Temperature gauge.

[Laundryman]

3 or 4 mins at full revs and my Volvo 2020b overheat alarm sounds. No problem at normal cruising revs. I throttle back and generally the alarm dissappears. Although I treat the alarm with respect, I'm not sure that the engine is actually. overheating! No smell, no steam from the exhaust etc. I plan to flush the raw water side with Fernox and use an automotive rad flush on the circulating coolant. I have an electric automotive temperature gauge. Can I simply connect to the alarm sensor on top of the water pump and get a reasonably accurate reading? What would be a normal running temperature, 85 degrees? Thanks. Alan

 

[VicS]

The thermostat should begin to open at 75C and be fully open at 87C ( this info is in your owners manual) Therefore you'd expect the normal running temperature to be just a little above 75 but always l below 87.

I guess the alarm sensor you refer to is just the temperature sensitive switch for the warning light and buzzer, so no you cannot connect a gauge to it. Versions with a temperature gauge have a separate sensor for the gauge.

You need to validate the alarm and if genuine determine the cause before you get to stage of overheating smells or steam from the exhaust.

Checking the thermostat is one obvious thing to do but thats not so easy on this engine.

The temperature could be checked with an infra red gauge,


More likely a problem on the raw water side than the fresh water side I would think if the coolant has been changed at the correct intervals and salt water not entered,

Dirty heat exchanger ? bad pump impeller ? worn pump? restriction somewhere? bunged up exhaust injection point?

BTW I think the warning light and buzzer should come on at 95C

 

[reeac]

I had similar problem with a raw water cooled VP 2002. Turned out to be a thermostat stuck in the closed position. In those circumstances the engine can still get enough cooling via the bypass channel to cope with moderate revs. But overheats when you try to get more power out.

 

[Plevier]

I guess the alarm sensor you refer to is just the temperature sensitive switch for the warning light and buzzer, so no you cannot connect a gauge to it. Versions with a temperature gauge have a separate sensor for the gauge.

That's correct. However I fitted a temp gauge to a 2020D, if the B is the same it's dead easy. There is a drain plug on the heat exchanger. I think it was a metric thread maybe M12 or 14. You can get a gauge off ebay for about £5 with a male threaded sensor typically small BSP or NPT and an adapter to replace the drain plug for another £3 or so. Of course you need to wire it to 12V as well and make or buy a bracket for the gauge. Incidentally that is where VP fitted the sender for the optional gauge on de luxe installations.
See item 18 on http://www.marinepartseurope.com/en/volvo-penta-explodedview-7746410-25-2426.aspx

 

[Laundryman]

Okay, thanks to everyone. I have changed the impeller again, the exhaust elbow has done 100 hours, I have a new thermostat waiting to fit and I have one of those fancy( but cheap) infra red temp guns. I'm going to change everything which I'm sure will solve the problem. Thanks to Plevier for the info re the gauge. I'd feel better with something to keep an eye on. Alan

 

[Spuddy]

My 2002 did similar. Gave the exhaust elbow a good soak in brick cleaner and with poking got out quite a lot of carbon looking stuff. Worth looking at.