coolant/radiator numptie question

tuscan_thunder · Post by **tuscan_thunder** » Tue Mar 06, 2007 10:15 am

When the Elise is started, does coolant automatically flow from the radiator to the block?

Maybe I'm being thick, maybe this is an issue which has already been resolved, but is there, or should there be, a thermostat which holds the water in the block until it reaches a given temperature before it starts flowing to the rad? (which would surely help prevent any HGF issues?)

Maybe this is a problem which has been discussed several hundred times before though so apologies if it has.

cheers
J

MacK · Post by **MacK** » Tue Mar 06, 2007 10:49 am

There is a thermostat that stops the flow of coolant mixture to the radiator till the thermostat temp is reached.

I believe there are issues with the location of the 'stat, and many people would recommend fitting a 'remote 'stat' or a 'pressure relief stat'.

Do a search on Selcock about it

Rich H · Post by **Rich H** » Tue Mar 06, 2007 6:57 pm

What he said. The PRRT (Pressure relief remote thermostat) essentially creates a small loop of coolant external to the block and reduces thermal shock on the block, one of the alleged HGF causes.

Fitted to quite a few Loti as the rover setup was designed for a metro driving to the shops and back.

More to the point, why are you worried about the coolant system?!?!

robin · Post by **robin** » Tue Mar 06, 2007 8:39 pm

The standard arrangement has two bypass loops - a short one right there in the engine bay and a long one through the heater matrix to try and get early heat into the cabin.

The stat is on the return side, but when closed there is no real flow through rad, as the water has nowhere to go (stat closed downstream).

When the block and bypass loops reach the magic 80-90C the stat starts to open and lets water in from the freezing rad.

The block temp drops quite rapidly but worse there is a fair gradient from the cold inlet to the hot outlet. Once the water in the bypass has cooled to below 80-90 the stat closes.

So the temperature in the engine oscillates around the stat opening point and there is quite a gradient from inlet to outlet.

Meanwhile if you're pootling along the stat might be wide open because there isn't much flow and you need most of it to balance engine heat.

Then you floor it, water flow rate rises much faster than stat can react and so the engine temp dips then recovers.

To better balance temps and reduce the thermal gradient, the PRT was invented.

See Carlos site (just search for carlos and PRT and you should find it) for the details ...

Robin

MacK · Post by **MacK** » Wed Mar 07, 2007 9:07 am

RICHARDHUMBLE wrote: The PRRT (Pressure relief remote thermostat) essentially creates a small loop of coolant external to the block and reduces thermal shock on the block, one of the alleged HGF causes.

You may be aware, there is a recent thread on the 'cock about HGF and PRT and RT. And according to KingK there is no such thing as a PRRT, there is either a Pressure Relief Thermostat or a Remote Thermostat.

Good reading

Rich H · Post by **Rich H** » Wed Mar 07, 2007 9:13 am

Grey or cream coloured thermostat like thing off a Landrover, but GOCCTLTOAL doen't have the same ring to it...

Rich H · Post by **Rich H** » Wed Mar 07, 2007 9:14 am

Grey or cream coloured thermostat like thing off a Landrover, but GOCCTLTOAL doen't have the same ring to it...

MacK · Post by **MacK** » Wed Mar 07, 2007 9:16 am

A but which one, the grey or green open at different temps, don't they....