Advice needed. Old engine, strange cooling

stuhaynes

stuhaynes

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I'm not going to make any apologies, but I've asked for advice on another forum I respect as well. This has been bugging me for years and now it's time to do something about it if I can.

The engine on our boat is original, a Coventry 'Godiva' 4 cylinder diesel, that's 60 years old. The cooling system was a sealed system when the boat was built, but sometime more than 25 years ago the original system was removed and replaced with a raw water type. The raw water does not pass through the engine but instead is injected directly into an exhaust manifold sleeve.

With this system the engine temperature never reaches more than 100 degrees fahrenheit. This has got to affect both performance and fuel consumption, not that you'd think so if you were to sail her. She seems capable of driving uphill and doesn't like diesel at all!

I want to increase the engine temperature to a compromise 70-80 degrees centigrade. This will help the engine and enable the oil to do its job properly.

My question is this. Does anyone know of a simple system that is capable of adjusting the cooling water, reliably, to affect the engine temperature? Restricting the water flow at the seacock is not an option because of the dangers of blockage.

Any thoughts? :confused:
 
The water in the block doesn't get cooled. There is no water in the block. The hot exhaust gases are cooled in the manifold, the engine doesn't get a chance to get warm, this is the problem.

I'm looking at it this way. The ambient temperature of the block after say 30 minutes running is 98 fahrenheit, blood heat. This is achieved by the volume of water cooling the manifold. If I were to turn the water off at the seacock, the engine would melt. Somewhere in between there needs to be a system that automattically regulates the water supply so that the temperature of the dry engine falls into a more acceptable range, say around 80 degrees centigrade. If this is possible it would then be possible to hook up a calorifier, free hot water etc.

I'm a bit stumped, must admit.....:(
 
stuhaynes said:
The water in the block doesn't get cooled. There is no water in the block. The hot exhaust gases are cooled in the manifold, the engine doesn't get a chance to get warm, this is the problem.

I'm looking at it this way. The ambient temperature of the block after say 30 minutes running is 98 fahrenheit, blood heat. This is achieved by the volume of water cooling the manifold. If I were to turn the water off at the seacock, the engine would melt. Somewhere in between there needs to be a system that automattically regulates the water supply so that the temperature of the dry engine falls into a more acceptable range, say around 80 degrees centigrade. If this is possible it would then be possible to hook up a calorifier, free hot water etc.

I'm a bit stumped, must admit.....:(
Click to expand...

Can't you fit a ball valve after the sea water strainer [so that any potential blocking debris has been removed] and experiment with different degrees of turning off? A more respectable way is to fit a restrictor plate with a set size of hole in it but you would need to know what sized hole was needed. This was a ploy used to cure overheating in high performance MG s - remove the thermostat and fit a restrictor plate.
 
Is this engine aircooled or oil cooled? There must be some means of cooling the cylinder. If the water is just being passed through the exhaust manifold and then injected into the exhaust pipe it is not cooling the engine, so no amount of manipulation of flow will alter the temperature of the block.
 
I'm with Tranona here, something just doesn't stack up. Your block will melt if it is not cooled some way. Pouring water into the exhaust will only cool the exhaust. Are you sure it is not channeled through the block before going into the exhaust?
What has happened to or what is in the channels of the old sealed system, it was there for a reason.:confused:
 
Heat exchanger?

I know it seems obvious, but why do you not re-fit some sort of closed circuit, heat exchanger type cooling system or a 'keel cooler' as was originally employed?

However, you say that the engine is 60 years old. If it is still running well after reqular use for all these years without problem then there cannot be much wrong with the way you have it installed or the way you are looking after it!
 
Reinstate heat exchanger cooling for my money.

However, There must be (over)cooling taking place. Is the water pump attached to the engine block? In this case the delivery to the manifold is a bypass, most water is going straight into the block, and what you have is a stuck open or missing thermostat.
 
