K-Series engine temp rising

[Beagler]

The expansion tank cap has a pressure of 115 kpa (16lb/sq in) is the cap functioning correctly. No pressure = lower boiling point of coolant.

[samsul]

Hi,

Brand new cap on the expansion tank so can hopefully rule that out.

Bit of a breakthrough...if I hold a steady throttle input when the temp rises at idle I can bring temps down to normal operating range within 20 seconds. That implies the coolant isn't circulating fast enough on its own so I think I am narrowing the issue down to thermostat or water pump. 

Thanks for all advice. It's getting there!

[Jonathan Kay]

"Bit of a breakthrough...if I hold a steady throttle input when the temp rises at idle I can bring temps down to normal operating range within 20 seconds. That implies the coolant isn't circulating fast enough on its own so I think I am narrowing the issue down to thermostat or water pump."

That is interesting. I was trying to think of everything that's different between driving and idling.

Jonathan

[john milner]

I may be reading this thread incorrectly but at the start the temperatures were from the dash gauge which is now suspected as giving faulty readings so now OBD readings are being used. Could this be like comparing apples & pears?

When up to temperature my dash reads in the low 80s, rises when stationary and quickly drops when the fan starts or I get moving. I think this is normal but I do not know what normal OBD readings are. I do not have a hole in the thermostat or an additional high point bleed valve.

Any leaks can cause erratic readings as loss of pressure will cause a temperature rise. Heat expansion could temporarily close a small gap, pressure open a gap etc. 

The easiest thing right now is to get the dash gauge working so you have some well known figures to compare with. Most likely this is due to a faulty sensor which is easily swapped out with minimal coolant loss.

Temperature gauge tests https://www.tom-seven.stillgame.ch/Main/CTS_Meter_logic.htm

If the temperatures are still not correct then the most likely causes are trapped air or faulty thermostat. If satisfied it is not trapped air then the thermostat is a relatively cheap thing to swap and a small hole may help with operation and the shifting of bubbles.

If the coolant pump is failing I would have thought there would be some funny noises going on due to bearing failure. Some pumps have plastic blades so an unlikely possibility is some have broken off.

Blocked waterways are at the bottom of my guess list.

[david nelson]

I think I may have read this wrong

on start up you get 80 degrees  but after 20 mins if you get stuck in traffic the temp goes up into the 90+ mark

This all sounds normal.

WT on the ECU may not be the same as on the Gauge ( When hot mine are different by 10 degrees.) ECU higher than gauge.

you turn the engine off when it gets in the 90 + temp but the fan will not start till 92 degrees is reached.

My K in traffic would always go up so fitted over ride switch. 

To me all sounds normal. 

getting the remote pipe as in an earlier post may give you confidence all is well as it can be put out of the way of the exhaust. 

 

 

[John Vine]

Re #29:

...loss of pressure will cause a temperature rise.

I don't follow that. Could you possibly elaborate?

JV

 

 

[john milner]

Re #31

I am wrong while simultaneously being correct.

I was trying to say in as few words as possible that a leak will cause a pressure drop which will cause a risk of boiling off. So my saying "...loss of pressure will cause a temperature rise." is an incomplete statement.

Coolant shifts heat away from hot spots. Boiling off will result less or no coolant. If that does happen an increase in hot spot temperatures will follow.

I may also be wrong as getting particularly pedantic, no coolant could result in lower recorded temperatures as the sensors will not be in contact with any coolant even if the engine is completely buggered due to warping, melting and fire.

 

[samsul]

Thanks all.

I have been taking readings from the gauge and OB readouts and looking for trends within rather than between. So I am happy that I have 2 consistent baselines to work from.

I have now replaced the thermostat with a brand new, and tested, 88 degree stat with a 3mm hole drilled in the top.

I have installed a bleed valve at the heater matrix end of the system, as high as I can get it.

I have replaced the expansion tank cap.

I have flushed the coolant and replaced with new.

I have refilled and done my best to re-bleed the system with the front of the car in the air.

Still, the car runs about 10 degrees hotter than it used to - around 88-92C now compared to 80C previously. The temp will increase from this point when stationary or with no throttle input. However, on most occasions, if I hold a steady throttle at idle the temps will drop by 10 degrees rapidly. This is still puzzling me as I suspected a sticky thermostat, which has now been ruled out. This, I think leaves the pump, a blockage, or I still have a flipping air lock! 

 

[revilla]

What kind of radiator have you got Sam? I've seen this with a triple pass race type radiator, the water pump just couldn't push the water through it fast enough at idle.

[samsul]

Hi Andrew,

I am not sure what radiator is on the car so have taken a couple of pics:

Best,

Sam

 

[Jonathan Kay]

[revilla]

No that looks like a regular radiator.

Have you relocated the temperature senders to a submarine pipe yet as others have suggested? Although heat-soak from the exhaust sounds less likely if a bit of throttle brings the temperature back down again.

[tangomikeromeo]

That all looks familiar. Tip from @Oilyhands is to elevate the front.  Chock the rears. Set the jack on boards and lift. And lift. More. Is the jack at max height? That'll probably do. Is it high-lift? Even better  

Start and on tick over, there will be a series of burps and farts for 5 minutes until you are 'purged'. 

