Why would the temperature of the air blowing on the radiator now impact how well the system can cool the coolant and the engine? I might agree that a difference of 20 or 30 degree in the air temp might not make a difference, if that is what you meant.

So where does this leave me? Poor flow for some reason?

What temperature should the engine be? I can see if the engine is running hot? It night be because i know I have a crack somewhere in the intake side and I am getting the occasional Lean Bank error code. I also have a leak in my valve cover gasket.

3.0 motor should be about 90-95° normally.


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There are many X5's running around in the desert with ambient temps above 120F and they do not overheat so my point is the tunnel temperature has nothing to do with your issue.

The thermostat would be the first component I would validate. So you will need to get an exact reading on your temps. The stock gauge will show straight up anywhere from 75C to 115C so you need to not rely on that.

There are several ODBII apps you can install on your phone that will take a simple OBDII interface plugged into that port or you can get the temp through the hidden menu.

My advice would be to get the OBDII interface as it will have the ability to look at live measures, CEL codes and the option to clear them.

https://www.obdsoftware.net/software/obdfusion

yes, I have an OBDII scan tool in the car, never used it to read engine temp, just to clear and review the occasional code. yes, makes sense what you are saying about cars in the desert etc, but if I have restricted flow then perhaps a 30 degree change in temp would make a difference. thankyou for your help and support, really appreciate everything for all of the community.

Getting a problem to repeat is the best way to find out the cause

that might quickly become a reality as summer creeps in. My car might overheat or run hot once the temperature here goes up... its no coincidence that the same issue happened twice at the same place on warm days, with very hot air in the tunnel. I agree that for a normal working system, the hot air should not be an issue. I might swap out the thermostat and then see how things progress. Will take some engine temp readings first and maybe try and fix my lean bank/valve cover gasket too (before the summer comes) - its just I have virtually no free time in June, eh...

Most spring days in the northeast will have close to a 20 degree swing from day to night. I would think if that was the problem, you would see it every day.

How many miles on the X and given the traffic in NYC I am wondering what kind of speeds you were traveling before entering the Lincoln Tunnel and how fast in the LT?

Thermostat or viscous fan clutch would be my best guess. :dunno:

BTW, I had a 1992 348 TS. Loved that car

it was a long ride home in traffic for like 2 hours... in the tunnel it was slow, crawling, like 5 MPH. car has 145k on it, I replace the tstat two years ago b/c it was stuck open. when i pulled out of the tunnel, I parked it and checked to see if the main fan directly in front of the radiator was blowing - and it was. hmmm.

Counter intuitive but next time it does that turn the heat on full blast, sorta sounds like you may have air trapped in the system.


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It's not an air trapped thing. If the electric fan kicked on indicates that the output temp is hot and registering.

I'll bet on the t-stat


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