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Thread: Heater water hose connection to 2.25 petrol engine

  1. #1
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    Heater water hose connection to 2.25 petrol engine

    Hi All,

    i was recently given a smiths heater, but I have no idea how the water pipes would connect to the engine. Are there a couple of blanked off connections on the engine head/block ? Do I need buy any kind of fitting to screw into the engine ? if so what are the part numbers ?

    Any guidance / pictures appreciated.

    Thanks
    John

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    There are two plugs which need to be replaced with pipe fittings onto which half inch (internal diameter) heater hose will fit. The one where the hot water comes out of the motor is between the two rear head bolts (of nine) on the left side of the rocker cover. The other where water returns to the engine is in the top of the housing that is bolted to the right side of the thermostat housing with the bypass hose from the water pump connected to the bottom. Worth noting that the plug where water temp sensor is fitted is on right side of front of head under thermostat housing.

    The threads on these are three eighths British Standard Pipe ie common water pipe thread in many countries including Australia. Note the size description is the approximate bore of the pipe, not the larger diameter with threads of which size is critical. Nineteen threads per inch. (American NPT threads around similar size have 18 TPI)

    The setup for the Land Rover optional heater on Series 2's is with an on off tap on the head with the control knob on top and the outlet at a right angle which reduces the length and amount of bending necessary in the heater hose. Worth checking that any heater tap allows full flow of water. I discarded one of the type that cable control can be connected to that was installed between hoses on my S2 because when full open it was obviously a significant flow restrictor.

    Worth noting that on the 300Tdi motors in Disco 1's and Defenders, with a somewhat similar setup with water going to the heater from the rear of the cylinder head and returning to the front of the motor, there is no heater tap. Seems the heater circuit is regarded as an important aspect of the cooling system to remove heat from the rear of the motor. Note that some cars have fancy heater taps that allow water flow to continue but bypass the heater element when heat in the cab is not wanted. I installed a bypass tap on my Series 2 that can be turned on in summer while the heater tap is off for the same result..

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    Another point worth mentioning is that the heater hose fittings supplied by manufacturers are often made of steel, Probably a penny pinching exercise by company accountants to save money. Are much more prone than brass ones to corrode. Most likely appropriate fittings are more likely to be available in brass at plumbers suppliers though. Probably best when you try to obtain fittings, take one of the plugs from your motor to check the threads are the same.

  4. #4
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    Series 1-2a engines have a screw valve on the top of the head, S3 have a remote operated valve.

    Earlier engines have most of the distance copper pipe, with only short sections of hose, but it works with all hose.

    I remember the plug size as 1/2" not 3/8", but I could be wrong - I just got the bits that fitted out of my collection of pipe fittings!
    John

    JDNSW
    1986 110 County 3.9 diesel
    1970 2a 109 2.25 petrol

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    Quote Originally Posted by JDNSW View Post
    Series 1-2a engines have a screw valve on the top of the head, S3 have a remote operated valve.

    Earlier engines have most of the distance copper pipe, with only short sections of hose, but it works with all hose.

    I remember the plug size as 1/2" not 3/8", but I could be wrong - I just got the bits that fitted out of my collection of pipe fittings!
    Your recall would have been thinking something like in terms of bolt sizes. Diameter of the threaded bit of 3/8" BSP is very slightly larger than that of 5/8" and M16 bolts. Remember British Standard Pipe nominal sizes describe the approximate bore of the pipe, which can vary. Is smaller with thick walled steam pipe. Note with metrication BSP pipe sizes are now often described with the rough metric bore size in millimetres followed by "NB" for nominal bore . eg 3/8" equals 10 NB, 1/2" equals 13NB . 3/4" equals 19 or 20 NB etc.

    Standard plug size in these LR motors is 3/8 BSP . However, where they fit in for the two on my petrol Series 2 and the one in the same place in the rear of the head on 300Tdi in Defender, I have bored and tapped them to 1/2" BSP Allows increased flow for 3/4" copper pipe and /or heater hose. One of the steps necessary to improve mediocre heater performance. Can cater for bigger heater element or an additional smaller heater.

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    That's great information. Just to confirm my understanding...

    1. I need a couple of male 3/8" BSP threaded (19 TPI) pipe adapters to connect to.

    2. Adding the heater pipes as per your information above means that the coolant water will flow through the heater pipes, i.e. it's not a parallel water circuit that can be blocked off, otherwise the engine coolant won't flow - true ?

    Thanks
    John

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    JDNSW's Avatar
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    No, on the 2.25 engine it is parallel and can be turned off - and is in the standard installations. The 200Tdi (and later) requires it to be open.
    John

    JDNSW
    1986 110 County 3.9 diesel
    1970 2a 109 2.25 petrol

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    Thanks John, much appreciated.

    Cheers
    John

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