CAT 3126s overheating/running hot after sucking up mud

mrsrobinson

Well-Known Member
Mar 9, 2006
7,704
Virginia
Boat Info
2001 380DA
Engines
Caterpillar 3126
New thread to continue the conversation currently on the 3126/3116 thread.

  1. Boat ran strong, 180 degrees both engine first 12 hours post purchase
  2. Sucked up mud entering new creek/marina, both engines overheated, alarm came on
  3. Sea strainers were packed with mud, cleaned them and back flushed seacocks, ran engines at the slip, 160 - 170 degrees
  4. As part of service I was planning to do anyway: replaced all fuel filters, belts, starboard engine fuel primer pump and did the valve lash adjustment. Did not have the tool to set the injector height so that is on the to do list. Took boat out same day for test run. Engines ran at 180 degrees until on plane at 2000 +- RPMs, temps immediately spiked to 200+
  5. Replaced raw water impellers. No broken fins found. Removed end caps on heat exchangers. Looked mostly clean/good to me.
  6. I pulled the inside one off of both engines. I found very very small pieces of an old impeller in one, the port side. This could not be from the impeller I replaced in my opinion since none of the fins were damaged. I removed these pieces and then flushed with dock water, nothing came out/back. I unsuccessfully tried to remove the other end caps so water could move all the way thru. I could not figure out how to get to the last of the 5 bolts with the wrenches/sockets I had. That was next on my list as well.
    I purchased the .22 caliber cleaning rods to do this though I did not since I thought pushing the rod into a hole with other cap on would do more harm than good. Took the boat back out, same result.
  7. Mechanic started to flush the raw water side of port engine with barnacle buster, marina asked him to leave. Started engine 3 hours later to remove the barnacle buster.
  8. Removed, cleaned and reinstalled trans coolers on both engines. Replaced zincs. Looked mostly clean/good to me. Took the boat back out, same result.
  9. Flushed port engine aftercooler with barnacle buster (see video above) since this is the one the mechanic started with. Nothing looked bad to me in the flush. Too much grassy crap in the water so I did not start the engine to go out for a test.
  10. Ordered new raw water pump backing plates and various hoses from Carter Machinery this weekend. I recall seeing some minor grooves on the back of the plates when I changed the impellers, I do not what's acceptable, what's not, so I figured go ahead and replace them.
  11. My next step is to barnacle buster the port heat exchanger.
As I removed hoses/parts I back flushed with the dock hose/spray nozzle. The dock has amazing water pressure. I have not seen any signs of mud or blockage.
 
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I can't get the coolant side of the engine out of my head. You asked about pressure testing the raw water side and I think that makes sense but I would love to see if you could somehow measure coolant flow through the block/passages.

I know the weak point of the coolant side on these engines is the belt driven water pump. I wonder if the overheat somehow knocked the impeller/bearings/pump out and you're getting poor coolant flow or otherwise cavitation and not moving enogh ELC through

Interested to see how the real experts weigh in....
 
Not trying to be picky maybe some clarification on #5 would help the cause -

Did you remove all 4 end caps and inspect them that way, maybe by using a light?
 
I can't get the coolant side of the engine out of my head. You asked about pressure testing the raw water side and I think that makes sense but I would love to see if you could somehow measure coolant flow through the block/passages.

I know the weak point of the coolant side on these engines is the belt driven water pump. I wonder if the overheat somehow knocked the impeller/bearings/pump out and you're getting poor coolant flow or otherwise cavitation and not moving enogh ELC through

Interested to see how the real experts weigh in....
The starboard engine expansion tank cap has leaked since I purchased the boat. A very small leak. The expansion tank on that engine has a dent in it as well. I can see coolant on the underside of the tank as well as at the cap. I ordered a new cap from CAT, and replaced it during step 4 above. I don't think it's leaking anymore, although I still see coolant on the underside of the tank so perhaps it is and it drips down from the top.

I don't think this is related to the over heating as it was this way prior to sucking up mud; but who knows.

