallon container. The reason is that when the acid reacts with the scale in the system, it foams... and foams a lot and the foam can overflow the bucket.... a lot... Ever put Mentos in Coke?

I've heard of people soaking the engine than just starting it up but the reason I have a high volume flush is I want it to also flush out the sand, dirt, and other small particle debris. Rydlyme does not dissolve that stuff so the several hours of flushing action with a high volume pump has done a good job for me. I still pull the entrance of the raw water system into the first heat exchanger (the aftercooler in my case) and make sure there are no larger items like impeller parts, grass, tampons, etc.

I will say if you have a complete blockage I'm not sure how well this stuff will work. You may have to get the things rodded out. I use it more in a preventative sense and it works very well. Also, at some point, the aftercooler on the air side has to be cleaned and this doesn't do that. Additionally, getting heat exchangers pressure tested from time-to-time is a good idea and I do see your boat is over 10 years old.... I'm not sure what your growth/scale issues are like in the UK, but in the mid-atlantic area of the US if you dangle your feet in the water more than 30 minutes, you'll have growth on them.

One last note... make sure you flush with fresh water well afterwards. I actually add a little baking soda to the last fresh water flush and then go run the engines. You don't want acid hanging around inside your cooling system for any length of time... especially if you have any aluminum parts. Copper/bronze + Aluminum + Acid = very good battery.

This stuff also works great with the AC systems on the boat.
 
Last edited:
If you have gone from 1996 to now without cleaning your heat exchangers, then you should remove the interior tube bundles and clean then with acid. You will also need to rod the individual tubes to get the crusty debris loose and gone. Gary's method is a good one for regular cleanings, but I doubt you will have much success with Rydlyme if your heat exchangers have never been cleaned.

Caterpillar significantly over specifies cooling system capacity so it is normal that you can run for several years with no cooling system maintenance. However, you have the beginning symptoms of a dirty heat exchanger if you temps are beginning to rise. These engines run with a 194 degree thermostat, so you are still passing enough water thru your engines to cool properly if all you are seeing is 184 degrees.

Lastly, depending upon what boat and transmission you have, your transmission oil cooler is just down stream of your main heat exchanger. All the water exiting the heat exchanger must pass thru the oil cooler before it is expelled. If the oil cooler gets fouled, it will cause the same symptoms. The tubes in the oil cooler are smaller and much easier to clog up than those in the heat exchanger. IF you have transmission oil cooelrs, try removing the inlet hose and just looking inside. You can easily see how much fouling you have. The oil coolers are easy to remove and clean off the boat, so that may be a starting place for you.
 
Chris1960 said:
My idea is to take out the zincs and fill up with Rydline through these holes, replace the bolts and leave for a while before starting the engine and allowing seawater to flush out before replacing zincs again. Good plan or not ?
Click to expand...

You need to create a "loop"- read this:

http://www.rydlymemarine.com/pdfs/MARINE ENGINE RAW.pdf

Rydlyme eats the zincs, mine needed replacing anyway so I left them in and replaced after flushing. Otherwise take them out beforehand.
 
Thanks Gary, Frank and Tobnpr for your very useful info, I just want to say that this forum is great for information on these engines as CAT are not very popular here in the UK and you guys have always been so helpful

I think I will do as Frank says, I have the engines mounted backwards through a ZF gearbox and I do have the transmission oil coolers. So I will start here and see if that helps to reduce temps, then move on to the heat exchanger if neccessary

Is getting the transmission oil cooler off an easy job and is there anything else I need to do. Is it just a simple thing of undoing the oil connections and undoing the raw water connections are there any seals or O rings I need to buy first.

I have only had this boat coming up to a year so I do not know a great deal about its history I also have some discoulouring of the aftercooler on this engine (see pic here: http://www.photobox.co.uk/my/photo?album_id=28984505&photo_id=1678140849) and I recently stuck a label on it with the date of coolant change (coz I now find that if I dont write it down asap, its forgotten !) and that seems to have bubbled up with the heat. Is this something else to be wary of ? Sorry to slip another question in there
 
The transmission oil cooler has 2 hydraulic lines that will leak oil when disconnected, so be prepared to tie them in an elevated position when you break them loose. You will also need rags to place under the oil cooler since it is full of transmission oil.

The inlet and outlet hoses need to come off, and last, there are 2 bolts holding the oil cooler to then bell housing that must be removed. Take the zincs out while the oil cooler is still attached to the engine....its much easier.

