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K-Series engine temp rising


samsul

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Hi,

I have a 1.8 k-series SuperSport. Recently got the car out of storage and the engine temps are misbehaving.

For the first 30 mins of driving everything is as it should be; the coolant temp hovers around 80 Celsius in all conditions. However, thereafter the temp will do two things. Yesterday, the temp rose to around 95-98 Celsius whilst waiting at a light. Today, the temp remained at 85 but rose to around 95 just after I pulled away from a light. Conflicting behaviour. The only difference is that I bled the system in between. 

I jacked the nose up, got the engine running, released the clamp on the return from the heater matrix until coolant trickeld out, then I released the bleed screw on the top of the radiator in 3 second bursts to let any residual gas escape. 

I have also tightened all clamps on the coolant system. There is enough coolant and it's in good condition. I can't find any air leaks. The fan kicks in and is also in good condition. 

I have been running around with an OBDII reader plugged in so can confirm that the ECU coolant temp sensor and the gauge are moving in the same direction. Not necessarily at the same rates but the trend is consistent across both so I don't think there's any major measurement error.

What could be going on here?

1. I still have air in the system somewhere and my bleed technique needs work!

2. Thermostat is on the way out

3. Head gasket failure

At a bit of a loss now so would appreciate some advice.

Thanks,

Sam

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Yes, you could still have some air in there. You could add massaging the hoses to that technique. Or it might now be time to drill a hole in the thermostat... and some Members recommend that anyway.

You can check if the thermostat is opening by feeling the external temperature of the hoses as it warms up.

Do the coolant and the engine oil both look normal?

Was any work done to it just before it went into storage?

And is the radiator fan blowing in the right direction?

Jonathan

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Thanks for such a quick reply.

1. What does drilling a hole in the thermostat do - make it open sooner as closer to ambient temp?

2. I will check that the hoses change temp as the car warms up.

3. The coolant looks pretty good - nothing out of the ordinary.

4. The car has had a bit of work recently:

- The engine oil was replaced a month ago. The level is correct - checked when engine is hot and running - 5W50.

- I had the cam timing perfected and the belt changed 2 months ago by DVA.

5. The radiator fan I believe is blowing in the right direction; blowing air through the radiator and out the nose. 

 

 

 

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"What does drilling a hole in the thermostat do... ?"

AIUI there are two beneficial effects:

It allows air to pass when bleeding with the thermostat cold and closed.

And it provides some warming of the coolant in the radiator so that the thermal shock to the rest of the system is lower when the thermostat does open.

Picture and fitting hints.

Jonathan

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If you drive consistently without stopping at traffic lights etc, is the temperature consistent?  Has what you're experiencing changed from previously or is the car fairly new to you?

Stu.

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QED_0.pdfHiya Samsul - in essence sounds like a simple fix, - thermostats can get sticky and erratic with age.

I note the very good advice here about the fan direction and thermo modifications, I went a tad further and installed a QED bypass system, and also fashioned a cowling for the rad, and extra fan (manually operated) in front of rad - bit OTT for your symptoms but in sunny AUS it works a treat.

Essentially from my reading the K series is the "car school drop off" type engine, - heat up quickly in cold climate and stay hot to run the systems, in our sevens we need more reliable longevity out of our head gasket/ engines so less thermal shock and more competence on track/ fast road.

It would be interesting to look at the Chinese MG marque engine systems as I BELIEVE they are running a re engineered K series. 

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Thanks for the feedback all.

SLR - When driving consistently the temp is where I'd expect (82-85) and remains stable. The heating up only appears when stopping or immediately after pulling away. And again, this behaviour only starts after around 30 mins on the move; prior to this the temp is stable at lights and when pulling away. This is the part I find so odd! This behaviour is new. I have had the car a year (6,000 miles) and this issue has appeared within the last 100 miles so something has changed but I can't work out what yet. 

Tomorrow morning I am going to check the fan direction, re-bleed the system, check the thermostat is opening, and do another leak-check. Will report back.

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Before doing anything else, fit one of these into the heater/bypass circuit at the rear of the engine. It prevents false readings caused by the manifold heating the coolant rail. This happens when stationary, in traffic etc, but only when the coolant gets warm enough to have an effect.

You'll also need the blanks for the two outlets on the coolant rail (Caterham can supply) and if you have the earlier VDO gauges you need to earth the new pipe by running an earth lead to the threaded boss, later Caterham branded gauges don't need the earth strap.

Stu.

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I had a brainwave on the way home from work.

I haven't used my heater for about 10 months as I suspected a small weep. Therefore, the heater valve has been closed for that time. However, if I had pulled the plunger and opened the valve I may have unknowingly allowed air to enter the system.

I am going to bleed the system tomorrow with the heater valve closed and see if that makes a difference. If it does then I know I definitely have a break in the circuit somewhere north of that junction and will replace as necessary.

