Posted: Tue Jul 27, 2010 6:10pm

I have a narrow boat powered by a Ford 1800glx diesel engine and I have an overheating problem. With a thermostat fitted after 15/20mins at 600 revs the temp is 150c.Take the thermostat out and it runs at 80c but of course we have very little hot water for showers. We have tried drilling a hole in the thermostat and it still boils. As the gearbox is also water cooled and this gets very hot we have had to leave the thermostat out. We have taken out every available cooling pipe to check for a blockages and found nothing. Have you come across a similar situation and can you help? Thanks in anticipation Barrie.

Posted: Tue Jul 27, 2010 9:47pm

It has been known for the impeller to fall of the engine water pump spindle so its worth checking but if that was the case taking the thermostat out should not make much difference. I doubt it is an undersized skin tank because it happens so fast and at such low speed. I do not see how a temperature gauge graduated in Celsius could ever reach 150 unless you have boiled all the water away from the sender. 110 or 120 possibly, but not 150 - are you sure its not a Fahrenheit gauge? I note that you have not told me that you changed the thermostat. If you have not then that would be a good thing to do - especially if this started after overheating from another cause. It is also possible that the gauge and sender unit are not matched but if you are sure the engine boils and pours steam out then that will not be the issue. After you have satisfied yourself that the pump impeller is tightly fitted to the shaft, the thermostat is opening at the correct temperature and the engine is really boiling I fear you have a failed head gasket or a crack in the head of cylinder. Tony Brooks

Posted: Wed Jul 28, 2010 7:36pm

Hi Tony. Thanks for the prompt reply. Sorry about the Mix up between F and C. It is a brand new gauge and sender in Celsius. The water pump was checked last year and we fitted a new timing belt whilst in there. Forgive my ignorance as I dont know a lot about engines but If it was a cracked head or leaking gasket wouldnt I see contamination in the oil or leaking water? Thanks again, I dont think I have ever read a mag where you get such a fast replies to your problems.

Posted: Wed Jul 28, 2010 8:15pm

Well that suggests the gauge really does read 150C but I sill have difficulty believing it. The cooling system should be pressurised so the water will boil at rather more than 100C but I doubt the internal temperature would get to 150C until after the water around the sensor had boiled away and you would have stopped because of the steam clouds long before then I would have thought. However let let that one pass. There are several symptom of a blown head gasket and not all of them involve oil in the coolant or water in the oil - especially if the engine is running with good clean combustion. If the head gasket failure or crack is not in close proximity to either an oil passage or water gallery you may only get red/white hot combustion gasses leaking into the coolant. Now over a period they may start to build up some hydrocarbon liquid in the water but not at first. If the new gauge and sender came in the same box they should be fine but if they were supplied separately you may have an American standard sender paired with a European standard gauge and that will give odd readings. I am away on holiday at the moment so can not easily check which way the gauge would be out but I think it would read high. Tony Brooks

Posted: Fri Jul 30, 2010 8:14pm

Thanks for your help and advice. Barrie

Posted: Sat Jul 31, 2010 9:50am

Barrie, I have been pondering this since your first post because the symptoms seem a bit odd to me. The fast overheat at such low revs does not quit fit with the engine running at 80 without the thermostat. As you say you drilled a hole in the thermostat (I just hope it is in the valve disk or mounting flange and not into the wax capsule which would give the symptoms you describe) and you have checked the hose for blockages I assumed that you have a fair idea about what you are doing. However Just to be clear it is important that the cooling hoses from the engine to skin tank are straight, slightly uphill towards the engine runs with no up or down loops to trap air. It is also important that you bleed the air from the skintank several times after refilling the engine and running it. There should be a plug or tap at the top of the tank specifically for this. If the header tank is directly above the tank with an upward pipe run to it from the top of the tank it should self bleed. I have also assumed that this is a dry exhaust skin tank cooled boat and not a heat exchanger system. Tony Brooks

Posted: Mon Aug 02, 2010 6:01pm

Hi Tony, Over the weekend a friend loand me a laser thermometer (what a piece of kit!!!!) we ran the engine up to, temp guage 80c, BUT the thermometer couldnt find anything on the engine over 41c. I contacted the mechanic he had fitted a new gauge but left the old sender in (you had suggested this in one of your emails) we are now obtaining a new sender to fit but it looks as if the temp gauge is reading double the engine temp. I will keep you informed. Barrie

Posted: Mon Aug 02, 2010 6:06pm

I fear you may need an adaptor to fit a European sender into a Ford block and that may not be easy to obtain. My advice is to make the "engineer" provide an American standard gauge. Tony Brooks

Posted: Sun Apr 13, 2014 4:37pm

The exact same thing has just happened to us with our Perkins D3 Diesel. Just had the engine remounted, new shaft bearings and re-aligned. The header tank overflows when it overheats. We are having it looked at to-morrow. The phone diagnosis suggests it is either a line blockage or failed thermostat. Oil pressure us good and everything else is working normally.

Posted: Sun Apr 13, 2014 6:59pm

My diagnosis until proven otherwise is that you probably have an airlock in one of your main hoses or the skin tank has not been properly vented. However if thsi is NOT a skin tank cooled boat there are other things it could be. Tony Brooks

Posted: Wed Apr 16, 2014 8:23pm

Thank you. It turned out to be an airlock. The engineer who knew our engine worked told us what to do. The engine water cooler header tank had to be topped up as it was lower than it should have been and the header tank above the engine eventually returned to its normal level after having overflowed before. We have now travelled for a couple of days with no further problems.

Posted: Wed Apr 16, 2014 8:23pm

Thank you. It turned out to be an airlock. The engineer who knew our engine worked told us what to do. The engine water cooler header tank had to be topped up as it was lower than it should have been and the header tank above the engine eventually returned to its normal level after having overflowed before. We have now travelled for a couple of days with no further problems.

Posted: Wed Apr 16, 2014 8:23pm

Thank you. It turned out to be an airlock. The engineer who knew our engine worked told us what to do. The engine water cooler header tank had to be topped up as it was lower than it should have been and the header tank above the engine eventually returned to its normal level after having overflowed before. We have now travelled for a couple of days with no further problems.

Posted: Thu Apr 17, 2014 7:36am

Just for the record the reason the coolant overflows is because air expands far more than water when heated so it pushes the water out of the way. Often the initial overflow is of hot, not boiling water and that gives a clue to it being air. If your skin tank is fitted with a vent plug/screw it is always a good idea to vent it at least annually to prevent the tank filling with air/gas thereby reducing the cooling ability.