The aftercoolers do run hot on these engines, but they should not be hot enough to burn off paint. Was your boat new? There is a known problem with 3116 and 3126 engines (no other Cat engines, just these 2) that have been run a few hundred hours with multiviscosity oil in them. I don't know why, but the viscosity enhancers in the oil additive package breaks down and fouls the aftercooler. The only fix it to remove and have them cleaned. You can read about oil requirements on the Cat.com site under fluids, but generally you should be using either Caterpillar SAEO 30 or 40 wt (part #'s 170-5261 or 2 depending upon viscosity) or a high quality diesel oil like Rotella T or Delo 400 in SAE 30 or SAE 40 single viscosity oil. Do not use multiviscosity oils (like 15W40).

Finally, find a Caterpillar parts source and buy extra hoses for both ends......small with almost 90 degree beds of the transmission oil coolers....... and an extra for the water pump to heat exchanger hose. All of these hoses have full pump pressure on them and if you have a hose fail, it is going to be one of these 3.
 
Hi Frank

Boat & engines are from 1996 & always maintained by CAT in UK. In 1999 under warranty CAT did new inlet and exhaust valves, modified turbo assy, modified jacket water pump and new exhaust manifold including studs.
in 2002 engines had new blocks + other stuff under CAT recall done by CAT Marine power here in UK.
Boat was out of the water for 18months before I bought it as owner has 5 other boats inc 2 in florida (so I am told) he lost interest in this one when he bought a new 50footer ! I wish I had that sort of money, imagine the mooring fees !!!

I changed oils in Jan this year and used Shell X30 (after seeing other posts on here) which is the same as your Rotella Monograde 30 and there were half used containers of CAT SAE30 on the boat so I am sure the correct oil has been used in the past.

I never noticed this discolouring at the time of the pre-purchase survey Dec 2007 as the whole floor of the boat has to come up (which I didnt do) to gain reasonable access. Access is normally through a small hatch and its normally dark down there

I will buy some spares like you say as they are bound to break esp when I take them off

My list of stuff to do on the boat this winter is rapidly growing. I bought some LED lights to light up the stair treads into the cabin at the big Southampton boat show we have here in the UK and this is the job I'm looking forward to most
 
Hello, this is my first posting! I am the proud owner of a 40 Foot Sedan Bridge with 3126 Cats, 1998, 995 hours. Here is my saga with some thoughts on temperatures.

Purchased boat from a friend last year that was fighting temp. issue (concern) when I purchased, Cat dealers were telling us both to run around 195 degrees is not a big deal, they indicate call when it hits 200. My research showed that the engines have 180 thermo-stats and the port engine always ran right at 180, the stbd ran at 195, so my thinking was there is a problem.
The following items were done to bring the engine back to temperature, clean and acid treated the suction screens that are mounted on through hulls, they were about 50% clogged, not to be confused with the strainers, paint and sea stuff over the years. Changed the impeller and tighten the belts, treated sea water side with muracitic (spelling?) acid, removed numeruous zinc pencils restricting flow. Temperature went to 185, still not as good as port. I always perform items to both engines, low cost basic maintenance.
Pretty frustrated now, why the tempertaure is still higher, checked anti-freeze level, stbd was at -50, way to low, even for a boat in Boston, drain and added water(-10), immediate change, both temps. running the same, hold on, not for long. After a couple of trips temp comes all the way back to 195 for stbd, port remains at 180. More research and discussions with my yard mechanic, he mentions check the silt level in your cooliing system, say what, stick your finger in the coolant cap resevior area and see what you have, rub your finger around the surface. Sure enough I came back with a black slit, almost like an oil slick ( on my finger) on the surface of the cooling system. Off to the CAT store and come back with engine flush, drain the coolant, add fresh water and the chemcial, ran engines for about 2 hours under load, back to the dock to drain and flush with water. Black water like you have never seen came from both engines, pretty tough smell as well. Changed thermo-stat on Stbd, port was done the year before by previous owner, stbd came to 180, bad news, the port now runs at 175, this is just not fair. So, drive the boat some more and here we go again, stbd starts to creep back again, 185 and port is killing me at 175, still have the 10 degree spread. Please keep in mind this is over the boating season of 2008, a period of 3-4 months of running. Near the end of the season I employ the mechanic to come down and have a look, I complained to him at 2000 rpm the temp on stbd runs at 185, push the boat to 2250 and the temp comes down, yes Santa we have a flow problem now. He suggests that we replace the cam plate on the sea water pump, this must be it! He does this and tightens the belts again, we both worked on the belts at the start of the season. he is about half my size.

