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8.1 Crusader 2008 overheating at high RPM only

A

allenb

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idling and moderate cruising at approx. 175 degrees F up to around 3000RPM . However at higher cruising speeds temp is creeping up to 190 degrees .... idle, trolling and low cruise to plane is fine; just higher up in the RPM range. Any ideas ? Single screw only 275 hours on engine ... Heat exchanger in salt water environment maybe? Any ideas from anybody .... hoses all look good, so does sea stainer and impeller ....thanks to all, allen
 
High power high heat usually caused by low raw water flow. Clogged rissers (over 4 years in salt service), clogged oil cooler (internal tubes), clogged HE, air leak at strainer cover, barnacles on hull scoop, and various raw water pump issues (impellor, worn cam, scored cover).
Further down the list is kinked or internal delam of suction raw water hose, stuck thermostat, air in coolant.
 
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impeller is original 275 hours ago ... inspection looks fine, not blades missing at all and no imperfections. thinking it might be heat exchanger itself on top of engine or oil tranny cooler down low to the side between engine mounts .... Formerly I owned the 454 Crusader and typically had this problem occaisionally with the U cooler for oil and tranny where the lower zinc often clogged the cooler causing overheating or poor ciruclation, but this newer 8.1 Crusader has a pass through oil tranny cooler and no zincs. So my first guess is the Heat exchanger, and it happens to be in an easy and accessible location being up top on the engine which is in a tight installation. Further thoughts
 
That tight install won't be much fun to troubleshoot. I agree w/ DD -> low raw water flow. Thoses inline coolers will clog just as easily as the older U style but not with the zinc 'flakes'. You may find a clear length of 1.25" ID hose helpful to isolate the cause.

I'd second that thought of verifying the strainers are not leaking air...probably much easier than getting to the engine.
 
mako mark, can you run me through the use of the clear hose ... are you saying to use it instead of the engine supplied hoses in certain areas and visually inspect to measure water flow? If so, what locations on the 8.1L Crusader do you recommend?

thanks ...

ab
 
Temporarily replace the factory hose with the clear hose - yes, that's the approach. any reduced or aerated flow is easy to spot with the clear hose. I usually start at the raw water pump and work towards the exhaust.
 
My 8.1's (2008 with 100 hrs) typically run at about 160-165 deg in mid range (3000 RPM). At higher cruise rpm 3600 - 3800 the temp starts running up to 180 - 185 and during WOT runs temps go up to 190. Remember, as the rpm goes up, the engines are putting out more power which equates to more heat that has to be eliminated by the cooling system. What has been your normal operating temps? Unless the temps you are experiencing are something new, it is my opinion that you do not have a problem. It is always a good practise to scan your gages while out running to be aware of any changes in operating conditions. If your not comfortable, change the impeller and see if things change.
 
we are single screw, typically temp tops out below 180 F at all times , so we are tackling the impeller in the next day or so. tight install so getting to almost anything other than thing up top is difficult ... This is 1996 2600 Pursuit inboard direct propeller shaft in tunnel / pocket drive. Need to be Gumby to get to anything so we'll see how tough a basic impeller replacement becomes. Have OEM replacement in hand so we will see. Then we will trouble shoot further if needed. Thanks to everyone so far. allen
 
which way do we rotate 15mm nut on serpentine belt tensioner to loosen tension and slide belt off? anyone give us a heads up? we were told the tensioner was prone to damage if handled wrong ... anyone can save us the headache and let us know please? many thanks. repair commencing in morning ... thanks to all of you .... allen
 
ALL tensioners don't like being mishandled. most require you to relieve the tension on the belt and then the belt. usually easiest to slide it off at a smooth idler pulley. with it being tight quarters, another set of hands may be of benefit.

A good inspection will show you which way to rotate the pulley on the tensioner. If not, and you pick the wrong direction, those belts don't stretch so it should be hard to recognizze the error.
 
Ok, here's how it played out. Checked intake below hull, checked sea strainer, all good, clean and sealed.

Plan A as advised by many of you: changed the impeller with OEM replacement. Not much issue, easier than I thought in our very tight install. got to it fairly easily and needed only a 15mm to turn back belt tensioner, remove belt and then loosen three 10mm screws with access through holes in the belt pulley mounted on front. All in all, probably a 45 minute job - start to finish. Surprisingly easier than the old 454 we had years ago. Front half of pump comes out with shaft and pulley leaving only impeller in housing on engine. Nicely thought out design of pump and replacement process. Up high and room to see it even in my ridiculous application. No gasket, just o rings. Impeller looked OK but soft, no blades missing, no tears, just a bit soft, etc.

Replaced with new impeller, new 3 small o rings on the little mounting screws so you can't drop them when pulling apart pump and one main one to seal the two pump halves together .... 45 minutes including taking our time and cleaning up O ring grooves from small sea scum etc.

