Running engine without thermostat

[gavin400]

Investigating possible causes of my Volvo md1 emitting large quantities of black soot and boat speed being only a couple of knots.

So far. have unjammed the cold start device which was jammed on and have cleared a blocked port in the exhaust manifold (gunked up with carbon deposits).

The exhaust bend is new, so is not blocked, and the air filter is clean.

I took off the thermostat housing yesterday only to discover there is no thermostat - the engine has been running fine since i've had the boat (10 years).
I had the engine serviced immediately after buying the boat and one of the items on the invoice was a replacement thermostat - I can only conclude that it was never fitted (or else its completely disintegrated!).

The question is - has running the engine with no thermostat done any harm?


Many thanks

Gavin

 

[KAL]

I think I'm right in saying that the thermostat acts as a bypass and only opens up if gets too hot, allowing cooling fluid through to the affected area. Without it, the fluid just circulates everywhere as if the thermostat was actually open. This way, you've just been cooling areas that didn't need cooling.

Someone more knowledgable than me might come on in a second to confirm or correct...

 

[PCUK]

The thermostat maintains the engine at the correct temperature by opening and closing to adjust the heat. This gives maximum power and efficiency and allows the engine to warm up much faster than without a thermostat. Having no thermostat will have had no adverse effect on the engine itself apart from not running at maximum efficiency and apart from watching the temperature gauge you would not have noticed any difference with or without the thermostat.

 

[VicS]

Investigating possible causes of my Volvo md1 emitting large quantities of black soot and boat speed being only a couple of knots.

So far. have unjammed the cold start device which was jammed on and have cleared a blocked port in the exhaust manifold (gunked up with carbon deposits).

The exhaust bend is new, so is not blocked, and the air filter is clean.

I took off the thermostat housing yesterday only to discover there is no thermostat - the engine has been running fine since i've had the boat (10 years).
I had the engine serviced immediately after buying the boat and one of the items on the invoice was a replacement thermostat - I can only conclude that it was never fitted (or else its completely disintegrated!).

The question is - has running the engine with no thermostat done any harm?


Many thanks

Gavin

It wont have done it any favours. It would have been running cold which could/would have led to condensation in the oil. Also the oil would not have thinned out to the "right" viscosity . On the plus side though corrosion and scaling in the cooling circuit may have been less.

If it were mine I'd fit a new one. Expensive but available from Keypart.

 

[Dave_Seager]

On some engines, including some Volvos, removing the thermostat can actually cause overheating. This is because, when the thermostat opens the main cooling passages it also close the bypass. Without a thermostat the flow through the bypass reduces the main flow.

However, if you have not noticed your engine overheating the lack of a thermostat has probably not done much damage although there may have been extra wear as the engine will have taken longer to get up to working temperature.

 

[Lakesailor]

The thermostat maintains the engine at the correct temperature by opening and closing to adjust the heat. This gives maximum power and efficiency and allows the engine to warm up much faster than without a thermostat. Having no thermostat will have had no adverse effect on the engine itself apart from not running at maximum efficiency and apart from watching the temperature gauge you would not have noticed any difference with or without the thermostat.

On some engines, including some Volvos, removing the thermostat can actually cause overheating. This is because, when the thermostat opens the main cooling passages it also close the bypass. Without a thermostat the flow through the bypass reduces the main flow.

However, if you have not noticed your engine overheating the lack of a thermostat has probably not done much damage although there may have been extra wear as the engine will have taken longer to get up to working temperature.

On many engines, especially those based on road going vehicles the thermostat does double duty. As well as providing a quick heat-up to the proper temperature to avoid oil being used at a low temperature and to encourage the evaporation of condensates from the inside of the engine, as others have said, it creates a scavenging effect in the waterways of the cylinder head. If the housing is empty the water chooses the path of least resistance and flows straight out of the engine. This can leave hot spots where the water is not circulating properly.
Even if you wanted to run without the thermostat it's wise to leave a plate in the housing with a restriction to encourage the scavenging water flow. (I have used the plate from the thermostat with the valve mechanism removed). But really you want to know why you are doing it if that is your chosen route.

The answer is to fit a thermostat and ensure a longer life for your engine.

 

[VicS]

On some engines, including some Volvos, removing the thermostat can actually cause overheating. This is because, when the thermostat opens the main cooling passages it also close the bypass. Without a thermostat the flow through the bypass reduces the main flow.

