Underheating Engines...

"Orange Exige" (OrangeExige)
04/28/2016 at 19:43 • Filed to: r53, help, troubleshooting, underheating, p0128

Hey guys, just trying to get a little more information on the topic of underheating engines (yes, on my R53 Mini pictured)...

(optional read:) Long story short - had it for a couple months, CEL threw the !!!error: Indecipherable SUB-paragraph formatting!!! code - not coming to operating temps quick enough (or at all). Also had the occasional cold start issue. Normally, such an issue points right to the thermostat buttt I was told by the previous owner (I will remain civil and not comment more) that he replaced the thermostat with an OEM one within the past year so I went with option #2: coolant temp sensor. Alas, I went with a NAPA Echlin part instead of OEM but it actually fixed the “real” problem with cold starts. CEL turned off eventually on its own but then turned back on and was basically on all winter and up until now, even in the warmer weather.

Anyway, what I really want to know is this:

Normal operating temps are supposed to be around 90°C and in recent normal commutes (15-20 min, decently warm weather), I’m noticing a seemingly normal warmup time but the running temps stay steady at 78° (hence the CEL). Now it’s possible there is a cooler thermostat in there that I don’t know about (which would explain a lot), but is it actually likely that a stuck-open normal 90° thermostat would prevent the engine from getting over 80° in normal operations??
I would think that a stuck-open thermostat would take longer to come to operating temps but eventually it would still get up there given enough time. This is not happening here - it’s a steady 78° +/- 2°.

Thanks!

DISCUSSION (14)

Steve in Manhattan > Orange Exige
04/28/2016 at 19:48

Almost always in these cases the answer is thermostat. Is the housing cracked? Any puddles? These are all Car Talk answers - haven’t wrenched my own cars since the early 90s.

4muddyfeet - bare knuckle with an EZ30 > Orange Exige
04/28/2016 at 19:48

Have you tried making a muff to inhibit air flow across the radiator to see if you can increase the coolant temp?

Highlander-Datsuns are Forever > Orange Exige
04/28/2016 at 20:09

My mazda 3 had a stuck open thermostat, it would not get up to temp, ever, even on a hot day. On a long downhill it would go down to about 1/10th of the gauge and it is designed for the needle to run right in the middle. Had a new thermostat installed (major PIA on this car) and it had been good ever since. I would put money on the thermostat being bad or not the right temperature rating.

Danger > Orange Exige
04/28/2016 at 20:39

I put my thermostat in upside down once. Truck would never come up to temp. Maybe the PO put it in wrong.

Orange Exige > 4muddyfeet - bare knuckle with an EZ30
04/28/2016 at 20:56

This is a new one to me... so no I haven’t tried that.

Block airflow to the rad with a sheet or something? Not something i’d particularly want to play around too much with (at least on a commute with potentially unknown traffic) but it may be worth a try...?

Orange Exige > Highlander-Datsuns are Forever
04/28/2016 at 21:19

This is something that I was totally looking for - real experience with the issue. Definitely not looking forward to doing the thermostat (regular PIA + I HATE dealing with chemicals like coolant), but at least i’d have more confidence that it’d at least solve my problem.

The PO did do a bunch of performance mods so it’s possible that he put a cooler t-stat and didn’t tell me... but it’s also possible he didn't replace the thermostat in the past year like he DID tell me...

Orange Exige > Danger
04/28/2016 at 21:31

Several months later though?? I had it for at least two months before the CEL turned on...

Danger > Orange Exige
04/28/2016 at 22:18

Yeah, that’s odd that it just started happening. Rereading your post and the other comments, a low temp performance thermostat seems likely. I also had an old Grand National with a 160F thermostat, and on really cold days it had trouble getting up to temp and staying there, causing an intermittent CEL.

Ilike_cougars > Orange Exige
04/29/2016 at 11:11

Did you check the coolant temperature sensor?

DynamicWeight > Orange Exige
04/29/2016 at 12:20

“I would think that a stuck-open thermostat would take longer to come to operating temps but eventually it would still get up there given enough time.”

If that were the case, then the car would almost always have just barely enough thermal dissipation to barely keep the engine at correct operating temperature. Any increased load at all would overheat it. So no, a stuck open thermostat will be able to continually cool the engine more than it is supposed to. I would think the needle would be jumping around a bit though, like it would get warmer as you sat at a light for a while and then drop as you start moving.

When the thermostat was replaced was the coolant flushed? If not, perhaps the dirty coolant has gummed up the new thermostat. If you can do it yourself, just replace it. Thermostats are cheap.

Orange Exige > Ilike_cougars
04/30/2016 at 09:27

I actually replaced it months ago as the expected solution since I was more confident the thermostat had been replaced recently and that is culprit #2.

I couldn’t find any specs online to test it to see if it was actually a problem but considering it fixed my cold start issue, i’d say it was (at least part of the problem).

I also did now know at the time how to access the diagnostic menus so I don't know what coolant temps my car was reporting like I do now :/

Orange Exige > DynamicWeight
05/09/2016 at 14:56

Did I thank you before? Idk so thanks (again) pal - turned out to be a stuck open thermostat indeed (cue the head nod) and whaddya know, we’re back up to operating temps with a new t-stat and coolant.

Orange Exige > Highlander-Datsuns are Forever
05/09/2016 at 15:10

In case you were curious, it turned out to be a stuck open t-stat causing the issue. It actually was the right temp, seemingly oem as well, but whether it was as new as it was claimed to be... well, who knows?

Wasn’t the worst install in the world luckily - but MINI wanted to make it really difficult to properly drain the coolant which kinda sucks. After an initial drain, refill (to flush) AND a second drain, I just got 6 liters out when there was supposed to be 6 liters in the system (meaning I SHOULD have gotten 12L out from two drains...)

DynamicWeight > Orange Exige
05/09/2016 at 16:21

Congrats on a properly functioning vehicle! I’m stoked it was an easy fix.