Trunkseal and Fuel Filler Compartment Drain (1800) Notes

First Published Jan 2020, R. Kwas, updates on-going

Result of Lack of Adequate Drainage Provision
Fuel Filler Compartment 1800 Drain



The svelte body and design of the 1800, does bring with it some special drainage issues...the clean rear bodywork has no vertical seams for water drainage.  Water collecting in the depression where trunkseal is located, as well as water collecting in the Fuel Filler Compartment 1800 Drain both need a way to escape, or else it will remain in a puddle, and grow mold, small water foliage, possibly primordial forms of life, but this is a sure recipe for rust.

Trunkseal Drainage: 

It seems there are variation of drain holes punched with fittings and drainhoses fitted and also no drain holes punched, but no drain hoses fitted from the factory...I am trying to compile the experience of owners of the various production years, to establish a correlation. 

Some of the subsequent pictures were supplied by V. Koskinen of the Finnish 1800 Club, and used with his kind permission.

Factory Drainage Provision:  

Trunk Lip of two (Green) present on Vesa '61 1800, when the British suppliers of the chassis were still on their best behavior as a subcontractors of Volvo.  See also P1800 chassis history

Drain openings (2) are typically obscured by the Trunk-gasket and so not immediately obvious (especially if no fitting or hose was installed below to further give away the location (like also on my '66!), but if present, they will be apparent at approx the lowest points on either side...look for a half-moon or 3/4" arc punched into the sheetmetal and only slightly deformed to present a drainage slot (it might be painted shut too).

Since my Trunkseal depression drain hoses were also not installed (no hose fittings in sight!), I made some copper hose-fittings and riveted them into place, below the Drainslots. 


Onto these, I installed 3/8* ID clear tubing to tie them into the Fuel-filler Depression drain-hose (thankfully present)!  I don't know why the factory never installed the drains on some later cars...maybe the Brits were already cutting corners in ~'65 or so, on their way to working themselves into bankruptcy...  The chassis of my '66 was still being supplied to Volvo by Jensen/Pressed Steel Cowley, but shortly after that, the contract was cancelled by Volvo, and production was moved to the Torslanda plant back in Sweden. See also: P1800 Chassis History

Drains can be added (or retrofitted if not present) to the seal surface, using the punched drain openings, and plumbing them to the existing Fuel Filler Compartment Drain tube.  J. Massey added some fittings and hose, and tied the drainage into the Fuel Filler Compartment Drainhose under Fuel Filler Compartment...a good solution, as simply allowing drainage to the panel below is asking for rust in the outer panel of the apron (see below!)...there are drainholes, but these are totally inadequate(!)...water would have to find its way to them, and not be captured by any sand's a very BAAAD situation!  Any sand or debris is perpetually damp and will cause the panel rust shown below.  

Pictures of J. Massey's drainage solution and used with his kind permission. 

Result of Lack of Adequate Drainage Provision: 

So where does any water (or a dropped Tank or Fuel-Sender Screw) go which is allowed to drain down the little slot between Trunk-floor and outer body skin?  In that horizontal ever-narrowing space, baing captured and held there by any debris, that's where!...what does the reader think that will result in...? 

View of inner panel, looking from under trunk, rearward (Tank removed, and round Tank corner of opening is visible).  To help with viewer's orientation, Trunk latch is white rectangular box in upper area of shot.  Water which is simply allowed to run down slot between outer body and Trunkfloor, is then in the space between the inner and outer panel...sure there are drainholes (Yellow), but water will be captured by any sand present in that narrow space and promote rust on both panels as apparent here!.  Pictures by Jean of the Volvoniacs Forum and International P1800 Owners Club ( ), and used with his kind permission.   

View from below and in back of the vehicle.  (Tank removed, Tank opening is visible)...result of moisture (likely wet sand between inner and outer panels)  is clearly visible. 

My response to a posting on this subject:

"If you are installing new panels and only have the half-moon punchouts, I strongly recommend adding fittings and draintubes, and routing these to the Fuel Filler Drain, and NOT to simply to between the outer and inner lower valance (as originally from the factory, if present at all!?!) where the moisture WILL WRECK HAVOC and cause rust (see pic!).

