Beta 38 - overheating issues.

[Hartlebury lad]

Hell again all.

 

I have a Beta 38 engine with overheating issues, with resultant coolant losses. There was coolant in the bilge all summer due to 3 or 4 overheating episodes, with regular topping ups needed so the coolant was eventually water only.

 

I identified moisture slowly dripping from an virtually inaccessible ( weak) hose at the front under the alternator which stopped when the pressure cap was opened.(less pressure)

Anyway, I refilled yet again with a decent anti freeze mixture concentrate. I bled the skin tank when it was pressurised, topped up again, and all seemed well again for a few weeks. No weeping and leaking - maybe due to the cooler canal temperatures too!

 

But I am back to square one again last weekend- the engine was started, ticking over for fifteen minutes, then worked hard to get out of the marina in a stiff breeze. Within ten minutes of leaving, steam was seen coming from under the panels. Sure enough, lower coolant level. But the skin tank was stone cold, although the block was piping hot.

 

Whats the likely cause? I am suspecting a faulty thermostat now in the first instance, which fails to open properly causing pressure in the block etc? Or maybe air getting in via the tiny bit which water previously was leaking out? The pressure cap itself is not the tightest fit also in fairness as it goes 360 degrees sometimes before finding the locating lugs.

 

or have I answered my own question?

[WotEver]

Did you bleed the skin tank?

[Bee]

What I would do. Fix the hose, might not be too bad once you get the spanners out. Drain the lot out and start again. Open the bleed point on the skin tank or loosen the top hose into it till you know its full. Loosen a high hose on the engine till you know that's full as well. Start and keep checking bleed points / loose top hose and see what happens. Temp. gauge? if it just gets hotter and hotter remove the stat and it should all be OK. If not I dunno.

[blackrose]

Just to clarify, has it ever run properly without overheating - and not on low revs on a canal but pushing hard on a river?

Did you bleed the skin tank?

 

I think so.

 

Anyway, I refilled yet again with a decent anti freeze mixture concentrate. I bled the skin tank when it was pressurised...

[BargeeSpud]

Is the engine tray dry?

 

You might not find a sign of leakage on the engine, but if there's water in the tray, then it might not be a simple case of rain water getting in. I had this same overheating problem with my Shire on a previous boat, couldn't find a leak anywhere but I had water in the tray. Because I hadn't the time to clean it out right away (lazy B, I admit!) & access wasn't easy, I kept an eye on the level which didn't seem to change & I foolishly ignored it until I found I was topping up by about a litre per day, so I stripped all the boards surrounding the engine out, went around the whole engine as far as I could reach with a mirror & torch & found a leak at the bottom of the water pump which hadn't been noticeable visibly or physically whilst the engine was hot.

 

This probably won't apply in your case, it only illustrates that leaks can be a pig to find. Hope its something simple to fix, good luck.

[Tony Brooks]

Temp. gauge? if it just gets hotter and hotter remove the stat and it should all be OK. If not I dunno.

 

No, that will simply be covering up a faulty. In fact it will probably just take longer to get hotter and hotter.

 

I have heard a few cases where the expansion in the water as it heats is too great for the volume in the manifold header tank so when it cooled air was allowed into the engine itself. Then when topped up the air got trapped and was passed into the skin tank where it got trapped. The cure was to fit an additional header tank. However I would make considerable efforts to ensure there are no leaks.

 

I would try to beg or borrow a cooling system pressure tester and pressurise the system to 12 to 15 psi when the engine is not running. If the pressure falls you have a leak that needs finding and as the engine is cold the water will not be evaporating as soon a sit leaks out. Then remove the tester and get the engine right up to running temperature. Refit the tester, do not pressurise and run the engine. If the pressure rises and keeps on rising I fear you will find a head gasket problem.

 

Refilling hot engines with cold water can distort the cylinder head. if you are going to do it refill with boiling water but better leave the engine to cool on its own.

[Hartlebury lad]

Thanks all so far.

 

The engine has previously run well - it is an Evans and Son hull, with a slightly undersized skin tank, so I am always cautious and try to keep an eye on things. I am aware of the shortcomings and reputaion on this. The boat is well used, especially on decent straights when appropriate. I am hoping to do The Weaver and Stourport ring this year so it needs sorting.

 

I bled the skin tank when draining the whole system and refilling.

 

The water is gathering in the tray under the engine - I know because I took out a litre or more of blue water with an extraction pump yesterday.

 

Tony may have a good point to look for, and the head development is worrying, although the oil is good and there is no obvious leak around the edge of the head. I will ask my engineer about a pressure tester. I have never added cold water to a hot engine.

 

No one has mentioned the possibility of an intermittent jammed shut thermostat - especially given the fact the skin tank was so cold. I am sure the connecting pipes were only warm due to radiated heat and not passage of fluid. Perhaps a change of pressure cap and/or removal of the thermostat may be the easiest next option! The suspect hose replacement will entail engine removal or much cutting out of timber bulkhead panels around pipes and cables!!!

My engineer reckons builders should spend a year or two as RCR type engineers before being allowed to design and build ......

Edited January 26, 2016 by Hartlebury lad

[mick55]

Just to advise you,under no circumstances run this engine without a thermostat in the system,the Beta/Kubota will boil its Jaffas Off without one and when it does you will have no warning as it boils in the block,as the temp gauge/switch sender is located in the cylinder head which will be cooler.

[mick55]

Just picked up from your post that it is an Evans and Son shell and you say that the skin tank is slightly undersized,you will find that it is very undersized,for a Beta 38 you should be looking for a minimum skin tank area of 11 square feet,what cooling area does your boat have?

The Beta range of engines are very robust and will handle high temperatures very well but they do have their limits,it sounds very much like you have a water leak somewhere and a pressure test is a very good idea,as from my experience I doubt the engine will have a major fault.

[blackrose]

Just picked up from your post that it is an Evans and Son shell and you say that the skin tank is slightly undersized,you will find that it is very undersized,for a Beta 38 you should be looking for a minimum skin tank area of 11 square feet,what cooling area does your boat have?

 

I had an undersized skin tank for my Isuzu 55 and I tried everything to cure it, but in the end only an additional skin tank could solve the problem. I think the factor for calculating skin tank area is 1ft square per 4 - 5hp.

 

However, while my overheating issue was always there from the start, it sounds like the OP's engine used to run without overheating as much as it does now, so something has obviously changed. I wonder if there are any blockages in the cooling system?

[Iain_S]

Quite often when a cooling system is drained and refilled, there is still some air left in it after bleeding. I have come to the conclusion that there is quite a lot of air disolved in tap water.

 

On the LandRover, it collects in the heater, resulting in cold demisters; on a boat with a skin tank, it collects at the top of the skin tank, and stops the circulation of water. When everything heats up, the air expands a lot more than the water, which may lead to water being expelled from the "radiator" cap.

 

The bit about hoses being hot and skin tank being cold might suggest this is the problem.

 

In the absence of any obvious leaks, it might be worth refilling and bleeding again, and bleeding the skin tank again each day until (hopefuly!) no more air comes out.

[Bee]

Just to advise you,under no circumstances run this engine without a thermostat in the system,the Beta/Kubota will boil its Jaffas Off without one and when it does you will have no warning as it boils in the block,as the temp gauge/switch sender is located in the cylinder head which will be cooler.

I would have thought that it would just stay cool, but you are right in that the temp sender can be in an air pocket.