Sea trial ..... BUT .... NO joy, No change ... Still high temp at high RPMs

Second Plan:

took 2 gallons of RYDLYME, mixed with water 1:1 ratio as instructed by manufacturer. Instead of following the recommendation to circulate in reverse after removing new impeller, followed a different review on their web site, where several bigger diesel engine guys just ran the RYDLYME through the raw water circulation loop mechanism as you would rinse with fresh water style valves. We had that valve already installed years ago. Removed the only zinc anode located in the Heat exchanger, Ran it for all 4 gallons till I saw change in color of exhaust water telling us Rydlyme product was throughout the raw water circut. Then let it sit for 4 hours. Then, long rinse with fresh water for 20 minutes , Then warmed the engine to normal at the dock , then sea trial on sea water again as per normal running conditions.

BINGO - Houston we seem to have green for go .... high RPMs and normal temp at 180F or so. Did not get an hour out there to really be sure since ocean was pretty snotty outside the channel and with much chop too so it was pretty nasty - but from initial run back and forth and out the channel and back twice at full speed, before getting slammed by easterlies, I must say the temps look good. Will keep you posted as I check it with better weather this week for a longer run. Seems like one or more of the coolers were fouling up but this Rydlyme just might have done the trick. If so its a great product instead of tearing down and trying to acid bath coolers. I will highly endorse it if I pass the next sea trial this week. Thanks to everyone for help on this. Allen
 
Allen: based on what you know so far, is your conclusion your HX accumulated some build up or scale that just reduced its heat transfer capability? Any idea on the suspected cause (local environment)? I know for many years, at the ocean, we never had an issue with the fine mesh on the A/C cooling water strainer. In our current berth, it clogs in as little as one week once the water warms up. It is something biological as a quick bath in the H2O2 eliminates it.
 
I did not even think that peroxide would work to clean out the strainer screen. Seems llike something fizzy and pH reactive always comes to mind. I am going to try this on a few things...Thanks Mark.
 
will no more tomorrow when I do longer sea trial but so far I assume it was heat exchanger or one of the smaller coolers for either the tranny or the oil which both run on the same raw water circuit. two product that can do this descalling exceptionally well it seems:

Barnacle Buster or Rydlyme... both seem very similar both biodegradable both enzyme based no acid non toxic able to be flused without any metal damage or rubber damage at all and both seem to descale real well. Both designed to be circulated for some hours in the loop after removing impeller in raw water pump OR run into the system as a solvent descaler and let sit for a longer period then flushed. I did the later mostly because I did not have ciruculating pump handy and the extra hoses to make up the ciruclating kit. Both companies sell pump circulating rigs for big and small applciations. Recommend you google both, If I am running cool again I am quickly becoming a big supporter of both and will buy or rig up a circulation bucket and pump to do as standard yearly maintenance. sure beat replacing cooler, I will report final after this weekends longer sea trial to all of you and thanks again/ allen
 
Al: I found out a while back peroxide is an oxidizer which is considered "environmentally friendly". Basically, in a concentrated form, it will chew up anything that is "alive" (organic). the key to making it work is to get the concentration up. In a pinch, you can use good old oxi-clean and a little water.

If you want to get a little first hand experience, mix up a little bottle and apply it to some weeds in the yard....
 
I was not concerned with organics with my8.1, all the literature and threads took me to basic impeller and raw water scaling etc as you can read above. I was thinking the heat and cooling mechanisms were all about lime deposits and scaling was mineral deposits of sorts from the heat and sea water interface. Therefore I looked for a descaling agents like Rydlyme and Barnacle Buster. Never looked at perioxide types so that is interesting. Have not finished final sea trial due to personal issues of late. Will do final sea trial run this week and report to everyone what the 4 hour Rydlyme soak accomplished (or not ). Thanks ! Allen
 
Thanks Mark,

Is there a obtainable source for higher concentrations of peroxide? "Medicinal" household use is only about 3% and mostly water. I am more than willing to experiment
 
Al:

I haven't spent much time looking so this sure isn't definitive. My assessment is buying liquid, via mail order, is cost prohibitive for any significant quantity as they treat is as hazmat. Three choices come to mind though I haven't had any luck with the first two. Pool supply/service companies (if in a larger area a 'spa service company' may exist as well. They use the 30-40% grades to "clean pools". Another choice is an Ag Supply house. Locally, we have a few but there isn't a "local demand" so there isn't any stock or established distribution channel. The last choice is to buy the "powdered form" (sodium percarbonate aka oxi-clean) and then mix up you own 'batch' driven by your specific needs.

Like I said earlier, it works great on organic 'growth' (e.g., slime at the water line); I wouldn't expect it to handle anything mineral based.
 
Ok, it's official. Rydlyme. Buy it. Circulate or soak your raw water system on you crusader to descale all aspects of the system and get your engine running as cool temps as new. We are back down to 175 degrees F now at high rpm. I understand Barnacle Buster works as well. Thank you all for all your input. Our problem was not our impeller, but it is replaced now anyway for good measure. Thank you all.
 
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