Thermoguard ThermoGuard Instruments
founded in Alice Springs, NT, Australia - Australia's Red Centre
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Installation

Installation of the ThermoGuard EGT Gauge kit is quite straightforward but generally does require some skilled use of tools. Well-equipped 'home mechanics' should have no difficulty with the fitting but those without suitable experience or equipment might be better advised to seek the services of an experienced diesel or turbo-charger specialist.

The following sections describe in general terms the fitting of the thermocouple sensor and the indicator unit. However, each make and model of vehicle may present slightly different problems in choosing the optimum location and access for installation.

Thermocouple Sensor

The ThermoGuard EGT Gauge kit includes a heavy-duty industrial-quality Type K thermocouple to sense EGT. It is a mineral insulated, metal sheathed (MIMS) unit with a 6 mm diameter stainless-steel sheath, capable of many years of reliable service when installed correctly. The sensor is fixed into the engine's exhaust system using a stainless-steel compression fitting.

Where? (Before or after the turbo-charger?)

Upstream Installation

Detail of the Thermoguard thermocouple sensor and compression fitting screwed  
into the exhaust manifold of a Land Rover Defender Td5 turbo-diesel engine

In my opinion, by far the best location for installing an EGT sensor is in the exhaust manifold, upstream of the turbo-charger exhaust turbine inlet. As the exhaust gas expands through the exhaust turbine, the pressure and temperature of the gasses reduces markedly. However, it is the hotter upstream temperatures to which the vital turbo components are subjected. That is, the turbine housing, turbine blade tips and wastegate valve 'see' the hotter upstream gas, which can heat them to damaging temperatures.

A location which samples the exhaust gas from all cylinders (or all cylinders in one bank, in the case of a 'vee' engine) is desirable, rather than a location which effectively samples the exhaust from only one or two cylinders.

Downstream Installation

Detail of the Thermoguard thermocouple sensor and compression fitting screwed  
into a threaded boss welded into the turbo exhaust pipe on a Nissan TD42Ti turbo-diesel engine

Installing an EGT sensor downstream from a turbo-charger will result in temperature measurements which may be several hundred degrees C lower than those upstream of the exhaust turbine in certain circumstances. This temperature drop is largely unpredictable and may give the driver a false sense of security unless a lower temperature limit is adhered to.

However in some vehicles, access to the exhaust manifold is simply too difficult and/or the owner is not prepared to strip the engine to the extent necessary to install in the manifold. Some owners also find that their aftermarket free-flowing exhaust systems already have a sensor mounting point fitted to the turbo outlet pipe. In these cases, the owner may prefer to use a downstream sensor location and accept the compromises of this location.

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How? (What tools and materials are required?)

Detail of the Thermoguard compression fitting, showing the thermocouple clamped  
into position

Regardless of the location chosen, the thermocouple sensor is fixed to the engine with a stainless-steel compression fitting supplied with each kit.

The standard ThermoGuard EGT Gauge kit includes a stainless-steel compression fitting with a 1/8" BSPT Male thread. This thread is also known as an ISO 7.1 R1/8 thread. [The "1/8" refers to the 'nominal bore' of tubing typically used with this size fitting. The thread is actually almost 10mm in overall diameter and is more than strong enough for the task.]

Upstream installation

In almost all modern turbo-diesel engines*, it is necessary to drill a hole through the exhaust manifold and cut a thread into it to enable the compression fitting to be screwed in.

Any competent diesel or turbocharger specialist should be able to perform the drilling and tapping of the manifold. We are able to supply the correct size drill bits and thread taps, if required.

* The Land Rover 300Tdi non-EGR engine (Australian specification) is an exception.

Downstream installation

A number of aftermarket exhaust systems include a threaded boss welded into the exhaust pipe, just downstream of the turbo-charger. This is often a 1/4" BSPT female fitting. In this case, we can substitute a 1/4" BSPT male compression fitting in the ThermoGuard EGT Gauge kit, if requested, at no extra charge. Australian-made DTS and MTQ aftermarket turbo systems have an M18 x 1.5 metric threaded boss. For these systems, we can supply a suitable adapter for a small additional charge. Compression fittings with other sizes and types of thread (e.g. American NPT thread) are available if required.

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Digital Indicator

Detail of the Thermoguard digital indicator installed into the centre console  
of a Nissan GU Patrol Detail of the Thermoguard digital indicator installed into the centre console  
of a Nissan GQ Patrol

The ThermoGuard EGT Gauge digital indicator has a bright red LED display which is easily viewable in daylight and at night.

The indicator unit is intended for mounting into a flat panel. The indicator front panel is 77(w) x 35(h) mm. It requires a rectangular cut-out of 71 x 29mm. The unit is 77mm deep but, as the wiring is rear-connected, about 90mm depth is required behind the front panel. Th e unit includes removable ratchet clips to ensure a snug fit to the panel.

For a dimensioned image of the indicator unit, please click here.


If an in-dash installation is not possible or not desired, the indicator may be supplied in an optional rugged ABS plastic Instrument Case. This can be attached on or under the dash and makes it particularly easy to transfer the indicator between vehicles. The Instrument Case is 130(w) x 35(h) x 90(d) mm.


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Detail of the Thermoguard digital indicator within the optional Instrument  
Case Detail of the Thermoguard digital indicator and instrument case installed on  
a vehicle dashboard
Copyright © 2004-2013 Ian Petersen