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AuthorMessage
psmullan
psmullan

Posted: Sat Sep 13, 2008 12:08pm

Post Subject: BMC 1500 Overheating

Hi I have a 60 foot narrowboat with a BMC 1500cc engine that is cooled by a slab tank. The engine is not connected to the hot water system. 2 years ago I had the engine stripped down and overhauled by Calcutt marine. My local boatyard re installed the engine into my boat for me. Since then the engine has overheated. If I run at cruising speed I can go for about 2 hours and then the guage will go up and the water starts emptying from the radiator cap overflow. If I go at a much slower cruising speed I can go for sometimes up to 5 hours before it starts again. I have had a new rad cap fitted, a new water pump and a new header tank. The pipe from the header tank down is only about a quater of an inch thick and I do intend to put a bigger pipe in. I have probably done about 500 cruising hours since my engine was re-conditioned, although the overheating started immediatley I had the engine installed. Before the re-conditioning the engine never overheated and the gauge used to get up to about 180 degrees normal running. As far as I know I do not have an air-lock and am totally baffled as is my local boat yard. I have to assume that the re-conditioning was carried out correctly? Please can you offer any advice Many thanks S Mullan

Tony-B
Tony-B

Posted: Sat Sep 13, 2008 6:19pm

Post Subject: BMC 1500 Overheating

Dear Mr Mullen, It comes down to air in system, probably in the skin tank or a blown head gasket although I have recently heard of a 1.5 where the water pump impeller had fallen off. I feel that Calcutt are unlikely to have dropped one with the head gasket, but it remains a possibility. I do not fully understand the relevance of the 1/4" hose because you should be able to fill the engine from the exhaust manifold cap. If the cap has no spring and valve under it simply use the header tank cap temporally. If your "slab tank" is a conventional vertical skin tank then it should have a vent tap or plug high up on it. Undo this and fill the engine until coolant flows, air free from the tank. If the tank's "top hose" runs up hill all the way to the engine so no air can be trapped then it may not have a vent. With the filler cap off run the engine at fast idle until the thermostat opens, you should see lots of water movement in the manifold (no significant movement and a hot engine means the water pump impeller needs looking at). You may well also find air bubbles out so top up as required. Refit the cap and have another go at the skin tank vent. If the problem persists and all the hoses between tank and engine are over 1 inch in diameter without kinks or crushes then your boatyard needs to talk to a local garage about borrowing some form of tester to check the head gasket. Once you have double checked there is no air lock in the system you could always phone Calcutt and get their advice, but it sounds like air to me.If the overhauled engine is producing more power or has a higher maximum speed set then it could be the usual undersized skin tank issue. For vertical tanks Beta advise about 1/4 sq ft per hp and my calculations say about 1/3. Your tank, for a BMC 1.5 should have an area of about 10 to 12 sq. ft. Tony Brooks

perardua
perardua

Posted: Thu May 12, 2011 10:49am

Post Subject: BMC 1500 Overheating

Hi, I have exactly the same problem with my BMC fitted to a yacht I purchased in Sept 2010. Did you manage to solve the problem?

Tony-B
Tony-B

Posted: Thu May 12, 2011 11:28am

Post Subject: BMC 1500 Overheating

Unless you have a steel yacht with skin tank cooling and dry exhaust (unlikely) then your problem is likely to be different from one on a canal boat. If you email a photo of your engine taken from the top with a clear view of whatever is on the front of the engine to Tony@TB-Training.co.uk I will try to identify the type of cooling system you have and then offer advice. If you know what type of cooling system is employed (Direct raw water, heat exchanger or keel cooling) plus the make & model of gearbox do not worry about a picture. Tony Brooks

Tony-B
Tony-B

Posted: Thu May 12, 2011 11:28am

Post Subject: BMC 1500 Overheating

Unless you have a steel yacht with skin tank cooling and dry exhaust (unlikely) then your problem is likely to be different from one on a canal boat. If you email a photo of your engine taken from the top with a clear view of whatever is on the front of the engine to Tony@TB-Training.co.uk I will try to identify the type of cooling system you have and then offer advice. If you know what type of cooling system is employed (Direct raw water, heat exchanger or keel cooling) plus the make & model of gearbox do not worry about a picture. Tony Brooks

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