Perkins prima. (Montego/rover engine. )

[Tony Brooks]

25 minutes ago, Kingdom Isambard Brunel said:

This is another Perkins engine where a water leak from the internally mounted pump wrecks the engine as the antifreeze and water get into the oil. I remember a tractor engine where this happened and it had to have a total rebuild.

Its a crazy way of constructing an engine in my view.

I could see that the V belt ran the pump but to get at it means removing all the front cover.

 

There should be no oil behind the timing cover, those timing belts need to run dry - they are not the Ford type oil covered cam belts. The timing cover is not sealed to the block/front plate, so any coolant leak would just leak out at the bottom of the cover..

 

I can see no way a water leak from the water pump can get into the lubrication system on this engine. However, the water and antifreeze may well contaminate the belt and cause it to fail, leading to an engine rebuild, but that has nothing to do with coolant getting into the oil.

[Danzy]

3 hours ago, Bod said:

It is clear from the above post that the belt in your photo is the water pump drive belt (fan belt in old terms)

This will have to be removed, along with the cam Timing belt, under the yellow cover. 
To prevent major engine damage,

”Timing pins” have to be placed in the engine to prevent any and all movement in the cam shaft and crankshaft before the timing belt is touched. 
A simple service job, if you have the tools and knowledge!

If I recall correctly, it’s the screws that hold the water pump in place can be”difficult!!” to remove. 

As a matter of course, replace the timing belt, it has a limited service life, failure of the belt will destroy the engine. 
 

Bod

👍

[andrewbridget]

Hello. 

It's been a few weeks, so I've had mechanics round and they have taken the water pump off and apparently it's in good working order. 🤷.

But the problem persists. Water flow is not going through the skin tank. 

The whole system has been flushed and checked, the thermostat has been changed . 

The engineer mentioned that it could be a head gasket issue, but why would that affect the water flow around the engine? 

I'm flummoxed 😂. 

[Tony Brooks]

14 minutes ago, andrewbridget said:

Hello. 

It's been a few weeks, so I've had mechanics round and they have taken the water pump off and apparently it's in good working order. 🤷.

But the problem persists. Water flow is not going through the skin tank. 

The whole system has been flushed and checked, the thermostat has been changed . 

The engineer mentioned that it could be a head gasket issue, but why would that affect the water flow around the engine? 

I'm flummoxed 😂. 

 

Long shot. You say that you have the manual. Check what type of thermostat it uses. If it needs a bypass stat and someone has fitted a normal one, then a lot of coolant could flow back into the engine rather than through the skin tank.

 

A bypass thermostat is one that has a large "washer" hanging down below it. There is another type but doubt it would be used in that engine.

 

Just checked, according to Mr Google the Prima does use a bypass thermostat.

 

 

Edited June 4, 2025 by Tony Brooks

[andrewbridget]

It doesn't mention anything about it being a bypass thermostat. It just says it has a jiggle pin. 🤷

[Tony Brooks]

6 minutes ago, andrewbridget said:

It doesn't mention anything about it being a bypass thermostat. It just says it has a jiggle pin. 🤷

 

The photos on Google, including the ASAP listing clearly shows it is a bypass stat, without a manual I have no other way of checking.

 

Misnaming a Perkins Perama or using its manual that does seem to use an ordinary (non-bypass) stat it would explain the discrepancy.

 

If you take the thermostat out I expect you will see a largish hole in the bottom of the housing with an up stand around it which the "washer" seals as the coolant heats up. If it is not there, then an ordinary stat would be fine, but if it is, then that hole will allow hot coolant to pas staright back into the engine.

Edited June 4, 2025 by Tony Brooks

[andrewbridget]

Ok I'll look into it. This is the 2nd stat fitted . It does open at about 75°. It flows down the pipe into the skin tank then it just stays hot where the inlet pipe is attached. The rest of the tank is cool. 

[Tony Brooks]

1 minute ago, andrewbridget said:

Ok I'll look into it. This is the 2nd stat fitted . It does open at about 75°. It flows down the pipe into the skin tank then it just stays hot where the inlet pipe is attached. The rest of the tank is cool. 

 

The vertical skin tanks should have a temperature gradient from inlet to outlet, the outlet should be cool. I would expect something similar on a horizontal tank.

 

Assuming a typical vertical tank, where is the inlet and outlet? I would normally expect the hot inlet to be at the top and the cold outlet at the bottom, but some people reverse then, but that makes the pump fight the natural thermos syphon circulation, instead of enhancing it.

This screenshot from the manual clearly shows a bypass thermostat - you can see the washer like thing hanging below it.

 

 

[andrewbridget]

Ok I'll look into it. This is the 2nd stat fitted . It does open at about 75°. It flows down the pipe into the skin tank then it just stays hot where the inlet pipe is attached. The rest of the tank is cool. 

 

Thank you. I'll look into it. I have kept the old stat with the jiggle pin as finding it was challenging. I'll test it in hot water to see if it's still workable. 

[Tony Brooks]

24 minutes ago, andrewbridget said:

Ok I'll look into it. This is the 2nd stat fitted . It does open at about 75°. It flows down the pipe into the skin tank then it just stays hot where the inlet pipe is attached. The rest of the tank is cool. 

 

Thank you. I'll look into it. I have kept the old stat with the jiggle pin as finding it was challenging. I'll test it in hot water to see if it's still workable. 

 

The jiggle pin is only to allow air out as you fill the system, and as thermostat valves are rarely total water/airtight, I doubt it is vital. Many thermostats just have a small hole in the flange.

 

If the old thermostat does not have that "washer" appendage, it is not the correct one.

 

As long as the skin tank has adequate area you could fit an 82 degree or even, at a push, 88 degree thermostat, but if you have a calorifier it would make the domestic water dangerously hot unless you have a thermostatic mixing valve.

 

Edited June 4, 2025 by Tony Brooks

[andrewbridget]

For those all helped me resolve my issue (and I finally have). 

I d just like to thank for all the input received. I also learnt a few things along the way which I very much appreciate. 

So. I had a spare coil connection on my calorifier. I linked the coolant pipework to both with 15mm T pieces. 

Hey presto the hot water now heats up. The bottom one is still cold at the bottom exit so I believe that the calorifier is full of limescale. 

Which apparently can affect the flow and cause many other issues. 

So at my earliest convenience I will attempt to flush it out. If not it will be replaced. 

Thanks again.