free hit
counters
87 Excel SE Engine temperature and AC - Engine & Ancilliaries/Gearbox - The Lotus Forums Jump to content


87 Excel SE Engine temperature and AC


Recommended Posts

So I have a somewhat puzzling temperature issue. 

The car is not overheating, but when the AC is on it has trouble getting rid of heat. If it gets to say 97C, with the AC on it will stay up there. Turn the AC off and it will drop right down. The AC does not make it run particularly hot, but once it gets there, you have to turn it off to get it to come down. 

I put in the lower temp thermostat today, didn't do much. Took it out for a blast on the highway today about 80F out, AC on. Got on it and got the temp up to 92C or so. Got off the highway temp stayed the same. Idling in the driveway stays the same. 

Turn the AC off and it visibly quickly drops and cycles with the fans to 84-88 degrees C

I am not surprised it running slightly hotter with the AC on, it is the behavior. My Exige runs maybe 5 degrees hotter across the board with the AC running

The other day I stopped briefly , and on restarting it was very nearly 100 C, and would not pull down until I shut the AC off. 

 

I mean, if the AC compressor were on the same belt as the water pump it would make more sense to me. 

Ideas?

Link to post
Share on other sites

Upgrade today to remove Google ads and support TLF.
  • Replies 15
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

If you find the gauge is working correctly maybe your radiator needs attention - it has to cope with warmer airflow from the condenser when the a/c is on. Pete

I would do a thorough internal clean of the cooling system with something added to the coolant and a good flush.  Any improvement might indicate that the radiator isn't as good as it looks. Pete

  • Gold FFM

Is water pump belt a tad loose, so when AC on, it struggles to keep engine cool? I know I had issues with water pump, which from memory was in relation to power steering pump/belt but I forget the exact problem. It cost me a head gasket. 

I assume you engine cooling fans are working when AC on.

Justin 

Link to post
Share on other sites

Different belt for AC than WP & PAS, so shouldn't be related.  If it's a new problem then I'm at a loss but if you don't have a known-good state before then worth checking fans etc haven't been wired incorrectly or have a faulty earth as you could have a fan pushing air forwards when on air-con.

 

Are you judging water temp by the gauge? If so, it's likely a false reading (again may be earth related).

I've had it in multiple Excels where the gauge has a reading, as soon as the fans kick in the needle jumps to a higher indicated temperature (I do mean jumps, as in it bounces it moves so fast) which to me says that with fans operative (which they are with AC) you get a false higher water temp reading than you would normally.

Link to post
Share on other sites
  • Gold FFM

I did understand the belt for AC was not related to WP but I think the WP belts tend to come loose, if I recall it is connected to the PAS system? I just wondered if the WP was struggling, this may manifest itself more when AC on. Probably completely wrong...…….

Agreed re gauges. I take them as guide, not at face value. My S1 Elise temp gauge is all over the place but no sign of any mechanical problem.

Justin 

Link to post
Share on other sites

If you find the gauge is working correctly maybe your radiator needs attention - it has to cope with warmer airflow from the condenser when the a/c is on.

Pete

  • Like 1
Link to post
Share on other sites

It have done fairly extensive work with the gauges. I ended up building a daisy chain 12 volt and ground buss behind the gauges to  stabilize the readings. They read relatively correctly now, although small variances continue

https://www.lotusexcel.net/viewtopic.php?f=27&t=11677

 

I have checked the instrument against a non contact thermometer under the thermostat, before my wiring mod, and it was predictable even with the error

 

The fans run correctly and in the correct direction, new relay installed recently, and if it was an issue that was fan related I would expect it to disappear once moving over 25 mph, but it does not. 

It is puzzling again for its almost total relation to the AC and how instantly it responds to shutting the AC off.

 

 

Link to post
Share on other sites

Remember the A/C condenser is Infront of the radiator and so pre heats the air before it passes over the radiator and the hotter the day the worse it is.

So the thermal load from inside the car plus the heat of compression by the compressor and the fact the ambient is high will make the radiator far less efficient than it normally us.

So instead of getting air to the radiator at say an ambient if 28'C after it's been through the condenser it's probberbly nearer 43'C 

Link to post
Share on other sites

I understand that, but it is my feeling this exceeds that effect, and does not appear to be directly related to outside temperature. Could be I am chasing my tail, but it does not seem 'right'

Link to post
Share on other sites

Are you fans 2 speed ? as the A/C and coolant control for the fans react with each other.

