engine temp issue

[Jed the Fred]

Whats up guys. Just recently I've noticed my temp gauge on my cluster has been reading hotter than usual. Before it was at halfway now its reading 3/4 hot. Even though idle and driving. Even sometimes it will hop to fully hot and then jump back after 5 seconds or so. I usually just turn on the heater to cool it down.

Is it a fan clutch issue? Would an electric fan conversion be worth it? Thanks guys.

[monty23psk]

you need to look into this ASAP. If the sender or gauge are OK and that is the real reading, then you can risk cracking the head on the m42. These cars can overheat in the blink of an eye. I would start with the fan clutch. Do the temp go back down while moving, for example at highway speeds? If so, it looks to be the clutch. Then you can decided if you want to go electric or keep it stock. I have electric and it is very important the cooling system is running at 100%. The electric fan can only help so much.

[bmwman91]

If the gauge is literally jumping around, then it could be a fault in the temp sender or the connector. I have heard that the wire has a tendency to break near the sender plug.

If it is slowly creeping up and down, and it is vehicle speed related, then I second that it is probably a failing fan clutch. You need to address this ASAP.

monty, does hitting the 3/4 mark run much risk of cracking the head, or is that generally OK?

[Jed the Fred]

you need to look into this ASAP. If the sender or gauge are OK and that is the real reading, then you can risk cracking the head on the m42. These cars can overheat in the blink of an eye. I would start with the fan clutch. Do the temp go back down while moving, for example at highway speeds? If so, it looks to be the clutch. Then you can decided if you want to go electric or keep it stock. I have electric and it is very important the cooling system is running at 100%. The electric fan can only help so much.

I just went for a drive. At idle it climbs slowly but once I start driving it goes back down. I did notice my fan too. Visually it looks like it doesn't spin fast like a normal fan would.

[monty23psk]

monty, does hitting the 3/4 mark run much risk of cracking the head, or is that generally OK?

From your post with the MM engine and radiator issues, you should be fine. unless, in lives there all the time for a long period of time. Too much heat can cause the metal to soften and eventually causes a hairline crack which is just enough to bring on the doom. This was explained to me by my engine machine shop which specialize in BMW's, including race engines. Without looking at my head, just knowing it was a m42, he knew of the two locations they crack. Sure enough it was in spot one. He then said if they repaired the crack, next time it will be in the other spot as the metal had soften already. In my case, it never got to red but got to 3/4 a few times over a period of a month and a little passed a few times, which I would just pull over to let it cool. This was only in stop and go traffic. Car still ran great but in the morning it would have faint white exhaust indicative of head gasket or head crack. I could have kept running it for at least 3 more months until summer hit and then I wouldn't be able to drive it to work or then oil/coolant mix would begin. My fist child was about to be born so I decided to do it right before. Got lucky on ebay to find a spanking brand new BMW m42 head for $400. I believe build stamp of 01 or 03.

[monty23psk]

I just went for a drive. At idle it climbs slowly but once I start driving it goes back down. I did notice my fan too. Visually it looks like it doesn't spin fast like a normal fan would.

Sounds like fan clutch to me. Stick a rolled up newspaper in the fan while engine in idle and if it stops fan without really tearing paper, the clutch is shot.

[Dj Buttchug]

you have to get an m42 head roasting hot to split one. yes other issues can cause cracks but 3/4 hot is not going to crack the head.