High Water Temps after switching off

[nikp]

I\'ve made some observations about water temps since fitting my Apexi ECU.

After switching off the engine the high temps of the engine and it\'s ancillaries can bring the temperature of the coolant up to very high temperatures (I\'ve seen 111degrees!!!). Now, firstly, these temps are different to those seen at the after market coolant temp gauge i have mounted just before the rad inlet. Can be a difference of up to 10 degrees. So, my first question is are these temperatures going to any damage to the engine when it is off?

Therefore, if they can damage the engine, i thought about the idea of having an electric water pump and timer fitted to turn the fans on when the engine is off and run the water round the whole system to help cool things down. Has anyone down this? If so, how? If not, what are peoples thoughts on this idea? Worthwhile? Waste of time?

Any other thoughts?

[davegttph1]

your gonna see the difference because I presume the Apexi is measuring the coolant in the block rather than that in the radiator...

I would have thought you\'d be fine although I tend to sit with the engine running and the A/C switched on and wait for the temp to drop to 84oC before I switch it off. obviously it\'ll rise close to 100 but shouldnt cause any problems but switching it off at 100oC wouldnt be wise IMO....

[nikp]

Yeah, i was aware why I\'m getting the high temps, etc - just wondering whether it\'s worth doing anything about it.

I\'m too impatient to sit there waiting for the temps to come down with the air con on!

[davegttph1]

Ahh but thats why I try and cool it before I pull up. Always have the A/c on when I hit 90oC

[nikp]

Getting into the realms of what temperature is dangerous on an FD again here! :p

I\'m of the opinion that 90 is not a bad temp to have. Only when it starts creeping towards 100 is when i start getting concerned. Therefore, speaking of which, why did mazda recall the 1.3 bar radiator cap (Which would allow a higher boiling point of water) with a 0.9 bar cap (Which would mean a lower boiling point of water - below 100 degrees if my physics is not too rusty!) Anyone any ideas?

[John Yorke]

The recall as I understand was because on the earlier models the additional pressure caused water seal failure :xconfused

I would not be concerned seeing 110 after a run, what you should be worrying about is your temps when driving, your thermostat operates at 90\' so you should not see DRIVING temps above 95 -98 unless you are ragging it, doing track work, \'private race track\' :rolleyes:  driving anything over 105c and I would be slowing down and doing all I could to get the temps back below 100c.
HTH

[nikp]

I see - poor design in water seals by the sounds of it then - if they can\'t hold 1.3 bar of pressure!

Surely its also possible to see temps of over 95 if you are crawling a lot in traffic? In other words not getting much fast flowing cool air through the radiator.

[John Yorke]

I see - poor design in water seals by the sounds of it then - if they can\'t hold 1.3 bar of pressure!

Surely its also possible to see temps of over 95 if you are crawling a lot in traffic? In other words not getting much fast flowing cool air through the radiator.

Thats why mazda fitted 2 fans :wiggle  and they did improve the seals, if you cannot maintain 95 or below I would suggest you have some form of blockage either your stat is not working or yer rad is starting to silt up, remember your car is 10 or so years old and things do get clogged up.

[nikp]

Ok, my FD is blocked up somewhere then! :p I have seen some high ish temps, and i was beginning to suspect that i was blocked. Have changed the thermostat already, so i know that\'s pucker. When i changed it i didn\'t flush (Ooh er!), so probably will do at the weekend.

[Mave]

Getting into the realms of what temperature is dangerous on an FD again here! :p

I\'m of the opinion that 90 is not a bad temp to have. Only when it starts creeping towards 100 is when i start getting concerned. Therefore, speaking of which, why did mazda recall the 1.3 bar radiator cap (Which would allow a higher boiling point of water) with a 0.9 bar cap (Which would mean a lower boiling point of water - below 100 degrees if my physics is not too rusty!) Anyone any ideas?

I suspect your physics isn\'t rusty, but your interpretation of the pressure is.... 0.9bar is 0.9bar gauge, ie 0.9bar above atmospheric pressure. Therefore the boiling temperature of the water will be above 100C, and then higher again depending on what coolant you use. Incidentally, IMHO it\'s not the bulk water temeprature that\'s the problem, it\'s the local temperatures near hotspots Incidentally, what kind of number plate do you have? I was worrying about my water temps, and changed my square plate to a rectangular one, I got about 10C drop around town. Next step is a stick on one to get even more air in.....

[Trevrx]

I thought mazda changed the cap to 0.9bar because the AST\'s were blowing under 1.3 bar?

My Apexi used to read about 110 degrees after switching off/heat soak too.

BTW, the FD thermostat opens at 83 degrees, you should know exactly what temp yours opens at as you have a temp guage before the rad which blings into life at what temp?

[nikp]

I suspect your physics isn\'t rusty, but your interpretation of the pressure is.... 0.9bar is 0.9bar gauge, ie 0.9bar above atmospheric pressure.

Oh yeah - that\'s a good point! Can anyone confirm whether the pressure of the cap is 0.9bar or actually 1.9bar?

Incidentally, my coolant temperatures seemed to be perfectly fine today! Some of the worst traffic i have seen in Bristol this morning, I didn\'t see temps over 95 at all. Wierd... Maybe I just panic about my rex too much!! :p

BTW, the FD thermostat opens at 83 degrees, you should know exactly what temp yours opens at as you have a temp guage before the rad which blings into life at what temp?

This is true - but when it opens first time after starting the car, the coolant after the point of the thermostat is cold, therefore the temp gauge shows something like 70 degrees as the hot water is mixing with much cooler water.

[Mave]

Oh yeah - that\'s a good point! Can anyone confirm whether the pressure of the cap is 0.9bar or actually 1.9bar?.

It\'s 0.9 bar gauge, which is the same as 1.9 bar absolute. I\'m 100% sure it isn\'t 0.9 bar absolute....

Incidentally, my coolant temperatures seemed to be perfectly fine today! Some of the worst traffic i have seen in Bristol this morning, I didn\'t see temps over 95 at all. Wierd... Maybe I just panic about my rex too much!! :p

What\'s going on? It took me ages to get into work this morning (through Southmead), I was in my Alfa, it was the first time I had the radiator fan going since the summer

[nikp]

Cool - 1.9 bar it is! That means boiling point is above 100 degrees c - but not quite sure how much higher!

Yeah, traffic was a right pain. However, coming back at lunchtime it was really clear! Did everyone just decided to hop into their cars this morning between 8 and 9!?

[davegttph1]

Remember though you shouldnt be using water if your using proper coolant then your figures probably change alot more as it\'ll have a higher boiling point that water  

oh and btw, I had trouble getting into work this morning too.... although I was in the Cougar