The 75 and ZT Owners Club Forums - View Single Post

T-Cut · 2nd October 2019, 21:43

When PRTs were first introduced by MGR they were rated on two factors, the nominal opening temperature and the pressure relief spring rating (light/medium/hard). These various PRTs were identified by their colour. The 87-88C/medium spring version was buff coloured and was factory fitted to the 1.8Turbos. Mine ran at 90-100°C, with a distinct relief valve opening point at 2000rpm. The relevance of relief pressure rating can be found by reading early MGR articles about mitigating hgf in the 1.8 engine.

Several years after I bought the car new, as an experiment I swapped the buff PRT for a black version, which by that time was the one quoted by Rimmer for the 1.8T engine. Part numbers soon became meaningless, because the lower temperature black version had the same part number as the buff one running around 8 degrees hotter.

Technically, they are different stats and my 1.8T runs at 87-90C with the black one. I've never noticed any pump pressure relief with it and I suspect it is the 'hard' spring. However, if you read up about PRTs on the Seloc Techwiki site (about the only place anything of any sense was published about PRTs) they now recommend the grey version. Unfortunately, the grey one I bought from a Land Rover outlet was no different in spring tension from the black one I'm using, so I sent it back.

So, whatever MGR intended with PRTs has now been lost to the winds of time and the only variation anyone identifies is the opening temperature. From my readings about current era PRTs, you really don't know what running characteristics you'll get from them and suppliers are none the wiser either.

Seloc Techwiki The PRT: https://wiki.seloc.org/a/Pressure_Re...ote_Thermostat

TC

2nd October 2019, 21:43	#5
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	When PRTs were first introduced by MGR they were rated on two factors, the nominal opening temperature and the pressure relief spring rating (light/medium/hard). These various PRTs were identified by their colour. The 87-88C/medium spring version was buff coloured and was factory fitted to the 1.8Turbos. Mine ran at 90-100°C, with a distinct relief valve opening point at 2000rpm. The relevance of relief pressure rating can be found by reading early MGR articles about mitigating hgf in the 1.8 engine. Several years after I bought the car new, as an experiment I swapped the buff PRT for a black version, which by that time was the one quoted by Rimmer for the 1.8T engine. Part numbers soon became meaningless, because the lower temperature black version had the same part number as the buff one running around 8 degrees hotter. Technically, they are different stats and my 1.8T runs at 87-90C with the black one. I've never noticed any pump pressure relief with it and I suspect it is the 'hard' spring. However, if you read up about PRTs on the Seloc Techwiki site (about the only place anything of any sense was published about PRTs) they now recommend the grey version. Unfortunately, the grey one I bought from a Land Rover outlet was no different in spring tension from the black one I'm using, so I sent it back. So, whatever MGR intended with PRTs has now been lost to the winds of time and the only variation anyone identifies is the opening temperature. From my readings about current era PRTs, you really don't know what running characteristics you'll get from them and suppliers are none the wiser either. Seloc Techwiki The PRT: https://wiki.seloc.org/a/Pressure_Re...ote_Thermostat TC Last edited by T-Cut; 2nd October 2019 at 21:48..