Water on the Floor, Notes
Dec 2019 R. Kwas, Revision ongoing,  [Comments added]

Heater Airbox
Reference Info


Leaks of fluids from a vehicle are seldomly a good thing, but when they occur inside the passenger compartment, and anoint the floor with liquid, the situation calls for some immediate attention!

Source should be determined first, and this will determine the urgency which which repairs might be necessary...at the low end of the urgency scale would be:

1.  ...leaks of exterior rain/washing (uncolored, possibly sudsy) water making its way past window seals (including Windshield) which are not working their best any more.  Next would be: 
2.  ...also uncolored, rainwater which has made its way into the fresh-air intake cowl in front of Windshield, and is somehow making it onto the cabin floor rather than being allowed to drain harmlessly away, and finally third (highest sense of urgency):
3.  green colored Water/Coolant, on the passenger floor. 


Condition 1.  Leaks of exterior rain/washing water by way of window seals: 



Condition 2  Leaks of uncolored, rainwater entering not by way of the weather seals at glazing, but from under the Heater Enclosure (and not Heater Control Valve!), considered: 

Rainwater which falls into the fresh air Vent in front of Windshield, is supposed to drain away through fitting located at bottom of Airbox / Heater Core Enclosure, shown below, to which a drainage hose is connected and routed away at firewall in engine compartment (next to Ignition Coil).  Sometimes, this drain is compromised by biomass which has also found its way into the fresh air intake through its grill.  The simplest way to proceed is to first inspect, and verify if such a blockage is the cause.  Because debris is cumulative, and depending on how many trees the car has been parked under in its lifetime, this is a good periodic maintenance operation.  Remove the Blower Assembly from the Air Box in the engine compartment to get access (do this with care to avoid damaging the plastic air impeller, which is undoubtedly brittle after so many years.  Inspect impeller once Blower Assembly is removed, and lubricate motor bushing.  See Reference Info below), and inspect for biodebris on top of Heater Core and in the area of fitting.  Clear/vacuum any blockage debris (the shop-vacuum hose, modified with a flexible rubber hose extension will help!).

Drainage fitting can be seen below, on a stand-alone Airbox / Heater Core Enclosure (so from the firewall side), is this first line of drainage defense. 

Some of the following pictures are by Derek of the VOC Forum, and used with his kind permission. 

(Viewed from passenger compartment side!) 
highlights Airbox rainwater drainage fitting.
(Viewed from engine compartment side [LHD]!) 


If this rainwater drain is blocked and not allowing drainage to be routed away through hose in engine compartment, water level will rise to make its way into the second chamber of the enclosure, where Heater Core is located, down through/past Heater Core, and to the lowest point in the Enclosure, where it will drain out the drain intended for leakage from an incontinent Heater Core. This is a second line of drainage defense.  This second drain hose, routes drainage through a hole in the transmission tunnel to under the vehicle, as seen below.  If this second drainage provision is clogged or otherwise compromised (for instance by some well-meaning individual installing a carpet without realizing they dislocated it from its hole, or even removed that hose totally in the process of installing the carpeting), or even if this tiny hose is overwhelmed by a rain deluge (reader will note that rain Drainage Hose is a lot larger than Heater Core Drainage Hose!), water can/will make its way to the driver and/or passenger floor areas.  

Below are pictures of this second drainage provision in the Heater Core Enclosure, as well as likely results of it not working as intended.  Rust in bottom of enclosure suggests rainwater drainage was impaired (pooled Coolant would have the telltale green color and likely not have rusted as it contains anti-corrosives), allowing standing rainwater to pool, and rust the inside of enclosure, likely also spilling over onto the cabin floor as it reached the level of air vent (oval opening), as it appears to have done. 


Heater Enclosure, with short drainage hose installed at Yellow



Location of drainage hole in transmission tunnel at Yellow.  Heater Control Valve, another source of leaks into passenger compartment, this time Coolant, at Orange (see Condition 3 below!).



The critical part in question, actually consists of two components...the rubber hose (PN 661063, which can be installed with Enclosure in place), and a barbed insert, which expands the OD of the hose slightly, but definitely, to assure a water-tight seal with the Heater Enclosure.  Unfortunately, installation of the securing barbed insert, must be made with access to inside of enclosure. 



Heater Airbox:  


A nicely refurbished Heater Airbox with fitting and retaining insert installed. 



Condition 3  Leakage from an incontinent Heater Control Valve is handled separately under the HCV.  Link:  https://www.sw-em.com/Heater_Control_Valve.htm  


Link to thread:  Water ingress via heater airbox:  https://www.volvoforums.org.uk/showthread.php?t=300775 (with many more useful pictures, including of the soft mounted Heater Core. While the original soft mounting foam is likely deteriorated at this point, Derek shows some nice alternatives for soft-mounting the thin and vibration-wear-susceptible(!) HC)  The foam also prevents air from bypassing the HC and so assures a maximum temp exchange:

Heater Core, well protected from vibration damage by a foam wrap, and ready for Enclosure to be buttoned up.  


Reference Info:

The Blower Motor of the Heater / Defrost System has a plastic impeller which is subject to breakage if the old, brittle plastic is mishandled (even only slightly!).  Motor can also develop noise or howling, or be sluggish to start as bushings dry and wear.  The Blower Assembly needs to be removed for access and although the bushing hidden behind impeller is difficult to access, applying lube with a snoozle will quiet this down effectively. 


Externally sourced material is attributed. This information is Copyright © 2019-2023.  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 odd metaphor and probably wise-a** comment. 


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