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BMC1500 Head gasket repair person in Lancashire?


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Iv been a great fan of this forum and have lurked and read many helpful topics. I now have a problem with my engine I have now replaced 3 heat exchanger polar end caps in quick succession that split following the engine overheating. I have no leaks, I have hot water through the calorifier so presume the thermostat is working, no oil discolouration, I have bled the air using a tap on the top of the skin tank and with the rad cap off have seen the water moving so the pump appears to be working. Rad cap is 7psi.

i ran the boat back to its mooring with the cap off so no pressure and got myself a head gasket test kit that turned from blue to yellow showing exhaust gases present in the cooling system= head gasket leaking??

this is where I am at...

my local engine man has retired so can anyone direct me to a good engineer to help me?

in the meantime I am considering a can of head gasket sealer only for now and repair in the spring..good idea?

have I missed owt?



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I really would not put any type of HG sealant in a diesel of any type. Firstly it's very unlikely that a cheap one from Bars or Halfrauds will work if it has failed in a significant way, and secondly they have a nasty habit of sealing up a lot more than the HG, including the heat exchanger itself. 


First question, have you checked the engine oil for signs of anything other than normal black engine oil ??

If there is any trace of coffee cream mayo, change the engine oil, (You can leave the filter alone if you do not have one), before anyone tries to start the engine.


Second, what was the coolant or cooling system doing when the overheat alarm went off ??

Third, any nasty exhaust cloud result, or did it stay clear ??


Fourth, you say skin tank, so I presume this is a keel cooled version with a hot water only heat exchanger ??

It will not do any harm to remove the thermostat and if it's a normal suck and spit cooling system, definitely remove the thermostat, (Google how to test it in hot water).


Lastly, what exact type of test kit have you used ??

Some test kits will always show a positive result for old coolant. You might try sucking, (Use a pump not your mouth), some of the remaining coolant out to see if it has traces of engine oil in it.


At the present time I have no idea why the end caps blew apart, as they might just do that from a normal overheat that boils the coolant. Keep your fingers and toes crossed this is not a HG fault, but a simple overheat caused by a bad pump, kaput thermostat, blocked pipe, low coolant level, air in the system, or in the case of suck and spit systems, failed canal or sea water pump, or slipping belt. If it does suck in sea water, then also check the intake water filter and exact sea cock position. Never had a serious overheat on any engine I was responsible for, but have had to suddenly shut a few down for running a tad too warm for comfort.. One cos a daft plastic water filter had split, another cos we were partly aground in a rather muddy river, so the donkey had started to suck air in, and lastly cos the belt had been slipping due to some clumsy oaf spilling fresh engine oil over it. None of those 3 would have been possible with keel cooling.


If you do get forced into running an engine with a failing HG, change the coolant for pure water, (Keep the engine bay above freezing), as anti freeze is 100 times more problematic in terms of destroying the additives chemistry and causing direct metal to metal wear, than diesel in the oil, and 10 times worse than tap water.


Tony B will be along soon to let us all know why the ends caps split or blew wide open. 

  • Greenie 1
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Splitting Polar end caps is usually due to the radiator cap being too high rated. I always run them at 5 psi.

When you say caps, do you mean the hose connectors from the heat exchanger/exhaust manifold? I always fit extra hose clips around the smaller diameter to resist the stretching under pressure. There are also some poor quality non original Polar caps around.


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2 hours ago, Tracy D'arth said:

Splitting Polar end caps is usually due to the radiator cap being too high rated. I always run them at 5 psi.

When you say caps, do you mean the hose connectors from the heat exchanger/exhaust manifold? I always fit extra hose clips around the smaller diameter to resist the stretching under pressure. There are also some poor quality non original Polar caps around.


I have a Polar manifold and end caps are a ridiculous price. Bowman's are a couple of mm smaller but can be eased on with a little effort.

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You know of all the time I've spent in and around boats of every size, shape and condition, no one has mentioned an incident or issue with split Polar ends, I presume this donkey has a header tank for its skin tank ??

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10 hours ago, Tracy D'arth said:

Splitting Polar end caps is usually due to the radiator cap being too high rated. I always run them at 5 psi.

When you say caps, do you mean the hose connectors from the heat exchanger/exhaust manifold? I always fit extra hose clips around the smaller diameter to resist the stretching under pressure. There are also some poor quality non original Polar caps around.


Interesting, so the pressure needs to be kept as low as practical to reduce the risk of the far Eastern, or even near Eastern Polar caps splitting. If that metal pressure cap was connected to an expansion tank with a lower rated cap, as it is in most cases of both a suck and spit cooling system, or keel cooled cooling system, the main metal caps rating is only of interest if the expansion tank system blocked up, and that is very, very unlikely. I suppose there is a chance that this version of a BMC 1500 was not fitted with an expansion tank, in which case the caps pressure rating is going to be very important.


