Temperature warms up at 70mph in '74 2002

[Joe Barthlow]

Drove a '74 2002 today. idling and driving around town, the temp gage stayed low as anticipated. Then I hit a country road where I pushed it 70mph and the temperature climbed. Also could smell the heat, maybe breaking in a new exhaust. I slowed back to 55 and the temp dropped back to normal. got back into town and it stay low. Ideas?

Im guessing the radiator may not have good enough flow to keep up with the RPMs... or maybe the water pump is suspect... I looked under the hood afterwards and everything appeared OK, nothing leaking.

It's all stock. thanks

 

[Bill 74 3.0 CS]

It might be that you have an air pocket somewhere in the system. This could cause the mentioned change in temperature. The rule of thumb is that the more airflow a radiator gets the lower the temperature is, so as speeds go up, the temperature should stay the same or drop. During my city drives, my temp guage is usually higher than when I am on a freeway.

 

[Joe Barthlow]

It might be that you have an air pocket somewhere in the system. This could cause the mentioned change in temperature. The rule of thumb is that the more airflow a radiator gets the lower the temperature is, so as speeds go up, the temperature should stay the same or drop. During my city drives, my temp guage is usually higher than when I am on a freeway.

that makes sense. My E3 hates city driving, but loves the freeway and country roads. thanks

 

[zinz]

+1 on the air pocket. 2002s are notorious for having air trapped in the coolant system. Incorrect ignition timing may also be the culprit here... Did the engine pull strong at all rpms, or did it drop off at upper revs?

Ed

 

[Joe Barthlow]

+1 on the air pocket. 2002s are notorious for having air trapped in the coolant system. Incorrect ignition timing may also be the culprit here... Did the engine pull strong at all rpms, or did it drop off at upper revs?

Ed

it pulled strong at all RPMs

 

[zinz]

Ok. Retarded ignition advance will cause the exhaust to get hot and power typically drops off at higher rpms.

I had a hot running '75 2002 a couple years ago. It had the original radiator, so I swapped it for a bigger, 320i unit. It still would run hot in the summer... I was finally able to completely burp it and it solved all the issues. Typically you elevate the nose of the car, remove the rad cap, open the heater valve and run the engine to operating temps. Squeezing the upper radiator hose helps burp it.

Very simple test if the thermostat is stuck... with the engine at temp and running.. feel the temp of the upper and lower radiator hoses. If the lower hose is significantly cooler than the upper hose, the T-stat could be stuck. It should be somewhat cooler, but not cold to the touch.

How high did the temp gauge go? Into the red? Normal on a 2002 is "3:00" right in the middle... anything below the red is actually okay, but it really shouldn't move too much if the system is functioning properly.

 

[Joe Barthlow]

idling, driving around town and up to 55 mph, temp gage would be about 4 o'clock. faster, around 70 mph, it climbed to 2 o'clock, but not into red. then I slowed back to 55-60 mph and it was back to 4 o'clock. back in town and idling before shut off was still at 4 o'clock.

to my limited car knowledge, I'm thinking timing (most of my mechanical background is from smaller displacement Italian 2 stroke motors haha). The radiator is original so it gets looked at either way.

 

[zinz]

2;00 on the gauge is no problem, but it really shouldn't swing so much. I bet if you flush the system, add new coolant and properly burp it, she'll run just fine.

Are you looking to buy it, already bought it, what's the 411?

If you are new to 2002s, you need to get over to bmw2002faq.com You will find allllll the answers to your 02 questions over there. Use the Search feature and also dig around in the Articles Section for technical writeups for most of the major systems.

Ed

 

[Joe Barthlow]

very likely to offer on it tomorrow. thanks, I'm pretty excited! I like the idea of roll up windows and a carburetor better than electric windows and fuel injection

 

[zinz]

The 2002 is a ton of fun and extremely easy to work on and accessorize. So much good info on FAQ to keep you motivated, too.

Lots of 2002 folks in your neck of the woods that can help with parts and such.

Make sure you check for rust in the rear shock towers and strut tops. Rust in the subframes is another bad spot. 2002s are easier to repair than an e9 as far as rust goes, but it's best not to buy a rusty one...

Send pics if you'd like.

Ed