Bukh DV10 - Alarm and temperature warning light illuminates after 4/5 minutes of the engine running

[TollesSailor]

Good morning to you all.

My wife and I purchased a Sadler 26 (in Sept 23) and only recently has she gone back into the water. The first time since we have owned her.

I've worked my way through a couple of issues with warning lights (Oil pressure and Amp) but I'm facing a problem that I could really do with some advice on.

The engine starts fine, I can see water coming out the back (not vast quantities but enough to suggest it is coming in and circulating). After about 4/5 minutes we start to hear an alarm but it's very quiet (we know the alarm is fine as it activates during the ignition sequence). I can then see that the warning lamp for water temperature has illuminated, albeit not very bright. The engine doesn't seem that hot.

I'm wondering whether this may be an issue with the water temperature sensor but am unsure how to prove or disprove this. The sensor has a single cable connected to one of the 2 terminals (nothing on the other) and from what I can see this does run to the water temperature warning lamp.

 

[littledancersadhu]

My freind had this issue.

clean out all the water ways
new impellor
clean the fresh ware strainer
test the sensor heating up in a pot with a temp sensor.
All the usual culprits
do the same with the thermostat, need to check mine!

 

[vyv_cox]

A well-known problem with these engines is blockage of the water flow at the entry point behind the flywheel. It is possible to remove the two Allen bolts holding the fitting without removing the flywheel but you may need to shorten an Allen key to do it. Carbonate deposits here need to be removed to restore full flow.

 

[TollesSailor]

My freind had this issue.

clean out all the water ways
new impellor
clean the fresh ware strainer
test the sensor heating up in a pot with a temp sensor.
All the usual culprits
do the same with the thermostat, need to check mine!

Really appreciate this, thank you.

That's a great idea about testing the sensor in a pot. I hadn't realised that was possible.

 

[TollesSailor]

A well-known problem with these engines is blockage of the water flow at the entry point behind the flywheel. It is possible to remove the two Allen bolts holding the fitting without removing the flywheel but you may need to shorten an Allen key to do it. Carbonate deposits here need to be removed to restore full flow.

Thanks for this, I hadn't even considered a blockage to the water flow. I'll have to look at the DV10 engine diagram to work out where the entry point is.

Appreciate this.

 

[VicS]

You say that the light comes on but "not very bright" and that the alarm sounds " but very quiet".

I'ts possible that there is some resistance due to bad connections in the wiring causing this or a bad sensor

BUT
You mention two terminals on the sensor ........ one is for the light and alarm, the other is for a temperature gauge. I wonder if you are using the wrong one . Easy to check. the alarm sensor should show open circuit to earth while cold or at normal running temps but should show zero ohms to earth if overheated. The gauge sensor will show a resistance to earth ( sorry don't know what) which will decrease as the temperature rises.

Check out the sensor and connections before remedies for overheating especially if you dont think it is overheating ........... An infra red temperature gun would be useful to check the actual engine temperature. ( mine came from Lidl ! )

 

[LittleSister]

I suspect bad connections, or possibly a failed sensor. I doubt, but can't rule out, that the engine is actually overheating as when it does the alarm should sound loud and the lamp fully illuminate.

Note also that the simple small circuit board (usually located behind the gauges) which connects the three (or whatever) sensor wires and lamps to the single alarm buzzer, is sometimes a source of problems. I've read of people having problems with it sounding quietly but all the time. (There are various old threads on this.) I doubt the circuit board and it's components are the problem here as it is fine for the first few minutes, rather than sounding all the time.

I'd clean up the connections to that board (don't forget to note which wire goes where - it's a bit confusing to follow the wiring/numbering on the wiring diagram) and to the sensor. You could run a temporary wire from the water temp terminal on that board to earth to check that it properly sounds and lights when thus connected ith Note also there are (probably) intermediate multi-wire block connectors between the instruments and the engine - another potential, but less likely, source of dodgy connection.

If still no joy, then check the operation of the sensor is as per VicS's post above. (If you need to replace that there's an old thread where someone found, with some difficulty, the correct sensor without paying the ridiculous inflated Bukh spares premium (he got it from Furneux Riddell, if I recall correctly, and part of the problem he faced that the size of the correct sensor was incorrectly listed in their catalogue at the time).

I'm not aware there are different temperature alarm sensors for direct (seawater) cooling versus indirect (freshwater cooling + heat exchanger) cooling, but note there are different thermostats for the two types of coming system. If there are different sensors, then having the wrong sensor, or the wrong thermostat, for the cooling system you have could be a problem Seawater cooled should run IIRC 50 to 75 degrees C, and freshwater 70 to 95 degrees C.

I doubt it is actually an overheating problem, but if it is then suspect the cooling 'poker' connection just behind the flywheel is partially blocked by scale, as mentioned above (lots of old threads on this, including how to get it out without removing flywheel), but also check (a) the seawater pump for wear or damaged , (b) the exhaust elbow for blockage.

Note there's a Bukh Facebook group where you might find info or suggestions additional to that available here.

 

[TollesSailor]

You say that the light comes on but "not very bright" and that the alarm sounds " but very quiet".