So if the coolant is at 97'C and the A/C's s running the system of control will proberbly only allow the fans to hit the second speed if the coolant temperature rises as to do so would now possibly cool the A/C condenser to much and thus over condense the refrigerant which in short lowers the discharge pressure to much and upsets the flow of refrigerant around the circuit.

That's the problem of having one set of fans cooling two different circuits so there is always a compromise.

In cooler weather the radiator thermostat can close if the fans are running for the A/C but the A/C usually hasn't any way of reducing capacity other than turning on and off (expensive compressors in top end cars do have an active swash plate than can react to suction vapour pressure but that's another story for another day ) so as long as the engine temp is within operating conditions the fans usually then look at the condensing pressure for the A/C and only become overridden if engine temps rise to much 

 

Link to post
Share on other sites
  • Gold FFM
23 hours ago, andydclements said:

I've had it in multiple Excels where the gauge has a reading, as soon as the fans kick in the needle jumps to a higher indicated temperature (I do mean jumps, as in it bounces it moves so fast) which to me says that with fans operative (which they are with AC) you get a false higher water temp reading than you would normally.

The gauge in my Esprit SE does exactly the same thing. The fans do account for an extra current draw, but I'd expect the feed for the gauges to be stable enough to deal with that. And other big electrical loads like the high beams don't seem to have any effect at all. I can't find a common point in the wiring that could explain it either.

Filip

I have made many mistakes in my life. Buying a multiple Lotus is not one of them.

 

Link to post
Share on other sites

It is not instrument error. I have double checked as recently as this afternoon with a non contact thermometer and the reading for just below the thermostat is essentially identical. 

 

The fans run together[by design] and the correct direction

The water pump was replaced by the PO's shop 10000 km ago. 

The AC condenser appears newer[painted black and newer than the brackets]

visible part of the radiator appears in good shape.

If you start it and idle it it will eventually come up to temp and run to the fan thermostat at 84-88C back and forth

Today it was in the mid 80s F[29C]

I went to the post office, downtown driving, let it idle outside, maybe 90C 

Drove in some traffic, and out a slowish country road, stopped for a construction project and cruised along, and it reached 102 C or so. Shut off the AC and it quickly dropped

After work I drove out onto the highway at ~120kmh,  heading towards warmer area, solid 88C

Turned around at an interchange,two stop signs up to 95C. Back on the highway quickly down to 92C, slowly by the time I returned to my exit it was back down to 88C

 

 

My thinking:

Were it the radiator old, clogged etc, it would have trouble on the highway as it is creating power and a bad radiator would not be able to get rid of it 

While it might be an undersized radiator it does not seem to be the problem

 

I am leaning towards the fans being crap. 

They 'work' but it is not like they blow your hair back 

Perhaps newer style fans will work the way they should.

 

My +2 has a new style fan and once I forgot to turn it on when the thermo switch had died, and it pulled it down from 110C to 95 in a few minutes

 

 

 

 

 

Link to post
Share on other sites

I would do a thorough internal clean of the cooling system with something added to the coolant and a good flush.  Any improvement might indicate that the radiator isn't as good as it looks.

Pete

  • Like 1
Link to post
Share on other sites

running caustic chemicals through my Lotus block is not my first choice

The radiator does not look OK,  from the small window one can see past the fan, it appears new. Like not even dirty. Well, I did flush some water through it in case there was mud or something that I could not see. Fins still have paint on them. The car has no evidence of sitting or lying fallow or getting run down. It is of course possible.

 

Link to post
Share on other sites

Interesting case, this, just went through the thread and re-read the ppening posting. The correlation between AC and temp levels seems clearly established, suggesting marginality in the system. Water pump belt condition does not shift in accordance with the heat load so I'd set that aside for the moment. If the AC seems to be functioning well in its own right then it should be rejecting a normal measure of heat into the rad, so again to be set aside. Begs the question whether rad and/or ducting are fully up to spec. I believe it vital to ensure air admitted for cooling is tightly managed by way of ducting. Sub-optimal setting thermostats are not the way forward, other than for brief explorations of dubious value. By the way, heat rejection by way of the rad should improve slightly at higher temperatures as the gradient to ambient is greater.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.




×
×
  • Create New...