odd problem... - United Bimmer Community

craig · 05-18-2007, 01:17 PM

last weekend i took my pickup out of town, had it setting at 3K(65) in forth gear for about 15 miles, looked at the guages and my oil pressure was wwwaaayy above high and it was starting to over heat. then i slowed down to 2K and after a while my oil pressure went back to normal and the temp started to go down. iv taken it out of town many times before and it has NEVER done that and dad and i cant figure it out. any ideas?

witeshark · 05-18-2007, 01:20 PM

It's a guess, but maybe the engine was too stressed at the time and the heating of the oil caused the pressure increase

**xsperf** · 05-18-2007, 01:26 PM

oil pressure is supposed to increase at higher RPM so that really shouldnt be a problem(yes, even if the oil pressure is high).. but the overheating thing is tricky, it could be your thermostat, you could be low on coolant, you could have air in your system...

let me ask you, when you are driving normally, does the engine quickly come up to normal temperature and stay there at the same spot every time or is it kinda all over the place, but never overheating?

craig · 05-18-2007, 01:45 PM

i know the oil pressure gets higher when the rpms get higher, but it usualy stays in the middle, it has never been above high. and the temp guage always stays in the same place after it gets warm unless i let it idle for a long time, then it starts to get hot. its the first time its overtheated like that while i was driving down the highway

**stevo** · 05-18-2007, 02:55 PM

Do you have electronically, or thermostatically controlled engine cooling fan, if so was it kicking in?
possible sticking thermostat, as above, air in cooling system or low coolant , if you have viscous cooling fan is it working correctly.
is it possible that your radiator cooling fins could be blocked causing restricted airflow?

**xsperf** · 05-18-2007, 10:19 PM

yes, since your car overheats at idle, maybe your aux fan is not working, and when you are at 3500RPM it needs to turn it on, so i would check that

craig · 05-18-2007, 10:45 PM

my fan is on all the time. the only time the fan goes off is when the engine is off. all old cars do that. have any of you driven a v8 car made in the 70's? they all get hot at idle. or atleast, all the ones iv driven and my parents have driven. my coolant is fine, i checked it a bit ago. i dont know wtf is the problem.

**Dudesky** · 05-19-2007, 05:07 AM

I've had a few V8's built in the 70's and 80's, and they didn't do that. If the temp goes up, there's definitley something wrong. Especially for an older engine like that- they're usually bulletproof and made quite simple. Your fan may be spinning, but you have to check if the fan clutch is working. Yes, as long as the motor is running it'll free spin, but if the clutch isn't working, then it's not spinning at the same rpm as the motor. Once the motor is nice and hot, try stopping the fan with a newspaper (BE CAREFUL!). If it stops, then your fan clutch is shot.

Moreover, have you ever had the coolant flushed and changed? It sounds to me like the coolant is not reducing the engine temperature. At higher rpm's, the coolant cycles through the system so fast- if it's no longer effective in lowering the boiling point, then it won't draw the engine heat away as good as it used to.

Now, this is for the cooling end of things, I don't know how that impacts or has anything to do with the oil pressure.

**c1apton** · 05-19-2007, 05:09 AM

replace the alternator belt (it also runs the waterpump) it sounds like your belt is glazed causing it to slip through waterpump pulley at higher RPMs causing wp to spin slower. Also change thermostat & gasket and replace thermostat w/180 degree, on older vehicles the thermostats are waxed filled and a "good overheating" damages the wax pellet internally (cheap insurance)
(I highly doubt he has a fan clutch on that "old girl")

**TerryY** · 05-19-2007, 11:38 AM

Have you hosed out the radiator lately?

Dust and mud from you field plowing can collect pretty quickly.

Bugs are another good source of clogging the airflow thru the fins.

Don't forget the A/C condenser if you have A/C.

See I have not forgotten all of my Youth among the fields.

craig · 05-19-2007, 10:11 PM

i did notice some grass in the radiator a few days ago, didnt think anything of it. ill clean that out and see what happens.

**Jimmie34** · 05-27-2007, 02:34 PM

Not the cause for over heating but if the engine is hot enough although rare on an old engine the oil pressure regulator may hang causing high oil pressure. A contaminate could stick it also. When was the last time you changed your oil. c1apton has a great idea on checks for overheating.

craig · 05-27-2007, 07:24 PM

i changed my oil three weeks ago. it hasnt been giving me troubles anymore, so im guessing something was clogged and pushed its way through. who knows.