I agree with George, it's not a very good design, but fortunately, easily improved by simply rerouting the drains!

That yellow circled hole is where the water IS SUPPOSED to run out...YEAH RIGHT! and make nastys hole is what it really does instead..."


Fuel Filler Compartment 1800 (Carburetted) Drain:  

A Drainage provision was included for water entering the Fuel-filler Depression.

View of Fuel Filler Compartment with its Drainhose (Green) connected and routed through the Trunk-floor to the outside.
Also evident is the Fuel Tank Vent (Orange), which has a very different function.

Water in the Tank: 

It is crucial to keep the small drain opening in the Fuel Filler Compartment, free of debris which can block it, which would allow water to build up to a level high enough to flow into the Fuel-fill pipe!  That would be a failed attempt at water injection, and generally BAAAAD!  Check for and clear any debris at each fill-up! It doesn't take much to block the tiny drainhole! 

Vesa's nicely restored Fuel Filler Compartment.  Drain is below locking tab, location is shown in OrangeKeep this Drain Clean and Clear!

Why do Fuel tanks fill with rainwater?  Unfortunately, the Fill-pipe edge is lower than the Body overflow edge, so if normal path for drainage A  is blocked, and spring-loaded rubber seal on Fill-pipe opening is less than perfect, secondary drainge path B  is into Tank!!  This implementation having originated from a country known for rain...hmmm.

I don't know much, but I know water likes to run downhill...

This article is focused on water drainage, but recently, a question came up on the area of the Fuel Filler Compartment, concerning the rubber Tankseal and the (necessary!) tank venting.  Link to:  Correct 1800 Tankseal Installation allows Atmospheric Venting




Answer to Swedespeed Thread:  Trunk deck lid weatherstrip trough standing water - 1966 P1800S

"...if you look carefully, you should indeed find two drainage provisions at the low spot on each side...I have them on my 66!...they were halfmoon shaped, only partially punched deformations, and mostly sealed with paint, and both were somewhat hidden under the gasket, so not so obvious (until gasket was removed), and not very effective either!! On the back side of sheetmetal, they had nothing in the way of a drain tube attached, so any water which did make it through there, would essentially drip through there, and run down the back side of the (cardboard) panel in the trunk, draining out below that...and any remaining water, or water that didn't make it through the drains, just sat there growing algae or rust, until it as you note, evaporated away (an example of WAY less-than-impressive British automotive engineering, from a country known for rain even!)...

Like you, I didn't like this so much I made up some (copper) fittings to interface with these "drainholes" (which I opened a bit to assure drainage and flow), and plumbed them up using 1/2" ID clear hose I routed the drain hose (downhill obviously) over to the Fuel Filler drain (also 1/2" ID), and Tee"d it in there...this works great!...and no more standing rain-water, or water draining down inside panels..." International P1800 Owner's Club 


Reference Information: 

P1800 Chassis History according to Vesa:  "Assembly was moved from Jensen factory, West Bromwich to Sweden already at the beginning of 63. Only 6000 first ones were so called "Jensens". (1800S; S stands for Sweden made). Body parts kept coming from Scotland to Sweden though. (Pressed Steel Cowley)".


External material sources are attributed.  Otherwise, this article is Copyright © 2020.  Ronald Kwas.   The term Volvo is used for reference only.  I have no affiliation with this company other than to try to keep its products working for me, help other enthusiasts do the same, and also present my highly opinionated results of the use of their products here.  The information presented comes from my own experience and carefully considered opinion, and can be used (or not!), or ridiculed and laughed at, or worshipped, at the readers discretion.  As with any recipe, your results may vary, and you are, and will always be, in charge of your own knuckles, and future! 

You are welcome to use the information here in good health, and for your own non-commercial purposes, but if you reprint or otherwise republish this article, you must give credit to the author or link back to the SwEm site as the source.  If you donít, youíre just a lazy, scum sucking plagiarist, and the Boston Globe wants you!  As always, if you can supply corrections, or additional objective information or experience, I will always consider it, and consider working it into the next revision of this article...along with likely the unique metaphor and probably (likely) wise-a** comment. 


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