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Perkins Perama thermostat?


philthane

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I think this is 40 years old, vintage enough? My engine is a Perkins 100 series with a Perama Marine conversion, indirect cooling. On a sunny day going against the current on a river the engine temp gets to 70°C. On a canal going slower to about 40°C and on a cold day it barely rises off the bottom of the dial. I assumed either a thermostat stuck open, or missing. I have a downloaded copy of the manual and there appear to be two variants, one with the thermostat behind the water pump, one with it in a housing. I can't see a housing so I took the pump off and there's nowhere behind it to fit a thermostat. Am I being stupid? Or is it possible a previous owner has built a Franken-engine using parts from both types so there is no place for a thermostat?

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Are you sure the tempetature gauge is reasonably accurate? If so I would agree with your diagnosis but have no knowledge of the engine. Thermostats are usually found where the hot water outlet pipe leaves the cylinder head. 

If all else fails a bypass connection between the outlet and the inlet will help it warm up. Fit a full flow ball valve in it so you can vary the amount of flow in the bypass.

N

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I can't be sure the gauge is accurate without buying another to check it, but certainly moves from cold to warmer depending on how hard the engine is working and the ambient temp, so it seems to be a good indicator even if the figures are not quite right. The thermostat certainly isn't where you'd expect. ie where the 'top hose' leaves the engine - because there isn't a top hose on this model. The water from the cylinder head runs straight into the manifold/heat exchanger internally, no external pipes at all.

Latest advice from a Perkins dealer is that it's actually inside the heat exchanger body. I've looked for a way in but now I have an exploded diagram it seems that I have to remove the manifold/heat exchanger because the thermostat is fitted between the two. It makes sense in terms of the water flow, but is a pain to get at!

Plan B is to fit an electrically operated valve in the 'bottom hose' returning cooled water to the pump with an electronic thermostat and a probe into the heater take-off. Once I get the engine up to temp I plan to fit a DIY calorifer, but there's no point if the engine runs cold!

 

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Just a thought. At one time Renaults had the thermostat secured in the top hose by a jubilee clip. Any chance one could be fitted into the top skin tank hose (assuming a narrow boat). See https://www.eurocarparts.com/search/209745051?gclid=EAIaIQobChMIhaPH_ovY2QIV4ZPtCh0ATgkjEAQYASABEgLBRvD_BwE

It may well work in other places as long as you fit it the correct way round and if it does not have one drill a small hole in the valve disk. It will probably be a bit hot for typical boat use but as long a sit is a sealed cooling system it should be OK.

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An update for those interested. The thermostat is in the cylinder head behind the manifold/heat exchanger. The manifold is held by both studs and screws so it has to slide off. Well I've slid it about 15mm, far enough to see the edge of a thermostat, but it won't go further because it collides with the starter solenoid. Next job is to figure out how to remove the solenoid, or the whole starter, when the screws are hidden by the manifold! With a car starter you can often crawl under to reach the screws. Not an option with a boat. After all this I really hope the thermostat is faulty!

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