Now I ask him to come for a ride and bring along his infra red temp sensor tool and we take off, port runs at 175-178, stbd runs at 180, the sage appears to be over, I hope. For fun he runs to the engine room and takes temps on both engines and comes back to the bridge with the news, in all cases the port engine was running slightly warmer than the stbd, even with the gages reading different. A couple of people told me to switch the wiring on the sender to check this out, ran out of time this season. I can live with a 5-7 degree spread, can clearly call that calibration error, any thing more sends me to the engine room. I don't think the senders cost much, perghaps something to do next year!

In the end, cooling is big, keeps bad luck at bay!

Thanks,
Pat
 
Pat, FrankW will chime in soon but I think you might be fighting a "Ghost". Glad you got it where you want it but your old numbers where not that bad IMHO. Keep us posted. JC
 
This one is going to be hard to fix because it may not be broken........

These engines are supposed to have a 194 degree thermostat in them and they should run that temp. I can't get excited about a pair of engines running 175-185 degrees. Cat significantly over engineers their cooling systems so it takes a pretty good problem to get them hot (over 200 degrees). Most frequently, reduced water flow causes the overheart, but since your engines are not overheating I wouldn't know where to begin trouble shooting.

One factor to consider is that the cooling system has 2 sides.....the sea water side that can get marine growth in it and the antifreeze side that can get silicate deposits from old antifeeze. Be sure you use only Cat ELC coolant and change it at least every 5 years. You can use an extender, but no more expensive than the ELC is, I just change the coolant.

Another possible cause for the different temps side to side is the fact that the water heater's heat exchanger ads cooling capacity to one side or the other........I don't know which on the 400DB. The side feeding the water heater will run some cooler than the opposite side whis has several gallons less coolant capacity.
 
Frank,
Thanks for the note back, this issue I had was the 180 versus the 195 earlier in the season. This is the first I heard about the 194 thermostat, I went directly to CAT and they pulled the 180 off the shelf.

I did clean both sides as indicated, I suspect that my problem is over, just thought people would be interested in my saga.

Happy Holidays!

Pat
 
fwebster said:
If you have gone from 1996 to now without cleaning your heat exchangers, then you should remove the interior tube bundles and clean then with acid. You will also need to rod the individual tubes to get the crusty debris loose and gone. Gary's method is a good one for regular cleanings, but I doubt you will have much success with Rydlyme if your heat exchangers have never been cleaned.

Caterpillar significantly over specifies cooling system capacity so it is normal that you can run for several years with no cooling system maintenance. However, you have the beginning symptoms of a dirty heat exchanger if you temps are beginning to rise. These engines run with a 194 degree thermostat, so you are still passing enough water thru your engines to cool properly if all you are seeing is 184 degrees.

Lastly, depending upon what boat and transmission you have, your transmission oil cooler is just down stream of your main heat exchanger. All the water exiting the heat exchanger must pass thru the oil cooler before it is expelled. If the oil cooler gets fouled, it will cause the same symptoms. The tubes in the oil cooler are smaller and much easier to clog up than those in the heat exchanger. IF you have transmission oil cooelrs, try removing the inlet hose and just looking inside. You can easily see how much fouling you have. The oil coolers are easy to remove and clean off the boat, so that may be a starting place for you.
Click to expand...
Frank,
How do you clean your coolers off the boat. Specifically what do you use. Do you cap the oil lines and soak them in a bucket of ?????.
Jack
 
I take it you mean the oil coolers?

This is really pretty much like cleaning a radiator........you remove the hydraulic lines and plug the inlet and outlet. I used plastic caps and duck tape. If you don't cap them on the boat you will make one heck of a mess getting them out of the engine room. Next remove the water lines, any senders and mounting bolts and take the coolers off the boat. Look inside and remove anything that is loose like grass or hunks of old annodes. I used phosphoric acid and a brass (brazing) rod that will fit into the tubes inside the cooler. Cleaning is a combination of mechanical and chemical methods, i.e. punching solids out of the tubes and allowing the acid to dissolve the crud around the tube openings. I ended up using muriatic acid for some of the hard spots, but be careful, muriatic acid can errode the solder used in assembling the cooler. When they are clean, flush with a baking soda solution to neutralize the acid, rinse in fresh water and put 'em back on the boat. If you have allowed water or acid to enter the oil side of the cooler, then flush it with new transmission oil or fluid.

