Overheating?

[True Brit]

I was driving home tonight, a warm evening (for England anyway), doing about 85mph at 4000rpm (or thereabouts...difficult to tell with my highly optimistic speedo & rev counter), and I noticed that the engine temperature was rising, and the oil pressure was dropping - not a huge amount, but more than I've had before.

Let me give you some figures. The engine temp went up to about 200, and the oil pressure dropped to about 55psi at 4000rpm. Normally I'd expect it to be about 180'ish, and the pressure about 70psi. Not outstanding, but ok for an old car.

Anyway I dropped back down to about 3000rpm and coasted home, and the temp dropped a bit but the pressure stayed low. Now, I'm overdue for an oil change, so I thought I'd better do that before I took her out again, so while she was hot I drained the oil and checked the drain plugs. I was a bit worried to find that there was quite a bit of fine gritty sludge stuck to the drain plugs, although no large bits of anything. So, I guess the questions are;

(a) Could the rise in temperature and drop in pressure be because the car was overdue an oil change?

(b) should I be worried about fine sludge on the drain plugs - how large do "particles" have to be before they become a serious problem?

Thanks for anyone's help! I don't want to rebuild my engine!!!

[chrisp]

200 degrees. Mine has been up to 270 (track in super hot weather) and in everyday driving sees about 200 on hot days.

I cannot really comment on the low oil pressure but I wouldn't think that oil that is awaiting an impending change would cause press to drop.

[True Brit]

Thanks Chrisp,

It's not really the temperature I'm worried about but the pressure, and the residue in the drain plugs. Anyone else?

[marcesq]

The low oil pressure could be caused by a bad or failing pressure relief valve. There are two, one on each side of the block.

Don't know what engine we are talking about, but there was an upgrade to one of the valves during the early SC years that was applicable to the 2.7s as well.

Fine metallic powder found on the magnet is normal for an elderly engine.

[billy911]

I think the pressure drop is normal as the oil temp increases. If I jump right on the highway before warming up the pressure can be off the scale then slowly comes down to normal as the oil warms up. If it starts to get warm on the highway the pressure continues to fall below normal if the temp is above normal. (hope this or normal or my car is screwed up)

[Tyson Schmidt]

55psi at 4000 rpm with 200F temp is about right. Especially with an oil change due. 10-15 PSI for every 1000 RPM is a good reference. That equates to 40 to 60 PSI @ 4000RPM, so your right in the ballpark. In Southern California, 210 is a daily occurence in my '72. Back in Washington State, It NEVER got above 190.

Altitude will also cause serious temperature increases, due to thinner air and the fact that you are usually going uphill.

Just how warm of a night are we talking about?

[True Brit]

Well that makes me feel a bit better, both about the pressure/temperature and the fine metallic dust in the oil.

The air temperature was only in the mid 20's (about 80 F), so nothing exceptional there.

I think I just need to change the oil then. Just hope that the new filter turns up this morning...

And if that doesn't work, then I'll check out the pressure relief valves.

It's a 2.4E, by the way. Thanks again, everyone.