TAMD 71B Overheating

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PlanB

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Some time ago I posted a query about one engine in our Princess 435 overheating, and had very helpful suggestions. I waited to say "thanks" as I expected to report success in short order. Sadly, we have not been able to resolve the issue over several months effort, so humbly apologise for not responding before but wonder if anyone has any further ideas.

Starboard engine will overheat when taken to max revs under load (but not if kept under 1200 revs). Will quickly cool down when revs reduced to (say) 1000/1200 rpm. Will overheat again when revs increased.

Checked so far:
Raw-water impeller. (Renewed)

Raw-water filter. (Cleaned)

Thermostat. (Tested in boiling water)

Raw-water flow (Back-flushed with fresh water and ‘agua fuerte’).

Exhaust elbow (Replaced).

Heat-exchangers, charged-air coolers and reverse gear oil-cooler. Sonic cleaned and pressure tested.

Fresh-water pumps changed from one engine to the other.

Next Steps: Remove the thermostat?

Flush the fresh-water system; Radflush or similar?

Compression test engine for exhaust leak in head gasket?

All suggestions gratefully received.
 
Looks that you are going the right way

Thermostats best not put in boiling water it can stretch them but better heated and opening temp checked
 
Thanks - shouldn't have said boiling water - it was heated from cold and, as you said, opened at the right temp.
 
The AD41A's in my last boat looked hot under load, put the IR gun on them and they were fine, turns out there was just something wrong with the guage calibration. Lets hope after going through the efforts you have been through that its not that!
 
2 more suggestions.

Blocked exhaust/ melted causing excess backpressure and heat build up.

Blocked seacock/ air leak on pipework before sea water pump.

Check exhaust gas temp and hg reading.

Check raw water static pressure on positive side of system.

My 62a s in my boat, port engine always ran hotter than stb, did all coolers etc to find elbow blocked at sprayhead, all very simple and cost nothing!

Its all very easy to pay an engineer/ spend a fortune on parts when often its a simple problem.
 
Would it be worthwhile to test the fresh water/coolant for traces of exhaust gas to establish if there is a head gasket leak? I've heard this can be done but don't know how.
 
71b o/heating

Very quick reply as I'm at work..
Had very similar problems with our 71B. Eventually traced it to the impellor in the fresh water pump. It had sheared from the shaft and most of the time was all ok. Some times though it would come adrift and therefore not pump coolant.
I was at my wits end!
I pulled the front cover off the pump to find this problem....it's pretty easy to do with the pump in place, just an internal circlip and a bit of prying the lid of (a bit like a tin of paint)

PM me if you want more info, I've got an in depth understanding when it comes to the 71b's cooling circuit! :mad:

Good luck!
 
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[
Thermostat. (Tested in boiling water)



All suggestions gratefully received.[/QUOTE]


Having cooling problems,checked my engine thermostat in boiling water and it opened OK.However on the offchance decided to replace it anyway.
The problem was cured.
Despite apparantly being OK when removed and tested and appearing to be alright,my old thermostat was definately faulty.:(
 
Hmm. Yet again watching with interest. Had diesel bug which is now sorted (fuel polished) but can't understand why the sb engine overheats with exactly the same as the original post on this thread. Would be interested in the solution if it clears. Don't trust the boat at the moment which is a shame.
Changed impeller and checked no oil in water and no water in oil.
 
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PlanB said:
Would it be worthwhile to test the fresh water/coolant for traces of exhaust gas to establish if there is a head gasket leak? I've heard this can be done but don't know how.
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head gasket leaks are often difficult to pinpoint. If there's no oil involved, you wont find creamy dipsticks or filler caps.
However, I'd keep the blown gasket option at the very end, as its highly unlikely an overheating engine is dropping temp once the revs drop and you'd definitely have coolant loss (which I presume you don't)

V.
 
Had exactly the same problem. Now 100% cured. Did most of the usual as detailed in the original post which didn't fix it. Took the impeller off as starting to look for the problem from scratch again. There was a small amount of play in the shaft. Took the raw water pump off and the bearings and seals were all but non existent. Changed the pump, Jabsco replacement not from Volvo! A bit fiddly to change the gear from old to new. Sea trialled successfully. On the old pump, at high revs the shaft moves slightly and the back pressure from the exhaust was greater than the flow the damaged pump was capable of giving hence overheating at high revs and dropping when slowed down. it wasn't evident when checking the engine and water flow when on the moorings as the flow looked fine but clearly wasn't!
This has been a long ongoing problem and it only cost me about £500 in the end and was not an obvious problem but once found was a few hours work to swap the pump over, oh and a little bit of swearing because of the lack of room! A tip, get 3/8 x 1" UNC SS replacement bolts with the pump, the old ones were badly corroded and difficult to get off. I am absolutely delighted and the engines have never sounded so sweet!
 
I had the same problem on a tamd 71 many years ago. Checked all the usual stuff but eventually swapped the sea water pumps between engines and found that the overheat followed the pump.

I fitted a pump overhaul kit, when the old cam was checked against the new one it was found to be very worn.

All sorted.
 