There, all done........!
 
fwebster said:
I take it you mean the oil coolers?

This is really pretty much like cleaning a radiator........you remove the hydraulic lines and plug the inlet and outlet. I used plastic caps and duck tape. If you don't cap them on the boat you will make one heck of a mess getting them out of the engine room. Next remove the water lines, any senders and mounting bolts and take the coolers off the boat. Look inside and remove anything that is loose like grass or hunks of old annodes. I used phosphoric acid and a brass (brazing) rod that will fit into the tubes inside the cooler. Cleaning is a combination of mechanical and chemical methods, i.e. punching solids out of the tubes and allowing the acid to dissolve the crud around the tube openings. I ended up using muriatic acid for some of the hard spots, but be careful, muriatic acid can errode the solder used in assembling the cooler. When they are clean, flush with a baking soda solution to neutralize the acid, rinse in fresh water and put 'em back on the boat. If you have allowed water or acid to enter the oil side of the cooler, then flush it with new transmission oil or fluid.

There, all done........!
Click to expand...

I took mine out and straight to local "old school" radiator shop and they hot tanked them... Cleaned them out, as good as new, then primed them, I put a coat of CAT white on them and then back into the boat....
 
This is an old thread so hope someone sees this post and responds. I am learning about my 3126's after years of dealing with I/O gas engines. We are about to pull the boat and leave it on the hard for several months and figure I need to get salt water out of the raw water side. I don't understand about the flushing / pumping / circulating previous posts. To flush my gas generators I would just run the hose with salt inhibitor mixer attached into the strainer housing and let it suck it through. To winterize, same thing but with the water antifreeze pink stuff. I was thinking about doing the same thing for the 3126's. In other words, close sea cocks, pull out the strainer baskets, run the salt inhibitor mix into the strainer and start the engine. Is this stupid? If it is please advise right way to leave these guys unattended after use in salt water. Thanks.
 
roger275 said:
This is an old thread so hope someone sees this post and responds. I am learning about my 3126's after years of dealing with I/O gas engines. We are about to pull the boat and leave it on the hard for several months and figure I need to get salt water out of the raw water side. I don't understand about the flushing / pumping / circulating previous posts. To flush my gas generators I would just run the hose with salt inhibitor mixer attached into the strainer housing and let it suck it through. To winterize, same thing but with the water antifreeze pink stuff. I was thinking about doing the same thing for the 3126's. In other words, close sea cocks, pull out the strainer baskets, run the salt inhibitor mix into the strainer and start the engine. Is this stupid? If it is please advise right way to leave these guys unattended after use in salt water. Thanks.
Click to expand...


That sounds a bit risky to me. I personally would not start my engines with seacocks closed and just the liquid in the strainer to do the job. I am in fresh water so that is not a concern but would be interested in how best to do this just for flushing. I do remember a thread where Gary (Four Suns) had set up a method for flushing I believe. After reading this thread, I do need to inspect my oil coolers as that is the only piece of my cooling system I have not serviced yet.
 
fwebster said:
I take it you mean the oil coolers?

This is really pretty much like cleaning a radiator........you remove the hydraulic lines and plug the inlet and outlet. I used plastic caps and duck tape. If you don't cap them on the boat you will make one heck of a mess getting them out of the engine room. Next remove the water lines, any senders and mounting bolts and take the coolers off the boat. Look inside and remove anything that is loose like grass or hunks of old annodes. I used phosphoric acid and a brass (brazing) rod that will fit into the tubes inside the cooler. Cleaning is a combination of mechanical and chemical methods, i.e. punching solids out of the tubes and allowing the acid to dissolve the crud around the tube openings. I ended up using muriatic acid for some of the hard spots, but be careful, muriatic acid can errode the solder used in assembling the cooler. When they are clean, flush with a baking soda solution to neutralize the acid, rinse in fresh water and put 'em back on the boat. If you have allowed water or acid to enter the oil side of the cooler, then flush it with new transmission oil or fluid.

There, all done........!
Click to expand...
"brass (brazing) rod that will fit into the tubes inside the cooler."

Yes I know, a very old thread...what size/diameter rods so I can purchase these before I go to the boat?


Thanks
 
You must log in or register to reply here.

Forum statistics

Threads
113,238
Messages
1,429,070
Members
61,119
Latest member
KenBoat
Back
Top