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Isuzu 35HP 4LB1 - Water hose replacement


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Hello everyone, Its been a very long time since I last posted, but I'm hoping you can help.

 

I've an Isuzu 35hp engine, model 4LB1 - which I've had for 15+ years now.

 

It's still using the original EPDM rubber hoses between the engine and skin tank for cooling, I'd like to swap those out to avoid failure due to the hoses getting brittle.

 

I've checked all over the existing hoses for the dimensions and found nothing - does anyone know what the internal diameter of the Isuzu water outlet/inlets are?

 

I've read through the service manuals, and whilst it tells you all the relevant info on disassembly - it makes no mention of the diameters!

 

I'm trying to get all the parts I need before getting to the boat, so as not to drag this out over several weekends, obviously I could just pull the existing pipe and measure, but that would dump all the coolant into the bilge, which I don't want to do (yet).

 

Edited by stuart
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If you don't get any direct answers you could try :

 

Measure the OD of the hose

Measure the wall thickness at the end of the hose (after the jubilee clip)

 

Take the OD minus 2x wall thickness to get the ID.

 

 

Or, if there a bit of spigot that hasn't got hose on it measure the OD with a pair of calipers and get a hose a 'fraction' smaller

Edited by Alan de Enfield
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I took the plunge and pulled the pipes off to measure as I couldn't find any information online.

 

Here's the results, in case it helps somebody else.

 

On the bottom of the header tank, is a 35mm outlet, requiring 35mm I/D hose

IMG_20210412_183101.jpg.cd5b7ace2024d602c9da2f8e4e4f293d.jpg

 

The other side of the pump is also a 35mm I/D hose (marked X below)

 

IMG_20210412_183044.jpg.a230f8582df2ac4f9e71de2f5c2ff034.jpg

 

 

 

On the thermostat to header tank connection, it's a 90 degree bend.  

A = 32mm outlet, requiring 32mm I/D hose

B = 72mm

C = 112mm

D = 100mm

 

IMG_20210412_183053.jpg.d989b9c9b21ae4274825b55955f1d3ad.jpg

 

The hot water take off for the calorifier is two 16mm barbed fittings.  Requires 16mm I/D hose.

IMG_20210412_185143.jpg.59c98a3d1a7c3eb147e893ce6e28e8db.jpg

Edited by stuart
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39 minutes ago, stuart said:

On the bottom of the header tank, is a 35mm outlet, requiring 35mm I/D hose

 

Ideally you should use a hose ID smaller than the diameter of the spigot, it should have slight expansion as you push it onto the spigot. If it is an 'exact' fit, or slightly loose when you compress it with your jubilee clip it it can 'bag' giving a leak path.

 

The reason for the 'christmas tree' (barbed) ridges to is achieve such expansion and the hose ID should be the dimension at the 'bottom' of the 'barbs' not the 'top'.

Edited by Alan de Enfield
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