Proactively doing a MGF heater hoses & pipes replacement project will be a wise preventative maintenance activity. This article covers replacing many of the hoses and specifically includes the five hoses associated with the interior heater circuit. This is by Mark Jones as published in The MG Driver magazine and elsewhere.
Background #
How do you tell if a hose is worn out? The most obvious sign is if you can see cracks or signs of swelling. But the look of a hose is not always a good indication of the condition of the hose. Hoses also weaken from the inside. If you see coolant oozing out from the end of the hose that it is a good indication that the hose is worn out. You can also squeeze the hose 2 to 4 inches from the end. If the interior of the hose has weakened, you should feel gaps inside of the hose.
As part of my research, I found only one mention of another F enthusiast attempting to replace the heater hoses and pipes. This is from the three MGF-specific forums. I found no information in the Workshop manual on the topic, aside from replacing the heater valve. The Workshop manual for the heater side of the engine coolant system is misleading in terms of the representation of the heater pipes. So, I modified the existing drawing to more accurately depict everything. The hoses and pipes with a table of part numbers and descriptions.
From the factory, all the hoses are fastened to pipes using constant tension band clamps. This type of clamp is superior to screw-tension hose clamp because constant tension band clamps are self-tensioning. The coolant pipes expand and contract with temperature. A constant tension band clamp adjusts to the expansion and contraction while maintaining a constant clamping tension on the hose.
Whereas, with hose clamps, you should go around and re-tighten the hose clamp after a couple of heat cycles. This is especially true with stainless steel pipes which expand more with temperature than mild steel pipes. It is also very easy to over-tighten a hose clamp, which damages the hose. On both of our MGFs, the hoses that connected to the underfloor pipes had the original constant tension band clamps replaced with hose clamps. I took this opportunity to replace all hose clamps with the constant tension band clamps. BelMetric has an excellent selection of constant tension band clamps.
Tools #
The only special tool you will need is constant tension band clamp pliers. There are two types available: plier-type and cable-clamp. I have found both to be of use. The cable-clamp type is very handy for reaching awkwardly positioned clamps and poor accessibility clamps. I have tried several different types of the plier-type. Some are better quality than others. Specifically in terms of the steel of the pliers’ jaws not flexing when the band clamp is fully open and the pliers’ locking mechanism locking the band clamp fully open. I have also found that are times that Channel-Loc pliers work event better than purpose-made band clamp pliers for removing and installing the band clamps.
The Process #
Step 1 – Drain Coolant #
The first step is to drain the coolant. Please wear safety glasses to keep coolant out of your eyes. I find it best to start by separating the engine’s coolant hoses from the underfloor metal pipe. This will empty a lot of the coolant from the system. However, there is still plenty left in the interior heater circuit and the engine. The hoses that connect the engine cooling system to the interior heater circuit are situated right above the rear subframe. They are also attached to the main coolant hoses using plastic connectors. I found it impossible to separate the heater hoses from the plastic hose connectors on our second F. As a result I resorted to cutting both hoses going to the interior heater circuit.
Step 2 – Getting Access #
Gaining access to the heater hoses is not easy. You must remove almost the entire interior. All except for the dash and the heater assembly. Out come the seats, bulkhead trim (aka t-bar), armrest, rear stowage bin. Also the centre console (don’t forget to disconnect the wires going to the cigar lighter), handbrake handle and gaiter. Continue with the gear knob, gear lever gaiter, fascia (a two-part assembly in early cars), heater controls, the bracket that holds the heater controls. Finally. the bracket that is directly in front of the heater valve.
Before removing the pipes and hoses, mark the alignment of the different hoses to the pipes to the heater valve and to the heater matrix. Use a wax pencil. This way you can reassemble the system without putting undo stresses on the hoses. This is to minimize the chance of a hose prematurely failing.
Step 3 – Heater Valve #
To remove the heater valve, remove the two screws used to attach the heater valve bracket to the heater assembly. Next, you will have to disconnect the cable that connects the dash’s heater control to the heater valve. Pay attention to how the clip holding the cable is attached and the location of the control cable with respect to the clip.
Once the heater valve and its hoses are removed from the dash, mark the alignment of the hoses to the valve.The two hoses connected to the valve are very similar, easy to mistake which is which.
I found the most difficult hoses to remove are the two hoses that connect to the heater matrix because of the proximity to the dash. It is likely that only the cable-clamp pliers can access the two band clamps on the hoses at heater matrix.
Step 4 – Heater to Engine Coolant Hoses #
To replace the two hoses that connect the heater to the engine coolant system, the heater pipes must be removed. These two pipes must have been one of the first items installed in the car during assembly because they do not easily come out or go back in. First, from under the car, spray some silicone lubricant on the two hoses that go through the firewall so that they will slide out of the body tunnel seal. Now pull the pipes forward and up towards the centre vents. The pipes will be able to just clear the centre vents…just. Be careful not to hit the pipes on the windscreen. Before you can fully remove the pipes from the car, you need to disconnect the two hoses at the other end of the pipes.
I wasn’t originally planning to replace the heater pipes but once I got the pipes out of the first car, I discovered that the pipe ends were in very bad condition, significant pipe wall thickness loss due to corrosion. NOS pipes, that were left over from the production of the SAIC TFs, are available from Rimmer Bros. Order these pipes at the same time you are ordering the hoses, rather than having to place a second order like I did.
When it comes to reinstalling the pipes, I found it easiest to install the two hoses that go out through the firewall after getting the pipes down past the dash. You will need a second person to help you fish the two hoses through the firewall’s rubber seal, remember to spray the hoses with a bit of silicon before going through the rubber seal. I found by using my fingers stuck through the two holes in the rubber seal into the end of the hoses provided enough of a guide to get the hoses through the rubber seal, while my wife pushed on the pipes. MY wife didn’t find pushing on the pipes to be an easy task, it took a lot of effort to shove the hoses and pipes into the correct spot.
Next reattach the two hoses to the other end of the pipe before affixing the pipe to the body of the car. Don’t forget to put the band clamps onto the pipe before pushing the hoses onto the pipe.
Step 5 – Heater Matrix #
Reattaching the two hoses to the heater matrix. As mentioned earlier, I marked the alignment of the hoses to the heater matrix with a wax pencil prior to disassembly. Using the old hoses, I put new marks on the new hoses and then aligned with the marks on the heater matrix. Make sure to install the band clamps on the new hoses before installing. Reinstalling the band clamps is difficult but doable using the cable-clamp pliers.
Conclusions #
I completed this project during the winter of 2022/23. Since then I have noticed five other people posting on the MGF-specific forums and Facebook groups, about coolant leaks. Typically in the centre console (leaking at the heater valve), or coolant behind the seats. The cause of these cases are all related to coming from the pipes and hoses connected near the firewall. Given that these hoses and pipes can be up to 27 years old, its not very surprising. Given my own personal findings concerning pipe corrosion, it is worth considering replacing these hoses and pipes on a pre-emptive basis. This is perhaps particularly true when you consider that they are all hidden from view.
Other Material #
I’ve built this website and spent time on the knowledge base to bring together a lot of information I have collected from around the internet. The intent is making it easy to find rather than having to know about and have skills with search engine query terms to get what you were looking for. Please make use of the knowledge base.