It might be profitable to have a closer look at the engine; in all the external pipes you may have missed two connected between the exhaust manifold heat exchanger and the engine block. They could well be underneath.

I did a Google and came up with quite a lot of "possibles"

here's one for starters (clicky)

and another

I didn't find a picture of a four cylinder version, but as you can see from the Bath University picture above, there's a helluva lot of plumbing around.
This type of engine was designed (as are many industrial units) to have a lot of addons to power hydraulic pumps and so on, and it may well be that a circulation pump appears to be something else.

As others say the block has to be cooled and as CC were well known for their marine engines the heat exchanger cooling system could have been designed to be well integrated into the overall package (unlike more modern units where they are clearly add-ons to a base unit).

In essence find the water pump and possible thermostat, adapt to a modern replacement or fit a restrictor.

I had fun looking for you - and answered a lot of questions about car engines.

Read around if you have some interest in some of our lost industrial heritage.
 
I've had more of a chance to examine the original engine manual and got the torch out. I must say that when I first looked at this problem I was really confused. A close look
ended up with more confusion initially, but I'm halfway to an explanation now. Most of the original cooling system is still there, but it's been altered.

The original layout shows a sealed fresh water system that travels through the block exiting through the cylinder head to the top of the header tank. From the header the water passes to twin heat exchangers attached to the sump, one on each side. The heat exchangers have 2 chambers each, the outer chambers containing pumped cold 'sea' water. This cools the sealed system. The sea water then cools the exhaust manifold jacket and away.

The story so far. The original manual shows a 'vacumn and pressure relief valve' on the header tank, but no thermostat. This allows the fresh water system to pressurize to 4PSI above atmospheric, thus raising boiling point. As the sealed system cools the 'vacumn relief' side of the valve allows air in to relieve what would become a vacumn in the system. This valve is missing completely.

The system has been re-plumbed. The fresh water connection between the cylinder head and the header tank has been completely disconnected and replaced by a connection to the 'salt' cooling system. I haven't been able to get to the other side of the engine to see how the used 'salt' water leaves the boat. I'll post when I know more. This renders the 'fresh' side of the system redundant.

This explains the excessive engine cooling and as I see it will ultimately lead on to serious engine problems, or blockage, if I don't do something about it. There must have
been a good(?) reason for doing something like this but at this stage I'm guessing. The engine was stripped and examined in 1979 and there was no mention in the report (which I have) of the alterations then. I'm going to try and contact a previous owner from this time to see if I can find the reason.

I'll re-post when I know more.
 
Sounds like it was originally an ordinary pressurised system such as you will find in any car. the pressure and vacuum release valves are built in to the filler cap on the header tank. The pressure release mechanism is obviously enough the spring loaded part, but the vacuum release mechanism is usually the metal washer on the end of the spring loaded plunger, and it is not at all obvious how it works. Any modern car pressure cap / header tank assembly that fits the existing pipework, and working at 4psi, can be substituted.

Most likely the heat exchanges became clogged causing overheating, and rather than go to the cost of replacement, someone simply diverted raw sea water through the engine. If so, the sooner its put to rights the better!
 
I know naathing

I am curios tho. Aside from Its good to know how your engine works incase it goes wrong. and I realise that I would be better to be getting up to temperature.If the engine is 60 years old and the water system has been like that for 20 years or so. I thought the phrase would be"if its not broke dont fix it ? It would be terrible to put strain on some thing when its running so reliably. Or is a boat that is new to you ?
 
fergie_mac66 said:
I am curios tho. Aside from Its good to know how your engine works incase it goes wrong. and I realise that I would be better to be getting up to temperature.If the engine is 60 years old and the water system has been like that for 20 years or so. I thought the phrase would be"if its not broke dont fix it ? It would be terrible to put strain on some thing when its running so reliably. Or is a boat that is new to you ?
Click to expand...

I bought the boat in 2001 and live on her most of the year. What prompted me to look into this was that I would like to fit a calorifier. I'd not had a boat with what I thought was a raw water cooling system before. Thought it was an age thing, naive or what?

