Engine temp

Engine temp

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Discussion

Jooles81

Original Poster:

127 posts

148 months

Saturday 18th March 2017
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Hello!

I took the beast for the first real drive of the season, and though it was flawless, the engine temps are behaving Strangely.

The car never overheated, but when drive at low load / low rpms, the temperature is higher than at higher rpm / higher load, all other things considered equal. For instance, 40mph on 4th gear was hotter that in 3rd.i I'm talking a few degrees difference (4-5) but it was still noticeable. On the same note, when getting the car back in storage, the temp struggled to get down with the fans on. Outside temp was 17C today, so not too warm, and the water temp was between 75 and 90 depending on the conditions.

The car has had a thermostat change before storage, and I suspect a poor quality coolant to be the origin of this behaviour. Before this, the thermostat was always open and the temp were decreasing much faster at idle with fans on than before, even with 35C outside.

Thanks!

Julien

mike_e

584 posts

262 months

Saturday 18th March 2017
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It's more to do with flow through the radiator. In 3rd gear versus 4th the pump is spinning faster so more water flow through the radiator. Similarly, at higher road speeds more air flow through the radiator = more cooling effect. If you've had a thermostat change make sure there aren't any air locks in the system, Cerbs aren't the easiest cars to bleed.

aide

2,276 posts

163 months

Sunday 19th March 2017
quotequote all
The best way to get a better understanding of what's going on would be to connect the diagnostic app, turn on logging and go for a drive.

The log is a timeseries csv file that not only contains realtime data for every sensor, it also logs speed, altitude, acceleration, lateral G plus latitude & longitude.

Open the log with excel and graph the temperature and rpm against time.





gruffalo

7,509 posts

225 months

Sunday 19th March 2017
quotequote all
One other thing to check is the coolant levels, if it is a bit low you can get behaviour like this.


Jooles81

Original Poster:

127 posts

148 months

Sunday 19th March 2017
quotequote all
Thank you for your answers!

I don't think there may be air in the system. I've driven in several times, and the coolant level does not move. Am I right?

Aide, I've used your app to monitor the temperature, but did not make any log. But the temp really decreased a few degrees when getting one gear down. It's not so fast to move though.

Grufallo, you may be right (well, I hope so!). I know it should be lower than what written on the tank but is this OK?




Thanks!

Julien

gruffalo

7,509 posts

225 months

Sunday 19th March 2017
quotequote all
Yep that looks fine, did you bleed the coolant rails on each head?

Jooles81

Original Poster:

127 posts

148 months

Sunday 19th March 2017
quotequote all
Yes, I've bled both sides. But I have not put the nose of the car up. I think I have to do it again properly...

Thanks!

Julien

gruffalo

7,509 posts

225 months

Sunday 19th March 2017
quotequote all
It could well be flow related then, when mine gets proper hot revving it to 2k or so helps bring the temps down a few deg.

Jooles81

Original Poster:

127 posts

148 months

Sunday 19th March 2017
quotequote all
Interestingly enough, the limit for mine was 2k rpm. Would it be normal then?

Julien

gruffalo

7,509 posts

225 months

Sunday 19th March 2017
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Sounds quite normal to me.

ukkid35

6,138 posts

172 months

Sunday 19th March 2017
quotequote all
When the amount of coolant in the system drops, the place where it is evident is the radiator.

Open the bleed cap on the rad and let any air out, and then check the level in the expansion tank.

Jooles81

Original Poster:

127 posts

148 months

Sunday 19th March 2017
quotequote all
Engine running or not?

Julien

ukkid35

6,138 posts

172 months

Sunday 19th March 2017
quotequote all
Engine off.

Most cars have a line from the top of the rad to the expansion tank so that the rad bleeds automatically. The Cerb does not.

Jooles81

Original Poster:

127 posts

148 months

Sunday 19th March 2017
quotequote all
Ok, thanks. I'll check this. My car has an alloy rad, and the bleeding screw is not at the highest point of the rad. There is probably some air trapped there...

Julien

Byker28i

58,826 posts

216 months

Monday 20th March 2017
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Jooles81 said:
Yes, I've bled both sides. But I have not put the nose of the car up. I think I have to do it again properly...

Thanks!

Julien
Nose down, rear up, bleed off the water rails at the rear of the engine usually. Isn't it?

NuddyRap

218 posts

102 months

Monday 20th March 2017
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If you do nose down, rear up, your first point would be the rad bleed screw as that's the lowest point.

When that streams coolant, bung it up and bleed the rail furthest from the expansion tank.

Then do the nearest.

Then top it up to max in the expansion tank.

Start the car with the cap off and bleed the coolant rails until all air is gone. Keep the tank topped up.

Leave running until thermostat opens (~ 80°C), top up and replace cap.

Let the fans cycle a couple of times.

Leave it to cool.

Check when cool.

Check after first drive again.

gruffalo

7,509 posts

225 months

Thursday 23rd March 2017
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Any progress OP?

Jooles81

Original Poster:

127 posts

148 months

Thursday 23rd March 2017
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Not much, but there was air in the radiator, for sure. Not much, but some. I have to buy a jack (which means driving 100km to get a shallow one) to lift the side of the car a bit to need it properly. Should get the jack this weekend, but not sure when I can do it...

Julien

billynobrakes

2,675 posts

264 months

Friday 24th March 2017
quotequote all
Julian
Just read this and its normal for the temp to get to 90 even 95 as that's when the fans are set to kick in so nothing to worry about AJP Engines tend to run hot, as I remember the bleed screw is on top of the Rad its a small Allen key type one.

I have had to bleed the system when I put the silicone hoses on and it can be a sod to do, this is how I did it, I got a really big funnel that fits tight inside the expansion and I mean a really big funnel, filled the funnel right up to the top, then let it drain down naturally then filled it right up again till it stopped draining, then I opened up the bleed screw on the radiator till air stopped coming out you will know when that happens as when the air comes out it sounds like your farting and when that stops I fill the funnel up again right to the top, then I open each bleed tap on the water rails and repeat the process till air stops, then I fill up funnel again and then start the engine so water gets all round the engine don,t let the engine get too hot as I repeat the process again till the water in the funnel stops draining and no gulps of air is seen in the funnel. I then put cap on expansion tank and let the system pressurise by starting the engine again don,t let engine get too hot as then I undo cap on expansion tank while the engine is running this should then purge it much in the same way as you do on a Griff engine, I have never had to jack it up at all.

Don,t forget I had the Cerb 17 years and have changed the hoses along the way and the Rad

ukkid35

6,138 posts

172 months

Saturday 25th March 2017
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The Joolz remap includes a change to the temp that the fans kick in. However I decided not to have that done when he remapped mine, believing that it could possibly mask an underlying problem.

I think that was the wrong decision, so I will ask for that option next time I see Joolz.