The mechanic who got kicked out of the marina suggested checking the temp gauge on top of the engines, as well as using a heat laser gun, to check for true temp, versus trusting the helm gauges. I get this, but the helm gauge temps have changed since the mud event. Also, I have been on the boat alone since then so I can't jump down into the engine compartment while on plane. I did purchase some ear muffs to do this while under power when I have someone on the boat with me. I thought about using the auto pilot; it's a busy river though so that worries me.
 
Not trying to be picky maybe some clarification on #5 would help the cause -

Did you remove all 4 end caps and inspect them that way, maybe by using a light?
I pulled the inside one off of both engines. I found very very small pieces of an old impeller in one, the port side. This could not be from the impeller I replaced in my opinion since none of the fins were damaged. I removed these pieces and then flushed with dock water. I unsuccessfully tried to remove the other end caps so water and light could move all the way thru. I could not figure out how to get to the last of the 5 bolts out with the wrenches/sockets I had. That was next on my list as well.

I purchased the .22 caliber cleaning rods to do this though I did not since I thought pushing the rod into a hole with the other cap on would do more harm than good.
 
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Not trying to be picky maybe some clarification on #5 would help the cause -

Did you remove all 4 end caps and inspect them that way, maybe by using a light?
=====================================

If we establish a pool and take bets on this, I'd be putting my chips on the HEX and the aftercooler

RWS
 
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=====================================

If we establish a pool and take bets on this, I'd be potting my chips on this marker and the aftercooler

RWS
BTW, I did use a led light when inspecting the trans coolers since they were removed and I could see thru them.
 
I have called every radiator and marine shop in the area to ask them if I remove the aftercoolers and heat exchangers can they flush them for me. Most said no, they not want the work. When I questioned the ones who said yes "how" they basically said soap and water and soak it overnight in a tub. One said he'd use Simple Green. I was not impressed.

I was thinking about doing this on my own:

 
You may find impeller pieces in the after-cooler. When I removed mine to be the tanked I found a number of pieces in one of the hose connection and fished them out with fingers and some picks. I was surprised I wasn’t over temperature as a result, but as others have said the system is fairly effiecient. My guess is mud in the heat exchanger. If your down to one bolt, get er’done!
 
If your down to one bolt, get er’done!

Ha, easier said then done. On the port engine at first\second glance I was going to have to remove the expansion tank, hoses, friends and such, which meant draining the coolant; just to get to the last bolt, and I have some pretty nifty wrenches. My GFs cat mechanic brother-in-law had some nifty ones too and he was stumped.

I will take another look.
 
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If you found mud in your strainers but you're not finding mud much further upstream in either engine and yet both are still overheating, I think your problem is from the water pump back towards the seacock.

Can you run a snake through the hoses from the pump to the strainer? How about from the pump to the seacock and out the bottom of the boat?
 
I don't think it's leaking anymore, although I still see coolant on the underside of the tank so perhaps it is and it drips down from the top.

My port expansion tank had a pin-sized hole in it and would only leak once the coolant was up to temp... It took me a few times trying to figure out where the darn leak was. I pulled the tank and off it went to the radiator shop.
 
If you found mud in your strainers but you're not finding mud much further upstream in either engine and yet both are still overheating, I think your problem is from the water pump back towards the seacock.

Can you run a snake through the hoses from the pump to the strainer? How about from the pump to the seacock and out the bottom of the boat?
Agreed, good suggestion. I did back flush it with the high pressure hose at the dock and got good/unrestricted flow. Maybe a stiff piece of wire at this point. Or, a camera/scope of some kind?

https://www.amazon.com/Compatible-N...9Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

Dock mate referred me to a CAT mechanic who just called me. Like the GFs brother-in-law he does not have marine raw water experience. His first thought was the fresh water pumps. He said they can get shaft play at load that they do not get at idle. I think someone here said that as well. He referred me to a Radiator shop they send all of their work to who should be able to dip/clean/pressure test my heat exchangers/coolers. He's not sure about marina application though.

Gawd, I don't even want to think about replacing those, after how challenging it was to replace the belts.
 