On many engines, especially those based on road going vehicles the thermostat does double duty. As well as providing a quick heat-up to the proper temperature to avoid oil being used at a low temperature and to encourage the evaporation of condensates from the inside of the engine, as others have said, it creates a scavenging effect in the waterways of the cylinder head.

The description in the workshop manual, http://boatinfo.no/lib/volvo/manuals/md1-d1-md2-d2.html#/30 implies that this does apply to the MD1

 

[Billjratt]

The reason the thermostat was missing in the first place needs to be investigated and corrected. I'll bet there's restricted galleries somewhere that need the salt cleaned out.
I'd also lay bets on a similar situation "somewhere" in the exhaust system although you say its been decoked. Are you sure the rubber pipe hasn't delaminated - like how old is it....?

 

[Tony Cross]

Investigating possible causes of my Volvo md1 emitting large quantities of black soot and boat speed being only a couple of knots.

So far. have unjammed the cold start device which was jammed on and have cleared a blocked port in the exhaust manifold (gunked up with carbon deposits).

The exhaust bend is new, so is not blocked, and the air filter is clean.

I took off the thermostat housing yesterday only to discover there is no thermostat - the engine has been running fine since i've had the boat (10 years).
I had the engine serviced immediately after buying the boat and one of the items on the invoice was a replacement thermostat - I can only conclude that it was never fitted (or else its completely disintegrated!).

The question is - has running the engine with no thermostat done any harm?


Many thanks

Gavin

Is it not likely then that your injectors are "gunked up with carbon deposits" and this may be your problem? I suspect the missing thermostat is a red herring....

 

[wotayottie]

Wouldn't worry. It's an old engine and built much more heavily than modern converted earthmoving engines. I would try putting in a thermostat and then give the engine a god long reasonably loaded workout to burn off any carbon possible. likely everything will be ok, but if it isn't you can go from there.

 

[Halo]

Wouldn't worry. It's an old engine and built much more heavily than modern converted earthmoving engines. I would try putting in a thermostat and then give the engine a god long reasonably loaded workout to burn off any carbon possible. likely everything will be ok, but if it isn't you can go from there.

+1

The MD1 was built like a brick outhouse - i.e. very solidly. I expect the black smoke (which is unburnt fuel) is a result of an injector getting blocked or choked as the engine has been running cold for too long. I would put some diesel treatment in the fuel (pre mix some of it in a jerry can) before running long and hard as described by wotayottie. This could well sort out the problem for you. If not it may be necessary to have the injector serviced (not sure where as it is a very old engine.)
Incidentally I ran my very old MD1 on F1 0W40 motor oil for many years. I did this because the oil was so thin when cold that I could actually hand start her - any other oil and the viscous drag of the oil meant I could not hand start. The concenus on this forum is to use very basic mineral oil on old engines but in your case the fully synthetic may be an exception where it is worth it - after all you only need 1 litre. It certainly did my engine no harm and it may get youout of a scrape if (like me) you are not getting much charge out of the dynastart and flat batteries are a potential hazard.
best of luck and let us know how you get on
Martin

 

[gavin400]

The reason the thermostat was missing in the first place needs to be investigated and corrected. I'll bet there's restricted galleries somewhere that need the salt cleaned out.
I'd also lay bets on a similar situation "somewhere" in the exhaust system although you say its been decoked. Are you sure the rubber pipe hasn't delaminated - like how old is it....?

The rubber hose is brand new, it was changed along with a new steel exhaust elbow.

 

[gavin400]

Many thanks for all the helpful advice.

There is a brand new, boxed thermostat on the boat - probably the one the engineer intended to install!

The engine can still be hand started fairly easily, so I guess there's maybe not too much wrong.

The oil is just cheapo supermarket stuff.

I did think about removing the injector and got as far as removing the retaining plate/bolts, but the injector wouldn't budge and I was scared to do any damage (apparently there is a very particular brass washer that must not be damaged).

I will replace the thermostat, put in a fuel additive and give it a good blast - although taht will have to wait a few weeks until back in the water.

 

[scottie]

The injector fits a copper sleeve which is water cooled they have been known to come out with the injector this also means that NO washer should be fitted under the injector if you do remove the injector drain the water from the cylinder block first.