Random check coolant warning
 

My new-last-winter coolant tank is now very occasionally popping a “check coolant level” warning. It’s clearly in error as the tank is always full when I check.

Before I throw a sensor at a new tank though, I wanted to check to see if there was anything else I could be missing. Thanks all

Is the magnetic float not moving freely?

Check the connector wiring harness. Mine had a random alarm. It finally stayed on. I swapped two tanks too. One wire had broken off. I depinned it and repaired it. It's been fine since then.

Float is bobbing freely, but I’m wondering if the sensor in the bottom of the tank is going bad? I can’t recall if that sensor that plugs into the bottom of the tank came with my new tank last year, or if I reused the old one. If the latter, then it could definitely be going bad.

I did a Quick Look at the wires leading to it and they look decent, but I’ll do a deeper dive for breaks and shorts.

I finally caved in a bought the 90 deg MAP t-stat from ecs, or FCP, can’t recall, and will pull the tank/ check the wires and replace the sensor all at once when I do the tstat job.

I’ve been logging my temps around town and on the highway for the past few days as I want poins of comparison when I replace the tstat. The engine coolant should be roughly 15 degrees cooler on average, but I believe that heat has to go somewhere in the closed system - the radiator. It seems the critical number is the spread between the engine coolant temp and the radiator outlet temp, at any given time. I would expect that spread to decrease by 15ish degrees with the new tstat. Normal around town and easy highway driving in the summer here gives me a spread of 60 to 80 degrees. Hard acceleration and/or driving drops that to 30 to 40 degrees temporarily (MAP not activated). I’ve seen as low as 20 degrees of difference between the radiator outlet and engine coolant temps under heavy acceleration and MAP cooling on, on a hot day.

My basic concern with a lower tstat is that the cooling capacity of the radiator will be tapped out, should it ever need it. Likely not with just a 15 degree lower tstat hopefully. It will be interesting to see what the numbers show after I install it. I’m also interested in seeing if I can feel any increase in power in certain circumstances as the DME may not need to dial things back as much in response to impending pre-detonation as things get hot.

Put a jumper in the connector. Wiggle it. See if the alarm goes away. The tank magnet should be fine.

Random check coolant warning
 

The amount of heat a radiator can dump is "other worldly".

They make special radiators for operating in ambient heats over say 40-50c but in normal climates the radiator will dump any amount of heat. Note when a tstat fails open the engine usually can't reach operating temp.

Also interesting to watch how amazingly quick my engine will drop from 108 to 95c when climbing hills or heavy acceleration.

I looked into lower temp tstat until I realized much of the design is meant to be hotter. It does beat the crap out of the plastic parts but I don't know if the small change in absolute temps would make much difference. Eg. If plastic parts lasted 14 years at 368k bumping that down to 363k (1.4% drop in absolute temp)

Yeah, I’ve gone back and forth on the tstat change, but finally figured that it was worth a try, if only as an experiment. I think the power sapping result of running these cars so hot is a decent enough reason to monkey around with it and see how it affects things. Plus I like a project, and I’m a bit short of cash right now for anything significant on the E53, having just bought my wife the G05.

We sold my daughter our 2015 Grand Cherokee which has been a good car, and should be a reliable first car for her for several years at her first job and commute. I also just donated (today) my 31 year old Grand Cherokee which actually made me tear up watching it leave on a flatbed 15 min ago. 250k on the original 318 and transmission, but it was failing and needed significant money for suspension, transmission and other “safety of flight” work. It had been relegated to being the rescue car for the E53 occasionally over the past few years. Sucks to see the ones you like go, however.

https://i.postimg.cc/RZcK9TQc/PXL-20...5-Original.jpg

Down to two cars for the first time in a long time.

https://i.postimg.cc/W4Tr4JXx/PXL-20...0-Original.jpg

Time to start thinking about that next BMW project in earnest….

I think we are on a similar mindset for the why not temp change. I think the only real offset will be mog for more power tradeoff.

E53 takes enough fuel that I doubt you'll notice much at the wallet.

I'd be curious to see the before and after.

Me too. I’ll keep track of it and post some before and after data points here. It’s not going to happen within the next few week…hopefully in August after we move recently graduated Thing 2 up to VA to start a job/real life.

As much as I’d like to take it, the e53 will sit this road trip out, in favor of the new 50e x5. I am going to park it in the employee parking garage at the airport, several floors up while we are gone. It’s only the end of June and there is a monster storm spinning up in the Caribbean already. Ugh