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I pulled the Heat exchangers and that included pulling the expansion tanks and replacing all the hoses and sealing rings while in there. I dipped the tube bundles myself with barnacle buster, which is the easy part. I also took the opportunity to have the HEX body powder coated, and replaced the ELC. CAT recommends new radiator caps every so often (but forget the interval).

It’s a very tight area to be working, and I spent WAY TOO much time bilge diving for dropped tools/bolts and nuts.

http://clubsearay.com/index.php?threads/cat-3126-hex.91223/
 
Whoops! Looks like you found that thread already!
 
New thread to continue the conversation currently on the 3126/3116 thread.

  1. Boat ran strong, 180 degrees both engine first 12 hours post purchase
  2. Sucked up mud entering new creek/marina, both engines overheated, alarm came on
  3. Sea strainers were packed with mud, cleaned them and back flushed seacocks, ran engines at the slip, 160 - 170 degrees
  4. As part of service I was planning to do anyway: replaced all fuel filters, belts, starboard engine fuel primer pump and did the valve lash adjustment. Did not have the tool to set the injector height so that is on the to do list. Took boat out same day for test run. Engines ran at 180 degrees until on plane at 2000 +- RPMs, temps immediately spiked to 200+
  5. Replaced raw water impellers. No broken fins found. Removed end caps on heat exchangers. Looked mostly clean/good to me.
  6. I pulled the inside one off of both engines. I found very very small pieces of an old impeller in one, the port side. This could not be from the impeller I replaced in my opinion since none of the fins were damaged. I removed these pieces and then flushed with dock water, nothing came out/back. I unsuccessfully tried to remove the other end caps so water could move all the way thru. I could not figure out how to get to the last of the 5 bolts with the wrenches/sockets I had. That was next on my list as well.
    I purchased the .22 caliber cleaning rods to do this though I did not since I thought pushing the rod into a hole with other cap on would do more harm than good. Took the boat back out, same result.
  7. Mechanic started to flush the raw water side of port engine with barnacle buster, marina asked him to leave. Started engine 3 hours later to remove the barnacle buster.
  8. Removed, cleaned and reinstalled trans coolers on both engines. Replaced zincs. Looked mostly clean/good to me. Took the boat back out, same result.
  9. Flushed port engine aftercooler with barnacle buster (see video above) since this is the one the mechanic started with. Nothing looked bad to me in the flush. Too much grassy crap in the water so I did not start the engine to go out for a test.
  10. Ordered new raw water pump backing plates and various hoses from Carter Machinery this weekend. I recall seeing some minor grooves on the back of the plates when I changed the impellers, I do not what's acceptable, what's not, so I figured go ahead and replace them.
  11. My next step is to barnacle buster the port heat exchanger.
As I removed hoses/parts I back flushed with the dock hose/spray nozzle. The dock has amazing water pressure. I have not seen any signs of mud or blockage.
After you did #3 did you take the boat for a test run to up to plane to observe temps?

I look at all that was done in #4. Two things that could contribute to overheating were touched, the belt and valve lash. I'd review both.

There's been quite a few CSR guys that have sucked up mud over the years. Clean out the sea water strainers, maybe change impellers and away they went. With all the checks for blockages you've done I'm beginning to think mud ain't your problem at this point.
 
A couple of possibilities not addressed -
  • Did you physically pull the boat out of the water or dive on it to inspect and clean the intake grates under the boat?
  • Pull the exhaust hoses off the risers and inspect the exhaust "shower head" and back flush that?
  • You really need to get both caps off the Hx to ensure the tube bundles are clear.
  • The Hx caps have a divider in them to circulate raw water through one half of the Hx tube bundle then that water turns around and comes back through the other half of the tube bundle. Make sure those plastic dividers didn't get damaged and are bypassing the water flow.
A plugged aftercooler on the 3126 will not cause engine overheating.

I think I suggested this some time ago but to do a test and measure water flow at three or more engine RPM ranges. Remove gear cooler discharge hose and route a hose to a 5 gallon bucket and time how fast the bucket fills at idle, 1500, and 2500 RPM.