I had hoped to try an overhaul kit but the flanges and mounting bolts that join the two halves of the pump were badly corroded and the centre holes were now slightly oval it wasn't worth taking the risk on mine. It had obviously been leaking for some time. I also found, and corrected, some botched work on the heat exchanger during the investigations. I suspect this fault was on the vessel when I bought her looking at the evidence of the work that had been carried out on this engine. It was probably why they sold her!
I have seen various very similar threads on various forums and apart from yours and mine have never seen a post with a solution for the problem. All fixed for a few hundred quid. It's amazing how many engineers told me the heads had gone and I needed new engines despite the lack of the common evidence of coolant/oil contamination :-). The only one who didn't was a friend of mine (John Blake - Thames) who gave me moral support via the telephone and persuaded me to keep it simple and continue to look at the obvious. :-).
Another firm had told me to flush the raw water through with acid (which transpired to being patio cleaner with the usual 'marine' mark up) despite me having evidence that the heat exchanger bores were clean. I'm only recording this on the forum to help others. I know it may come across as slightly smug (which it is of course lol) as it is the culmination of months and months of tinkering and heartache and what could have been very expensive in many ways if I had either listened to some of the advice I had been given or it had catastrophically failed whilst actually underway in the Bristol Channel!
Boating, it's fun isn't it lol.....
 
boatingdave said:
Had exactly the same problem. Now 100% cured. Did most of the usual as detailed in the original post which didn't fix it. Took the impeller off as starting to look for the problem from scratch again. There was a small amount of play in the shaft. Took the raw water pump off and the bearings and seals were all but non existent. Changed the pump, Jabsco replacement not from Volvo! A bit fiddly to change the gear from old to new. Sea trialled successfully. On the old pump, at high revs the shaft moves slightly and the back pressure from the exhaust was greater than the flow the damaged pump was capable of giving hence overheating at high revs and dropping when slowed down. it wasn't evident when checking the engine and water flow when on the moorings as the flow looked fine but clearly wasn't!
This has been a long ongoing problem and it only cost me about £500 in the end and was not an obvious problem but once found was a few hours work to swap the pump over, oh and a little bit of swearing because of the lack of room! A tip, get 3/8 x 1" UNC SS replacement bolts with the pump, the old ones were badly corroded and difficult to get off. I am absolutely delighted and the engines have never sounded so sweet!
Click to expand...
Discussed this with the tame (english speaking) engineer. He has measured the tempreture of the overheating engine at the exhaust elbow using a 'heat gun' whilst the engine is at full revs and says that it is quite cool (same temp as portside engine, no problems on that engine). He says the relative coolness of the elbow and the fact that both elbows are of similar tempreture would indicate that sufficient raw water is passing through the system and it can't be the raw water pump.
Any comment from you guys greatly appreciated as I sit here and quietly approach Wit's End from a southerly direction.
 
Having read some of the replies most of your fault finding has centred around the sea water system, have you removed the fresh water pump and checked the vanes on the pump, they do fall apart, ive just been involved with a 61a thats exactly the same set up, par the double heat exchangers.
 
volvopaul said:
Having read some of the replies most of your fault finding has centred around the sea water system, have you removed the fresh water pump and checked the vanes on the pump, they do fall apart, ive just been involved with a 61a thats exactly the same set up, par the double heat exchangers.
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Yup, swapped the fresh water pumps over engine-to-engine to see if the problem would migrate. No such luck. I am assuming then that it's not a fresh-water pump problem.
 
Just out of interest exactly what is "overheating", ie what temperature are you talking about,[both engines] as mentioned before, are you suffering coolant loss?
 
capsco said:
Just out of interest exactly what is "overheating", ie what temperature are you talking about,[both engines] as mentioned before, are you suffering coolant loss?
Click to expand...
The 'good' engine, the port side engine, the one with which we have no problems with at all, warms up to and then stays constant at around 70degrees C. irrespective of engine speed. The starboard engine will stay at 70degrees if the revs are kept around 1200rpm. If we then open up the engines to 2000rpm the tempreture gauge for the starboard engine will rise to 100degrees and the audible alarm will sound. Throttle back and the engine will steadily drop back to 70degrees. An IR heat gun has shown that the gauges for both engines are fairly accurate. There is a small amount of coolant loss on the starboard engine but we don't know whether this is causing, or is caused by, the overheating.
 
As its going off at 2000 rpm then its going to be something thats blatently obvious as the engine is no where near its rated rpm (2800) usually engines that suffer overheat it starts at just below its rated max rpm unless of course say the impellor has failed into pieces or there is a near total blockage of sea water to the inlet pipes.
 
volvopaul said:
As its going off at 2000 rpm then its going to be something thats blatently obvious as the engine is no where near its rated rpm (2800) usually engines that suffer overheat it starts at just below its rated max rpm unless of course say the impellor has failed into pieces or there is a near total blockage of sea water to the inlet pipes.
Click to expand...
We've checked and replaced the impeller. The original one was worn but not 'shredded'. We've back flushed the raw water system and there's plenty of through flow of sea water. The boat when moored will rev to max revs and will sit all day at 2000revs and there is no sign of overheating, only when out there, underload, does the engine overheat.
 
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