chriscoates81
New member
Preferably more upnorth too its a 3 hour drive to coventry for me!
Low Temperature Thermostat
- Thread starter Rodney Naghar
- Start date
Porsche now recommend using the vacuum fill method but this was the recommended method when the 996 was launched: 1) Lift spring on bleeder at the top of coolant tank 2)Run engine at idle speed and add coolant until no more coolant flows into the cooling system when the engine is revved at moderate speeds. Coolant level is now at lower edge of filler neck. Coolant temp must not exceed 80 degrees. 3)Close coolant tank and warm engine to operating temperature at 2500 rpm until thermostat opens approx 10 minutes later. The radiator supply and return lines in the front wheel arch housing must be hot. 4)Forcibly engage both secondary fans by using a relay jumper at relay 20 and 22. 5)Allow engine to run an additional 5 minutes at 2500 rpm. Every 30 seconds briefly rev engine to 5000 rpm as the surges is important to purge the air. The coolant light may light during the bleeding process. Reset by restarting engine. Interrupt procedure if coolant level falls below min mark. Open coolant tank carefully to depressurise it then fill with coolant and intermittently rev engine again. 6) Deactivate the auxillary fans by replacing the relay jumpers with the relays. 7)Wait until coolant has cooled to 80 degrees (approx 25minutes) 8)Open the coolant tank carefully again and fill with coolant to the lower edge of the filler neck which corresponds to the max level when cool. 9)Reposition bow on bleeder valve and collant tank cap.
thirteeneast
New member
996 = IMS Problem.
thirteeneast
New member
the upgrade stat opens 20 degree's lower/before the standard oem. Id like to do this too when I have a bit more spare cash.
Wow 20c? With a 997 it may be a good idea, but on a 996 I think you're trying to gild the lily while at the same time potentially losing significant power as the engine is running so much cooler than optimal. Did Baz mention anything about this?
I am not at work as I answer this (so don't have figures for power increases - but it is significant) ast the best temperature to run an engine for power is not the temperature that these cars run at. They run hotter than that to reduce emissions but produce more power when run cooler with the lower temperature thermostat and more at the temperature racing engines run at - so that criticism is inaccurate - sorry! I keep explaining - that the temperature of the cylinder heads and cylinders are running different to the last decades of engines designed the original way. Basically they are splitting the coolant path to run the heads cooler and the cylinders hotter than before. Hotter cylinders can reduce cylinder sealing and increase cylinder to piston wear (hence problems with scoring) and although the engines can be altered when apart to change that coolant flow balance - the only way to lower the cylinder temperature without is to fit a lower temperature thermostat. The temperatures you can read either on the dashboard or the air con unit are the result of mixing back together again - the coolant coming out of the heads with the coolant coming out of the cylinders and does not reveal the true cylinder temperatures. We have tested this with temperature sensors fitted into different parts of different engines before and after re-machining and with and without the lower temperature thermostat - so we do know exactly what we are talking about! Unfortunately on the bank 2 side of the engine (cylinder 4, 5 and 6) the cylinder coolant is hotter on the thrust side (the side the piston is pushing on the cylinder bore to produce power) but not on the bank 1 side - so the most vulnerable side is bank 2 (where 95% of failures also occur for that very reason). Part of the problem is bubbling in which localised boiling occurs at the cylinder outer surface and the result is magnified as gas bubbles don't convect temperature as well as a well vented coolant and cause a rapid localised rise in temperatures - which build more bubbles and so on - all in a few seconds of running. Therefore - although we cannot always predict which cylinder has failed - it is usually on that side. Once one has scored thereis usually an increase in oil consumption but the extra oil leaking up the cylinder combined with a lower compression pressure resulting tend to move the problem on to another cylinder that may then follow on failing later - and so on and so on until we have seen cylinders with all 6 bores damaged. Lots of other factors lead to unpredictability of the exact outcome - worn water pump impellors (plastic and as the bearing wears - often touch the rear of the housing in use), leaking radiators or expansion tank caps or seals - etc can all lead to lower coolant pressure which increases the risk of bubbling as liquids boil (or bubble up) at lower temperatures as the pressure reduces. Any bubbling not only upsets the cooling of the cylinder that does it first - but alters the flow of the other cylinders on that bank and also the other bank as well - so the permutations of how it all changes the flow rates and therefore individual temperatures is too random to be specific about. Blocked radiators (and air con condensers) also alter the temperatures and balances - it's a complex system although most regard it is simplicity itself. Although it would always be best to alter the flow inside the engine - at least lowering the normal running temperature is a step inthe right preventative direction - is inexpensive and a simple way to actually run with more power available - not less. Baz
Baz, I have emailed Hartech for price inc. delivery for the stat but received no response.
I see, thank you Baz. It would be interesting to see what power increases are available when you get back to work. Surely if you think there is no downside to this (apart from higher emissions/fuel consumption) this could be touted as an extremely cheap power upgrade and better for the engine overall - and therefore sell by the bucket load?
Baz - have you tried measuring temperatures with the clip on the coolant tank valve in the raised position? I believe this it a thermostat bypass valve, used when bleeding the system. When I had a coolant change on my C2 I ran it with the valve open for a couple of days to help bleed the system, and noted that it took a little longer to warm up, and that it ran a few degrees cooler. Cup cars run with the clip up all the time, by the way.
No it is more like 20 degrees Fahrenheight but of course varies with the car condition, ambients etc - it is just that opening the thermostat earlier always helps. Sorry if we are a bit slow to respond at the moment, our engine rebuild inquiries have become so frequent we are hardly ever off the phone dealing with them and the consequential increases in workload – orders – manufacturing – progressing – testing etc. This is not just from the UK now – presently 9 ovverseas orders – the furthest being an engine coming from Korea.. Despite expanding staff and facilities – and investment - we are never going to be able to satisfy demand and so – we are forced to prioritise inquiries until we get up to speed coping with the increased order rates. Please be patient - we are trying our best. Baz
After reading various articles i changed mine, its a reasonable diy job if you have a jack etc.
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