If you are fitting hoses that might be a bit Iffy in terms of them getting blown off during an over heating incident, then although I would question why the alarm did not activate at a lower temperature, (It should go off before there are consequences), I would use a hose material that has a higher pressure rating, and use the type of clips that are designed for that type of hose. If you can't afford to do that, because your specialist hose company, (Look for a company that stocks hydraulic hoses in addition to normal fuel and water hoses, along with all of the different clips, as they will be able to help supply a suitable hose), fit the best quality hoses available and buy threaded machine screw type of hose clamps, (TB will know the correct name for that type), or failing that type being available, genuine certified Jubilee clips that are not some type of cheaper copy. Then clean off the pipe the hose is fitted to and wire brush, (40 or 60 grit standard with a flappy wheel if possible), it to take off the shine if it is stainless or alloy. If it's steel, use a rotary wire brush until all traces of rust have gone. Then smear it with a Sabatack 750XL, or equivalent flexible marine adhesive that sticks to metals and has a serious test approval listed, BUT make sure that you do not use too much by wiping it with a cloth to leave a very fine layer. Then as Tracy suggested use 2 of your best clips to fit a slightly under size hose that needs a lot of pressure to push onto the pipe. 


OFF TOPIC, but fire safety related.

  The final result of the procedure I described above, will be a hose that is nearly as good as a hydraulic one with pressed fittings, I did just that for an adjustable end nozzle for my Amerex fire extinguisher, and that is rated at 96 PSI Max, with a normal rating of 70 PSI if you only pump it up to the bottom of the green arc. It did not blow the brass nozzle off the hose end when I tested it by pressing the discharge lever down with the nozzle screwed shut. I only had room for one real Jubilee clip and the nozzle end should always be left in the fine spray position, (Fully open), which is the position it should be in for most fire fighting tasks, and definitely the one for a diesel fuel fire if it's loaded with water. You can recharge a stainless steel Amerex using a real good car foot pump. The twin barrel Halfrauds one I have does the job, but I do need to really jump on it to get the pressure into the green arc, obviously using a truck stop or good garage tyre pressure line is far quicker.

  The US made Amerex is still in production, and no one will ever make a better portable and easily rechargeable at home type of fire extinguisher. They cost about 150 quid or so, and there is an import dealer in the UK. I got lucky in Fleabay and found one that is 30 years old for 15 quid, plus a return ticket to Weymouth.

Model 240 Water Extinguisher | Amerex Fire (amerex-fire.com)

Do not make the mistake of buying a real good copy, and there is no mention of the new version being rechargeable at home. Not sure why, but if you want to buy this model, I would recommend downloading the service manual to see if it can be recharged or not. I can't tell from the pictures or description if this is the same as the classic model that is very popular with older fire fighters for use at home. 

  Make sure you understand the difference between fighting a fuel related fire and a pool fire, as a fine water spray is no good for fuel or oil pool fires. So do not use it to put out a chip pan fire! A damp small towel works far better, if you don't have a fire blanket.


Edited by TNLI
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Pity late edits are verboten, but just wanted to say that I'm very pleased that my very old BMC 1500 does not have any Polar caps, not even a simple single one. Oddly enough some local yokel who seems to know about all the old time donkeys, said some time ago that I had purchased a good version, BUT he did not say why. I asked him again yesterday, and he said the cooling system was nothing but trouble if it had a heat exchanger. I presume he meant that parts like the Polar caps, belt driven sea water pumps, water filters, cooling water intake grills and sea cocks, thermostats and heat exchangers can complicate the maintenance schedule, or simply ruin a cruise down an old ditch by failing.


  I don't like thermostats and they can cause real trouble if they fail, (Fairly rare), or don't close or open fully, (Common if you use tap water), If one does not close correctly, it can result in the engine coolant temperature being rather on the low side during the winter cruise. That type of fault will make the low power related Carbon deposits issue worse, BUT one way of preventing or even reducing that nasty side effect old diesels all seem to suffer from, is to increase the low cylinder head temperature a tad or three. So I'm planning on adjusting my coolant temperature by using a Y valve diverter, (Don't know correct name), So when cold starting it will just send the coolant directly back to the intake hose, until I see the temperature is starting to rise enough to allow coolant to circulate through the skin tank. In other words I should be able to adjust the engines temperature. 

  Obviously I will need to position that Y valve so that it is clearly visible, along with a small red night light and warning notice. The oil temperature lags the coolant temperature in most engines, so you should try not to use anything more than high idle RPM until the coolant reaches normal operating range. Oddly enough the actual oil temp in many diesels lags by around 10 minutes, so full chat should not be used until that time. 



  If you really want to chew up the rings, liners, big and little ends, just try a winter time cold start with the throttle too far open, the sudden surge in RPM is one big source of wear metals, (Mostly Iron, Lead and Copper in the used oil analysis). The other common engine killer occurs whilst at anchor or on a mooring during a storm. The good book says the vessel should be manned with sufficient crew to weigh anchor and motor to a safer location, which does seem to be done correctly in most cases, but the crew fail to read the next chapter about making sure the main engine is available for a crash start, (Start it and full chat before crashing into something expensive), or coking up at idle all night. My plan is to fit a Wolverine sump heater and leave it on all night. That might result in me running the generator for an extra half hour, and the sump pad would need to be switched on a few hours after the engine was run, to make sure the top end was warm enough for full chat. 

Edited by TNLI
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14 hours ago, sunny said:

Bill bannister mousney road bamber bridge Bannister Engines or Wier street engineering blackburn

Business Contact

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Phone:  01772 338970


UNIT 1A, Hecla Works, Mounsey Rd, Bamber Bridge, Preston PR5 6LS, UK
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Business Description

Bannister is located in Preston, Lancashire. This business is working in the following industry: Car repair.

Name: Bannister

Engaged in: Car repair

Employees: 25-49

Sector:  Automotive »  Car repair

Industry: Maintenance and repair of motor vehicles

ISIC Codes  4520

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