XPAG Overheating – a cure (or was it a pickle?)

At Stoneleigh in February I met a young TC owner (a rare find!) – almost certainly the youngest I had ever conversed with.

Stuart Maddock had ‘served his apprenticeship’ on ‘proper’ MGs under the guidance of his late grandfather in the latter day 90s/early 00s. Initially helping with tasks such as engine cleaning and minor bodywork adjustments on a PA, he progressed to assisting with the rebuild of a TC.

By the summer of 2005 the TC was ready for use and Stuart started taking it for short runs in order to familiarise himself with the driving technique required of a classic. In doing so he collected a long list of faults, which he rectified one by one.

Becoming more adventurous, he tried some longer trips and discovered the dreaded overheating lurgy. It manifested itself by stalling and leaving him stranded for upwards of an hour.

In an effort to avoid this annoying (and embarrassing) tendency, Stuart started to plan trips on the basis of one hour’s drive away, or to leave either early or late in the day when the ambient temperature was a lot cooler. He became something of a regular spectator at cricket matches in Datchet, Windsor and Eaton whilst waiting for the car to cool down.

Taking in the pleasant sound of leather on willow in a plush green open space was quite tolerable but overheating at traffic lights on a dual carriageway at a four way interchange on the Reading IDR was certainly not!

Fortunately, being a Structural Engineer by profession, Stuart was carrying a full hazard kit and luminous yellow jacket in the car, so was able to warn the traffic of the breakdown.

A diesel engined police car, which arrived on the scene to investigate what all the fuss was about, unfortunately caught the overheating bug as a result of keeping the TC company with its engine idling for 30 minutes. Whereupon, Stuart pulled away to get off the road and cool down in a quieter place, waving away an RAC patrol van in the process.

Enough was enough – something had to be done! After mulling over the problem for quite some time Stuart eventually concurred with his father that the replacement of the thermostat was needed. A phone call to NTG resulted in a nice new shiny thermostat arriving through the letterbox. Three hours of work replacing the part and cleaning everything up resulted in……….yes, you’ve guessed it!! …….no improvement whatsoever!

This had now become a serious matter and further investigation was a priority. After pulling off all the remaining pipework for the cooling system and looking at the engine internals from the removal of the thermostat and connections, everything looked totally silted up with 5-7mm of deposited residue on all surfaces. Even the replaced thermostat became silted up within weeks of installation.

Photo 1 showing the ‘orrible crud on the new thermostat which had only recently been fitted.


Stuart takes over the story from now on:

“I attempted a few suggestions from forums, including removal of the thermostat and even drilling holes to assist a constant flow of water. Still there was no improvement.

Being as the problem could hardly get much worse I asked a friend to knock up a new mounting piece to bolt on to the engine and during a couple of night school classes I perfected the part I had in mind that would allow for the engine to be cleaned in situ.

A trip to Beaulieu Autojumble later (a three months’ wait) and I had all the pipework I needed to run through a cleaning mixture of heating system descaler, light acid and the nastiest cleaning mixtures the general public can buy.

Using hot water in a plastic tub and an electric pump, the mixture was pumped into the top of the engine block and run back out with pipework over the front apron and into the tub. A heating element was added to the tub to keep the mixture hot and 24 hours later of using a very strong to weak mixture I then repeated using a neutralising agent. The old thermostat was placed in the tub and came out like new.

The water that came off looked like a smurf that had been in the jungle for three months. The TC had been sat for over 20 years prior to its first use.

Rebuilding the cooling system and taking the car out was a revelation. The TC now had acceleration; the engine lasted all day without overheating and was happy in heavy traffic.

I then turned my attention to the radiator and decided that in principle, the same system could be used to clean it. I’d already asked if this could be done and was told ‘no’ by almost everybody. I was advised to take the radiator out or buy a new one (at vast expense!).

Another trip to Beaulieu with yet more puzzled looks from a very bemused seller as to why I was trying to piece together what can only be described as an imitation elephant’s trunk from a combination of Vauxhall Victor, MGB GT and Austin hose pipes. Still, I had my system working on the radiator in no time and for good measure I re- cleaned the engine block.

Photo 2 – cleaning the radiator in situ.


Attention has also been given to the problem of fuel vaporisation with liberal use of exhaust wrap.

JXK 47 has been running now for the last five years without a single engine problem. My system works on any radiator of the T-Series and on all XPAG engines. I have also used the system on two other vehicles and both owners have reported back that there has been no recurrence of overheating problems.

My TC seems to be getting better each year and I put this down to careful maintenance.

Stuart Maddock

JXK 47 (TC8120) – very cool!


Ed’s Note: Stuart is hoping that someone out there can help with the history of his car. It is known that it was originally an export model and was used for hill climbing and street racing. Apart from this the car sat in pieces for around 20 years.

5 thoughts on “XPAG Overheating – a cure (or was it a pickle?)

  1. Doug McWilliam says:

    I wonder about the local water supply? It looks to be high in Calcium Bicarbonate which on heating deposits out Calcium Carbonate.
    What cleaning agent was used?
    If it was acid, then the cleaning solution would have “fizzed” quite dramatically as the CaCO3 dissolved and liberated CO2

  2. Jeffrey Delk says:

    Could you provide specific details on the actual mixture of your cleaning solutions? This is an interesting and creative solution to an often overlooked aspect of the overheating xpag.
    Thanks in advance

  3. JOHN JAMES says:

    Stuart Maddock has replied as follows:

    “I’m away on holiday atm, just a half hour to reply.

    from memory and this is pushing it. The water jacket was flushed with good old Thames water in the 90s using a hose pipe.

    Fairly sure it had a mixture of water, anti freeze and lots of other stuff in there.

    When I ran the solution through it, it was fixing, giving off some vile smells and foamed up at least 5 inches in the ponding tub from the mixture I pumped through.

    Sadly, I know less about water, mixtures and correct fluid in there. It’s now running, off tap water and inhibitor and runing perfectly”.

  4. Gordon Higginbotham says:

    Fascinating article. Please could you let us know the details of the cleaning solution and the neutralising solutions used. Many thanks.

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