 

 

 

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Doh! I should have included that:

1 Bleed with the heater open.

2 Locate the highest point in the run. Consider adding a bleed valve.

3 Check that the heater gets warm. And that the valve is moved by the cable to both fully closed and fully open: it's quite common for it not to be.

Jonathan

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Ok so...

1. The fan is definitely doing what it should. It pulls air through the nose of the car and blows onto the engine. My mistake first time round!

2. On startup there was a single drop of coolant that escaped from the metal junction that houses the heater valve. There may be a miniscule crack in the metal but upon running the car for 15 mins not another drop came out. Hmm.

3. At 82-85 Celsius the coolant pipe running to the thermostat is hot but the pipe running from the thermostat to the bottom of the radiator is luke-warm then cold, indicating limited coolant flow. The temp remained at 80 ish so not sure if the thermostat is behaving correctly?

4. The temp remained stable at 82-85 when run on the jack for 15 mins and as I bled.

5. When bleeding the radiator there is some bubbling as I release the bleed nut. I assume I keep the nut slightly open until there is no more bubbling and only liquid coolant comes out? Should I loosen this nut only half a turn or so?

6. The heater valve definitely moves from fully open to fully closed and the heater works.

Apologies for all the questions - I am learning!

Best,

Sam

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Thanks for the great advice.

I think (*fingers and toes crossed*) things are looking ok.

I bled it again with the cap off the expansion tank and the bleed screw fully removed from the radiator. No burp of air but things improved after this. I then took it to a friend's house and did the same thing again on his steep driveway. The coolant level in the expansion tank dropped when I shut the engine off this time, hopefully meaning an air pocket has now been replaced with coolant.

A quick top-up and a fair bit of blatting later and things look good. The temp rises slightly when I accelerate hard but an increase of only 3 or 4 degrees. The relief for me was hearing the fan kick in at 85 and then seeing the temp drop on the gauge and on the OBD live data. This was not happening this morning; the temp kept climbing even after the fan kicked in.

My gauge is a bit 'sticky' though, in that it is slow to show a reduction in temperature. However, if I switch the readout to oil temp and then back to coolant temp the displayed temperature is then a few degrees cooler. Curious.

Anyway, again, thank you for the help. Much appreciated and managed to have some fun in the sun! 

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Yup sounds like you've got it, any re- occurence I'd definitely swap out the thermo, cheap cheerful and easy fix, with the drop of coolant from the T keep an eye on it, try a  magnifying glass, quick weld would repair it.

Good work! Always refreshing to find the thing and fix it, I have never had any issues with airlock but  a good long run and re check often is the answer.

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Ok final update!

The heater valve is definitely leaking a bit of coolant. This is no longer affecting the stability of the temperature reading but I have a spare so will swap anyway.

I think the two sensors on the coolant rail are suffering from heat-soak at different rates. When stationary, the ECU readout will continue to rise up to 180-185F (roughly 85C) long after the dash gauge has stabilised at 80-85C. I suspect the smaller sensor that powers the gauge is getting heated-soaked by the exhaust manifold early and then stabilises whereas the much larger ECU sensor takes longer to get heat-soaked. This behaviour was confusing me for a while but lots of testing and fiddling and I can' t come up with a better explanation and suspect this explains some of the odd behaviour I saw re: temp rising when stationary and when pulling away.

A laser heat gun confirms that after a drive the radiator end of the top coolant hose is around 188F and the heater end (above the manifold) is around 220F. The sensors are sat right above the manifold. SLR - I totally understand why you have moved your sensors away from this location and I will be doing the same in time!

Thanks all - I have learned a huge amount and now have a mostly functioning coolant system!

Best,

Sam

 

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  • 1 month later...

Hi,

Looking for a bit of advice on the cooling system again, sorry!

I have concluded that the dash gauge misreads so no longer rely on it. Instead I run around with an OBDII reader plugged in relaying live data.

Based on the OBD readings, the car generally runs between 71C and 77C. I suspect this is a little low but not sure?

On a run last weekend the coolant temps were within usual operating range (70s with the odd foray into the low 80s whilst sat at lights). However, when I pulled onto the drive I let the car idle to see if the temp would peak and then stabilise. Within 2 mins the OBD reading hit 92C before I bottled it and shut the engine off. There was no sign of the temp levelling off.

Interestingly, there is no issue when moving - even at 10mph where there is limited airflow through the engine bay - the temps drop 4 or 5C within 20 seconds of moving off, even at extremely low speeds.

This is a long-winded way of asking if  (a) I am simply being deceived by my sensor getting heatsoaked and I need to stop worrying and get on with things! (b) there is yet more bleeding to be done to remove an air lock © my thermostat or water pump isn't behaving properly at idle?

As background, I have back-filled the heater hoses, filled the radiator to the brim, massaged the pipes, all with the nose jacked up as high as possible.

 

 

 

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