Heater hose repair

Whilst I was struggling with replacing the pedal box I came across this obvious leakage around one of the heater hoses. I can't leave this because I don't want any new carpets ruined so I will need to investigate.

Heater hoses seen from under the dashboard and behind the LHS drivers knee pad. The heater ducting is visible to the right and the two water hoses are centre; one above the other. The lower hose in the picture is the heater bottom elbow hose and connects to the the bottom of the heater matrix. Two jubilee clips are visible; one on the bottom of the short matrix elbow and the other on the top of the long elbow hose that penetrates to the engine compartment. 

The upper hose in the picture  connects to the water control valve, although this wasn't leaking there are clear signs of  rusty leakage from the lower hose into the hardura soundproofing.

The hose concerned is the lower heater matrix hose. This is a three part hose that joins the heater matrix to the water pump. The first of these three parts is a short elbow that connects to the lower heater matrix spigot. This hose in turn joins to a longer elbow hose that penetrates the body through a grommet to emerge in the underside of the transmission tunnel. From here it runs forward to join with the final (straight) hose in the engine compartment and which connects to the water pump. These three hoses thus have two junctions and both are reinforced with metal (16mm OD) joiners.  For some reason these joiners are made of mild steel tube- not even seamless! This seems an odd choice for a high-end car since they will inevitably corrode.  I have already replaced the joiner in the engine compartment with a new aluminium equivalent and it now looks like I need to replace this second joiner under the dash although access is much more limited. This joiner is 76mm long, (16mm OD); it is inserted into both hoses and actually passes through the grommet in order to strengthen this joint and prevent vibration damage.

The Hardura insulation was stuck to the transmission tunnel so I eased it away using a wallpaper scraper so I could get at the hose, then, before trying to separate them, I drained the heater (and probably some of the head too) by detaching the heater to pump hose in the engine compartment at the joiner I had replaced earlier.

Heater hose joiner in engine compartment. These hoses have always seemed a little short and you can see that this one is tight up against the dipstick and block.  I will try to lengthen and re-route them when refitting. In the meantime I just detached the hose here...

...and let it drain. Detaching here meant that I could catch much of the coolant in a tray for reuse.

Access to the hose under the dash is (of course) limited. It  was worse in this case as the jubilee clip was corroded and it was a close run thing between the clip unscrewing or the screw head cracking off. Luckily the screw turned and I was able to release the clip. Although I could access both the jubilee clips on the joining piece, there was no room to swivel the hose off the joiner and to make room I had to remove the top of the elbow hose from the heater matrix. Access to this was impossible from below but since I had already removed the instrument pod I found I could reach it through this.

View of heater hose connections from underneath the raised dash pod. The orange component is the water control valve and associated cables- this gets in the way of accessing the other lower heater matrix elbow hose. The jubilee clip at the top of this lower elbow is just visible in the extreme bottom left of the frame formed by removing the instrument pod where the lower hose enters the bottom of the heater matrix. It could be unscrewed through the binnacle- I will see if this can be better positioned on refitting.

I was able to unscrew the jubilee clip at the end of the elbow hose where it attaches to the lower inlet of the heater matrix. The hose could then be levered back off the matrix spigot. Once this end of the hose was free it was possible to rotate the hose and so work it gradually off the joiner until the elbow hose was free.

Elbow hose released.

This left the top of the longer elbow hose (eventually to water pump) exposed with the joiner sticking out of it..

Corroded joiner still in position in lower elbow hose.

The joiner could be gradually worked loose using a screwdriver to break the adhesion between hose and joiner. Eventually this joiner also came free.

Joiner section removed- heavily corroded.

For some reason these joiners (of which there were two in this hose) are made of mild steel; which seems an odd choice for a high end car. I have already replaced one and will replace this one too with aluminium.

Long elbow hose still in position penetrating through the grommet. Rusty deposits are visible inside.

 Both hoses were clearly still dirty; they were quite crunchy when squeezed and seemed to have rusty deposits inside. The smaller hose was removed and rinsed through after squeezing to break off the deposits.

I didn't think it was likely that I could replace the long elbow hose easily (or even at all) since access up the transmission tunnel from underneath is very awkward and the fit through the grommet is tight. I did my best to clean out the pipe in position by squeezing it to break off deposits and brushing it through with a bottle brush to dislodge what I could. I want these hoses to seal onto the new joiner and rusty scale on the inside would prevent this.

While I was under the dashboard I did notice these two free wire connections: One is a double female bullet receiver connecting to two yellow and green wires, the second is a single male bullet connected through what looks like a suppression condensor. I don't know what these are supposed to serve but I suspect its something to do with long vanished audio equipment and presumably the screw holes in the centre console that I have had to repair. I will have to check, but in my earlier investigations I didn't find anything that wasn't receiving power so I'm hoping these are functionless.

Longer condensor wire- suppressor?

Condensor wire again but second female bullet on 2 yellow/green wires also visible.

Investigation shows that YG wires are used for Heater fans, ACU, Radio and otter switch. I know that the radio works and I don't have an ACU. Otter switch function is unknown but as I recall shorting the switch does now allow the fan to operate so I think that connection must be OK. I can't remember if I have ever tested the heater fans. The fact that this appears to be a junction of 2 YG wires does suggest that it could be from the two heater fans which both feed into a single fuse (no 17). However, this is not how the wiring is drawn in the diagrams. I will test and hope that the heater fans work- in which case I can assume that this contact is for the ACU and so not required.

I ordered a new aluminium hose joiner 80 mm long from Merlin Motorsport. It arrived promptly.

New vs old. Aluminium hose joiner 80mm seamless tube

Fitting was relatively straightforward once you have wriggled into position. I used corrosion block grease on the joiner to help it slip into the hoses and then fixed it in place with new jubilee clips. Since these clips are always going to be awkward I can't really risk them rusting again so I worked copper anti-seize grease into their threads before fitting. They were positioned for screw-head access from the foot-well with care that the clip bodies can't contact and chafe the other heater hose.

Heater hose re-fitted- all screws angled for access from foot-well; gaps ensured between clips and the second heater hose.

Finally I used some spray lube on the cable connections at the water control valve as this hasn't been used for a long time and may well be stiff.
I will also fit a little extra heater hose in the engine compartment as I'm not happy with the hose routing it was very tight on the dipstick and block and doesn't really fit into the hose retainer on the timing belt guard.

Lower heater hose routing- hose runs tight over the solenoid of the starter and immediately below the breather hose which will connect to the air box when its fitted.

I re-routed the hose sightly higher- I think this is better but it now has opportunity to rub on the solenoid and will probably be squashed against the air box breather when that's fitted- so I'm still not totally happy with it.