Got some sound advice from this forum and investigated.

Whats concerning me is the possibility of the block getting bunged up and hot spots developing which will cause damage. If it's possible I intend to reinstate the sealed system if only because I can use inhibitor to prevent internal corrosion and antifreeze for obvious reasons. The calorifier will be a bonus.
 
stuhaynes said:
I bought the boat in 2001 and live on her most of the year. What prompted me to look into this was that I would like to fit a calorifier. I'd not had a boat with what I thought was a raw water cooling system before. Thought it was an age thing, naive or what?

Got some sound advice from this forum and investigated.

Whats concerning me is the possibility of the block getting bunged up and hot spots developing which will cause damage. If it's possible I intend to reinstate the sealed system if only because I can use inhibitor to prevent internal corrosion and antifreeze for obvious reasons. The calorifier will be a bonus.
Click to expand...

well you have good intentions which makes sense .def' makes sense to find your way around it to see how/why its working. If you find a way to increase the working temp .if its possible to increase in stages 50/60 first and see how the engine reacts after a few hours/a good run .
but as i said I know nothing im sure you will get someone on here to help allready one or two ideas .
 
Freebee said:
I think a fundamental question is how are you measuring your quoted temps, have you a temp gauge? if so where is the sender fitted??
Click to expand...

Yes there is a temp guage with a sender unit in the head. As mentioned in previous posts I now know what the problem is. The boat has a freshwater sealed system that's cooled by salt water in the heat exchangers. For some reason the fresh side has been disabled, pump removed and salt pipework directed straight into the block.

I was lucky enough to be able to contact a previous owner, who had the boat from 1968 to 1990. He was extremely helpful. In 1990 the cooling system was definitely original and during the 'thousands of hours' he cruised her in those 22 years they ran the engine, on rivers, at 1600rpm at a resulting temperature of 160 degrees fahrenheit. He also told me that he was approached sometime early 90's by the buyer about an overheating problem, and advised him of what was required to fix it.

I think it's likely that the fresh water pumped failed and the owner couldn't get a replacement. The original pump was in fact 2 pumps, a circulating pump for the fresh water and a pressure pump for the cooling salt water. In any event the original pump is completely missing and has been replaced by a circulating ball type, but only connected to the salt side. To make this work the salt water side of the circuit has been diverted directly into the block. This explains, without doubt, why the engine is running so cold.

I'm now looking at the possibility of reinstating the fresh side via a new pump, possibly electric if I can't find a suitable mechanical one. At a push I may be able to use a central heating mains pump via the inverter if I can't get a 24 volt one to do the job.
 
Avoid an electric one if you can. A belt driven one would be easier to fit (Ford P-100 has one for example) It needs to be a centrifugal type as in cars, or you risk overpressurizing hoses etc before the thermostat opens. ( I quoted the Ford as it could be mounted separately, most cars fit them into the block or other housing)
A
 
DownWest said:
Avoid an electric one if you can. A belt driven one would be easier to fit (Ford P-100 has one for example) It needs to be a centrifugal type as in cars, or you risk overpressurizing hoses etc before the thermostat opens. ( I quoted the Ford as it could be mounted separately, most cars fit them into the block or other housing)
A
Click to expand...

Good thinking I hadn't thought of that, it also explains the design of the original pump (from the handbook), half circulatory the other half pressure for the salt side. Bu$$er to fit though.:rolleyes:

Actually, just had a thought. There is no thermostat and no provision for one so maybe the electric pump is still an option. What do you reckon?
 
Stu,
The idea of relying on an electric pump in a marine environent to keep the engine working does not appeal. I would rather hack something mechanical to fit. Adding a thermostat would be a good idea, esp if you are thinking of a calorifier. Back to motors, Renault use to fit thermostats in bulged hoses. This would avoid the housing problem. Come to think of it, the water pumps off the older Renaults would make good free standing pumps. Think the 4/5/6 series.
A
 
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