K-Series engine temp rising

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Jonathan Kay
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"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."

Good plan.

Jonathan

 

samsul
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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.

 

 

 

Jonathan Kay
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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

Jonathan Kay
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But how about the direction that the radiator fan is blowing... ?

Thanks

Jonathan

samsul
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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

samsul
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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! 

timb2117
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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.

Jonathan Kay
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Well done.

Jonathan

PS: If that gauge issue gets any more noticeable do let us know.

samsul
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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

 

Wrightpayne
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If the heater is the plastic type with the seven logo embossed in the front then the heater valve is from a London Taxi.

If the system is not pressurising fully due to the leak then it will not be working at optimal performance.

Good progress so far!

 

Ian