[Jonathan Kay]

The effect of engine speed that samsul and revilla describe doesn't sound to me like what happens when air is left in the system on a K series.

Jonathan

[revilla]

If you're really convinced you have a problem, it may be worth inspecting the water pump. It's not a trivial job though, you obviously have to drain the coolant and you need to partially remove and refit the cam belt. With care (and wads of tissue stuffed between the cam belt pulleys and the cover to stop the belt slipping on the pulleys) you can probably just do it by releasing the belt tension, but make sure you do it in safe position with a cam lock installed and don't just trust that it hasn't slipped a tooth at the crank pulley afterwards, check. Some K water pumps had inferior metal impellers or worse still plastic impellers that were prone to braking up. If your water pump is struggling to keep the water circulating at idle it won't be good for the head.

[Fridybrydy]

Evening, Replacing the antifreeze every couple of years or so and after a water pump and cambelt replacement I've always had issues with fluctuating temperatures on my 1.8 k series.  I honestly do believe it is still down to air in the system as perseverance seems to win ever time. You'll find lots of treads going back years on this issue, a great many regarding the best way to bleed the system. To this end I have fitted a bleed valve at the highest point in front of the small heater matrix and I think this helps but doesn't cure.

I had ear marked replacing a number of heater hoses due to age, just afore the Taffia fish and chip run. However foolishly, after adding an email request for stock items from Caterham, (Three weeks was quoted, but nothing received), I did the f & c run (traveling from Yorkshire) without replacing the degraded hoses only to have the lower radiator hose give way on my return journey 100 miles from home. The AA (Actual local partner) came to the rescue with a replacement hose close enough to fit. He then spent the next 2 hours trying to bleed the system even doing a snift test to see if my head gasket had failed. Eventually, re-filling the system several times, top up from my bleed valve, massaging the hose at all points, opening and closing the heater matrix valve, running the engine with the expansion tank cap off and allowing it to overflow. After some awful sounding noises, air moving around the system, and it may be a bit by chance, he did get the system bleed. All hoses hot, all area's of the radiator hot (a good one to watch for). The car never missed a beat for most of the journey home with a steady temperature just over 80 degrees. About 5 miles from home I opened the heater matrix valve and the temperature dropped by about 40 degrees. Closed the heater matrix valve and the temperature rose to just above 100 degrees.  Ahhhhh!!!. Any how, this is why I believe it is air in the system. I am shortly to take delivery of cooling hoses from KitCarDirect and therefore once more into the breach.

I am however going to follow a tip from SM25T, and follow the instructions as detailed in Modifying the K Series coolant circuit by Ian Blakeman from LowFlying archive Sep-12. Along with replacing the thermostat (as I'm in there) and drilling a small hole in the replacement before fitment. I'll let you know how I get on. Will be post Platinum Jubilee Celebrations. God Save The Queen

Perseverance

Fridybrydy

[SM25T]

Hi there. Good to see you posting. Missed you on F&C run. Do you need a photo of hole location in thermostat baseplate ? Ian

Edit ... Found it !

 

 

 

[SLR No.77]

With a hole drilled in the stat as shown by Ian (#42) and a bleed-T fitted at the high point, bypass hose or in front of the heater, there's no need to raise the front of the car or actually "bleed" the system as such.  Simply remove the expansion cap and radiator bleed screw, then fill the system slowly via the bleed-T.  When coolant escapes from the radiator refit the bung, when it reaches the correct level in the expansion tank refit the cap, then continue filling until it is overflowing from the bleed-T.  Easy peasy and works every time. The key is to fill very slowly.

Stu.

[revilla]

Wot Stu said.

Plus make sure the heater (if fitted) is turned fully on, to let air out and water in.

[SM25T]

Note the hole must be at the top when fitted into the housing ... as per the photo.

[Fridybrydy]

Thanks lads, for all your tips and Ian for the photo. A picture paints a 1000 words.

Cooling hoses arriving today.

[Fridybrydy]

Any suggestions where I can pick up a new 1.8 k series 82 degree thermostat please?

[Jonathan Kay]

I'd start with Redline.

Jonathan

[SM25T]

Or local Halfords.

Part number 

Rover OEM Type:GTS282

Quinton Hazell:QTH115K

[samsul]

Hi, thanks for replies.

The bleed tee and extremely slow filling seems to have done the trick. The car is now running significantly cooler - around 70C - and the temp stabilises at idle, even after a decent run. 

I am a bit concerned by the low coolant temp but better than hot! 

I have attached a pic of the location of the bleed tee; not perfect as I didn't have the space to install above the heater valve but apparently effective anyway. 

One thing to note is that holding a steady throttle at idle no longer affects the temp. Therefore, perhaps I had a small airlock/air bubble all along and by applying throttle, and circulating more coolant more quickly, I was able to negate the effects?

I am going to do some more rigorous testing ahead of Le Mans Classic in a few weeks, where I am sure we'll get stuck in some serious traffic. 

*Apologies for the strange angle of the photo - not sure why the forum has rotated the image?