Once you check the box on the raw water side then move to the engine coolant side.
 
After you did #3 did you take the boat for a test run to up to plane to observe temps?

No, I wish I had, next step was the service interval work in #4.

We checked the belts multiple times, all good. I checked them again Sunday, still snug. I did ask my GFs brother-in-law, who did the valve lash (he used to be a Cat land/heavy equipment mechanic for 18 year) if the value lash could be contributing to the overheating, he said no.

With all the checks for blockages you've done I'm beginning to think mud ain't your problem at this point.

Agreed, I have been thinking the same.
 
A couple of possibilities not addressed -
  • Did you physically pull the boat out of the water or dive on it to inspect and clean the intake grates under the boat?
  • Pull the exhaust hoses off the risers and inspect the exhaust "shower head" and back flush that?
  • You really need to get both caps off the Hx to ensure the tube bundles are clear.
  • The Hx caps have a divider in them to circulate raw water through one half of the Hx tube bundle then that water turns around and comes back through the other half of the tube bundle. Make sure those plastic dividers didn't get damaged and are bypassing the water flow.
A plugged aftercooler on the 3126 will not cause engine overheating.

I think I suggested this some time ago but to do a test and measure water flow at three or more engine RPM ranges. Remove gear cooler discharge hose and route a hose to a 5 gallon bucket and time how fast the bucket fills at idle, 1500, and 2500 RPM.

Once you check the box on the raw water side then move to the engine coolant side.

No, I did not have the boat pulled. I asked the marina service shop about that after they kicked the mechanic out a few weeks ago. They said with the backwash I did, and they did as well, they did not think it was necessary at this point. I even asked them to replace the zincs and do a bottom paint for me to kill 3 birds with one stone/haul out, they said not necessary.

I pulled the exhaust hoses off on the starboard side to get access to the raw water impeller. I did not know enough then to check or do anything else.

Agreed to the HEX end caps, I am going to try that again.

I was not aware of the divider, I will try to check this.

My research and queries about the after coolers has suggested the same.

Thanks for the test and measure water flow suggestion, first time I am reading this. And I was just at CAT yesterday to order new hoses; I'll need to get a longer piece to route to a bucket. Great suggestion.

What are everyone's thoughts on buying a phone borescope and looking into things for a blockage?

Reading the comments here I think my next best step is to remove the heat exchanger(s), which means removing the expansion tank, which means draining the coolant. I was planning to drain the coolant when we did the regulators anyway. Once removed take them to a radiator shop. If I can't find one to clean/inspect them for me then soak them overnight in Barnacle Buster. All of this was on my short to do list to get service maintenance up to date anyway. Do all agree?

If yes, for those that have done this can you please share what seals, orings, parts, pieces, etc. I will need to put everything back together? I already have the regulators and rings for the HEX caps. I am asking because the CAT dealer here is not very helpful with marine applications. I got very lucky yesterday while there ordering hoses. My GFs brother-in-law was there as well picking up parts and came over to show and find the girl what I needed.
 
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Ha, easier said then done. On the port engine at first\second glance I was going to have to remove the expansion tank, hoses, friends and such, which meant draining the coolant; just to get to the last bolt, and I have some pretty nifty wrenches. My GFs cat mechanic brother-in-law had some nifty ones too and he was stumped.

I will take another look.

Please correct me if wrong as I have not done this myself... Not yet.
Based on what I have read in the other threads regarding the HEX, can both side end caps be removed without losing the coolant? I was under the impression only the front (side where water enters/exits) could be removed for inspection.

My other thought was exactly that of TT, if you're not planning to lift the boat, then get a diver under there with a light to check the intakes. I don't know your water conditions, or how long it took since you bottom was cleaned and the problem first started, but around me the growth rate is incredible in the summer. I will have barnacles in 2 weeks. That, along with your mud/grass scenario could have you blocked up.
Also, so we are all clear, you are having nearly identical overheating on BOTH engines? At the same run speeds? That makes me think something environmental is/was the root cause.
 

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