September 7, 2018 at 8:15 pm #4968
My 401 runs at at a temperature of 90 – 95 deg most of the time. I think that’s too high with not much margin of error left. It runs at this temp even at motorway speeds, not just in traffic.
I’ve checked the gauge, water pump, radiator (professionally flushed through), timing etc, had the head gasket changed and new valves and followers changed whilst we were at it, checked all the waterways, had the block crack-tested – all OK.
The radiator looks rather dense in terms of the number of fins and therefore perhaps insufficient airflow through.
Any views anyone? What should the general running temp be? What should the rad core spec be?September 7, 2018 at 11:01 pm #4969
I would say you are running about 10 deg too high if your gauge is giving you an accurate reading, you mention however that it does not go higher on the Motorway so that is a good sign I am running a 401 with a re cored rad and it is showing about 85 to 90 deg. The engine has done about a 100 miles post factory rebuild but this was done many years ago.
I had the rad rebuilt be a firm in Bridgend and it looks the same as the standard set up, I had another one done at the same time by a firm in Carmarthen who fitted a less dense modern core which they said offered better cooling but it is not as thick which to me means less capacity so if we do use on the next project I shall be watching the temperature carefully.
Some owners have fitted alloy rads and have given good reports of them in terms of lower running temps but I have no personal experience of those but someone who has may hopefully comment.
An electric fan may help either to replace or supplement the original, remember also if you have recently rebuilt the engine, tolerances being tighter may make it run hotter. Finally make sure the steam valve on the rad is working properly.September 7, 2018 at 11:12 pm #4970
Did you check the waterways in the block? These fill up with corrosion and calcium and must restrict cooling. One way to tell is to see if water flows freely out of the block drain tap. Alas, I think the only way to clear them is when the engine is taken out and stripped and acid cleaned. But calibrate your temperature gauge against another one to make sure it is not simply reading high, they are simple mechanical gadgets. Good luck!
StefanSeptember 10, 2018 at 4:24 pm #4971
Geoff and Stefan,
Thanks for your comments.
The temperature does go higher on the motorway, quite alarmingly so. I have to pull over and wait for it to cool down. It doesn’t lose any water though.
The gauge is spot on.
The waterways in the block have been cleared out.
I have removed the thermostat for better circulation.
Further thoughts?October 8, 2018 at 5:06 pm #5021
Water pump? is it actually circulating the water properly, also has the head been repaired as I have been told about one some years ago where a repair had blocked a waterway, a simple flow test should rule that out, Check the rad again by a different method when its up to operating temp stop the engine and run your hand over the Matrix if the temp is uniform it should be ok if however there are any cool or significantly cooler areas this would indicate a partial blockage which could be the cause of the problem other than that I think you have tried all the things I would look at.
Geoff.October 10, 2018 at 9:35 am #5028
Had a chat yesterday with my mechanic pal and he suggested the water pump impeller as an issue bearing in mind all the other checks you have done. I have never tried it myself but the manufacturers of Evans waterless coolant claim it reduces running temperatures, perhaps someone who has used it could confirm if this is the case.
Geoff.October 10, 2018 at 2:38 pm #5038
Thanks for this. I have fitted a replacement water pump and no change, so I think that rules out that suspect! My current theory is that, as it was ok before the head gasket was changed, something must have been disturbed or blocked in the block during that work.
The rad flows fine and temp over its surface is roughly uniform – checked with an ir temp gauge.
The block now runs much hotter than the head.
We know the gasket is ok and not blocking anything as the head has been taken off and checked again – it’sfine.
Maybe the block was getting a bit blocked up and something that has been done during the gasket change has blocked or loosened something else causing the temp to rise.
Maybe it needs a block flush through.
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