Farm Equipment - Why did they add the bypass hose on the WD-45?

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Why did they add the bypass hose on the WD-45?

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=165686
Printed Date: 16 Dec 2025 at 2:49pm
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Topic: Why did they add the bypass hose on the WD-45?

Posted By: garden_guy
Subject: Why did they add the bypass hose on the WD-45?
Date Posted: 08 Nov 2019 at 9:14pm

How come at some point between the WD and the WD-45, they added a small bypass hose from the thermostat housing to the top of the water pump?

I have a '53 WD (curved shifter model but still a WD) and it has the older style without this bypass hose. When did it get added and why?

Replies:

Posted By: DrAllis
Date Posted: 08 Nov 2019 at 9:38pm

Bypass hose was to allow more even warm-up of a cold engine, as it kept the water moving around thru the block and cylinder head until the thermostat opened. While the late WD's had the tall cylinder head and the newer thermostat housing, it doesn't appear the bypass hose was ever factory installed on any WD, only the WD-45's.

Posted By: garden_guy
Date Posted: 09 Nov 2019 at 10:32am

Makes sense. Thanks for the info!