I'ts possible that there is some resistance due to bad connections in the wiring causing this or a bad sensor

BUT
You mention two terminals on the sensor ........ one is for the light and alarm, the other is for a temperature gauge. I wonder if you are using the wrong one . Easy to check. the alarm sensor should show open circuit to earth while cold or at normal running temps but should show zero ohms to earth if overheated. The gauge sensor will show a resistance to earth ( sorry don't know what) which will decrease as the temperature rises.

Check out the sensor and connections before remedies for overheating especially if you dont think it is overheating ........... An infra red temperature gun would be useful to check the actual engine temperature. ( mine came from Lidl ! )

Good afternoon VicS.

Really appreciate you taking the time to reply and for the really helpful suggestion. I've sourced myself a reasonably priced infra red temp gun and will take a further look this coming weekend.

Thank you

 

[TollesSailor]

I suspect bad connections, or possibly a failed sensor. I doubt, but can't rule out, that the engine is actually overheating as when it does the alarm should sound loud and the lamp fully illuminate.

Note also that the simple small circuit board (usually located behind the gauges) which connects the three (or whatever) sensor wires and lamps to the single alarm buzzer, is sometimes a source of problems. I've read of people having problems with it sounding quietly but all the time. (There are various old threads on this.) I doubt the circuit board and it's components are the problem here as it is fine for the first few minutes, rather than sounding all the time.

I'd clean up the connections to that board (don't forget to note which wire goes where - it's a bit confusing to follow the wiring/numbering on the wiring diagram) and to the sensor. You could run a temporary wire from the water temp terminal on that board to earth to check that it properly sounds and lights when thus connected ith Note also there are (probably) intermediate multi-wire block connectors between the instruments and the engine - another potential, but less likely, source of dodgy connection.

If still no joy, then check the operation of the sensor is as per VicS's post above. (If you need to replace that there's an old thread where someone found, with some difficulty, the correct sensor without paying the ridiculous inflated Bukh spares premium (he got it from Furneux Riddell, if I recall correctly, and part of the problem he faced that the size of the correct sensor was incorrectly listed in their catalogue at the time).

I'm not aware there are different temperature alarm sensors for direct (seawater) cooling versus indirect (freshwater cooling + heat exchanger) cooling, but note there are different thermostats for the two types of coming system. If there are different sensors, then having the wrong sensor, or the wrong thermostat, for the cooling system you have could be a problem Seawater cooled should run IIRC 50 to 75 degrees C, and freshwater 70 to 95 degrees C.

I doubt it is actually an overheating problem, but if it is then suspect the cooling 'poker' connection just behind the flywheel is partially blocked by scale, as mentioned above (lots of old threads on this, including how to get it out without removing flywheel), but also check (a) the seawater pump for wear or damaged , (b) the exhaust elbow for blockage.

Note there's a Bukh Facebook group where you might find info or suggestions additional to that available here.

Many thanks LittleSister.

Thank you for such a comprehensive reply, I must say you have given me a lot to think about and, increased my to-do list.

I had seen the thread about Furneux RIddell and if needs be I will source a sensor from them. Paying £170+ (quoted by other sites for a genuine Bukh spare) is not something I would want to do.

Really appreciate your advice.

 

[neil_s]

My DV20 has a temperature sensor with two blade connections. One is for the dashboard temperature light and the other is for a temperature gauge - that might not be fitted. Are you sure you are connected to the correct blade?

 

[VicS]

My DV20 has a temperature sensor with two blade connections. One is for the dashboard temperature light and the other is for a temperature gauge - that might not be fitted. Are you sure you are connected to the correct blade?

Post #6 ......... Great minds work alike !

Good afternoon VicS.

Really appreciate you taking the time to reply and for the really helpful suggestion. I've sourced myself a reasonably priced infra red temp gun and will take a further look this coming weekend.

Thank you

I cannot believe that the engine temperature would reach the the alarm point in 4 to 5 minutes.

.

 

[TollesSailor]

Post #6 ......... Great minds work alike !

I cannot believe that the engine temperature would reach the the alarm point in 4 to 5 minutes.

.

Good morning VicS.

That was also my thinking, could it really get to the alarm point in such a short space of time?

Given the issues I have unearthed and resolved with the wiring (so far), I do wonder whether this could be a case of the cable being on the wrong terminal.

I'm planning to take a look at the weekend and will report back.

Thank you to everybody for their guidance and suggestions.

 

[TollesSailor]

Good morning to you all.

I'm really pleased to say that having followed the advice and guidance you provided, I managed to run the engine for 30 mins without any hint of a temperature warning light or, alarm.

The problem turned out to be the temperature sensor. After testing it, as suggested by VicS, I found that the cable was on the incorrect terminal. I managed to swap this last weekend but didn't have a tide to run the engine.

Thank you ever so much for the guidance and suggestions.

 

[davidmh]

On the DV20 the temperature sensor has 2 spade terminals , they are different sizes, probably to avoid a wrong connection. I find that the connectors are very easy to dislodge when you are working on the engine, and the female part needs to be kept crimped up tight.
David MH