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Old 12-22-2010, 01:31 PM   #1
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Causes of Overheating M42

I am looking at buying a 1991 318iS and the seller is saying that it occasionally overheats.

I am just wondering what that could be? I know the list is long but I am wondering if someone with some experience with these cars/engines knows of any common problems they have?

I did a search and a lot came up about them overheating, but I am sure that's the case with any car this old. I did not find anything about serious issues though.

The car has 200,000 miles on it as well... Maybe I should stay away for that reason alone?
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Old 12-22-2010, 03:05 PM   #2
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Could be thermostat stuck closed, fan clutch not working properly, loss of coolant due to head gasket being damaged, radiator/hoses/expansion reservoir leaking etc.

If you want an m42 car with that kind of mileage then pay close attention to what kind of shape it's in - is the engine bay a total unkept mess? Is it leaking oil? Can you hear the timing chain rattle when you rev the engine? Does it make any weird noises from the timing case area? M42s can be in bad shape at that mileage - the oil pan tends to loosen off decreasing oil pressure which causes everything to wear out faster. Also the timing chain guides deteriorate, the chain tensioner needs to be replaced periodically, your cam sprockets may be worn out causing the chain to be loose etc. Because it's a more modern engine than the m20, any components that need to be replaced are more expensive. It IS a lower maintenance engine though.
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Old 12-22-2010, 04:09 PM   #3
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Thanks for the info.

I have read that the fan clutch is often a problem but I am just worried that it is something more serious.

I wouldn't have too much of an oppertunity to inspect the car before buying it. It's from the U.S.

The body is in good condition and it's selling for a good price so even if it is someting major it will even out in the end. Maybe I will have it inspected before I buy it.
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Old 12-22-2010, 04:44 PM   #4
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These motors love to be revved!! You just have to make sure your oil level is constantly up; overheating issue? not really. Ive owned one for 7 years. The only time I had overheating issue was when the aux fan wouldn't come on in hot whether while having a/c on. The temp gauge would climb. The only other thing with my other one was air trapped in block when I changed the waterpump and thermostat. Once bled properly it was fine. Ask for maintenance records. Front cover gasket should have been changed - design flaw. This was updated to fix problem. if the motor was run low on oil and car was beat on then you may have worn timing chain or sprockets. Should inspect by removing valve cover. other then this it is a pretty reliable but a bit noisy motor. you can hear it in the cabin of the car. They all - including 325 models need maintenance for something that old. but you can bring them back with a little tlc and $$$.

I think I've had 18 bmw's in 6 years.

1 90 325is white - keepin
1 87 325i vert -red - keepin
latest addition 1 88-325is red - parts
latest addition 1 89-325i vert - white -fixin/sold
latest addition 1 92-318i vert - blue - parts
latest addition 1 87 325is blk - parts.
latest addition as of 2013-Gold 87-325is auto! it's a keeper!
KEEPER 88 5sp Vert 2016
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Old 12-22-2010, 07:21 PM   #5
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My M42 would over heat a lot this summer, the culprit was a small leak in the rad which would cause the fluid to run low. The rad was an easy fix ($100 for the rad and about 15 mins of my time) but once i repressurized the system it exposed all the hoses to higher pressure than they'd seen in a while. They leaked and had to be replaced. Shortly thereafter the water pump started to leak.

I say this just so you keep in mind that with a pressurized system you'll be chasing problems for a while until most of it has been replaced.

The motor runs great now, i have over 250,000km on my 318 with no plans to replace it soon. It's a great car but does need time and bit of money as ceeker said.
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Old 12-23-2010, 08:27 AM   #6
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I've had my 318 for about 5 years and the only overheating issue was when one of the small coolant hoses under the throttle body tucked in the upper manifold burst. a couple months ago i replaced all the hoses and did the replacing with only 3 hoses

i'm at i've done about 5000km since then, i'm at 328000 overall and now my temperature usually sits at about 1/4
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Old 12-23-2010, 08:59 AM   #7
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200000km is breakin point for these motors. I have 500000km plus on mine when the car was retired, and alot of those were hard KM's. A
loose fan belt can even cause temp issues. Heating issues are an easy fix on e30s. If the rest of the car is in good shape go for it
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Old 12-23-2010, 10:19 AM   #8
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I wonder if its really even over heating, or if its the wonderful e30 temp gauge that loves to dance around. Likely a loss of pressure from an external leak would be the culprit of a real overheating issue. Bleeding water pump is likely. Even a small leak from under the intake manifold or one of the throttle body heater plate hoses wouldn't surprise me. when you say it has 220000miles I assume you mean kms. I wouldn't worry about that. Between my dad and I, we have three 318i/is's all with 290+ kms (my coupe has 317,000kms and it runs fine even after beating the crap out of it all summer. I wouldn't be affraid of a minor overheating issue unless it is the head gasket, but you'd be able to tell that by looking at the oil, plugs, coolant.

Originally Posted by richie_s999 View Post
Grow up and move on.
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Old 12-23-2010, 10:45 AM   #9
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My last E30's temp gauge used to drive me nuts thinking that the car was overheating.

I am not sure about the mileage because I cant get in touch with the seller. The car is listed as '200k'. The car is from the U.S. so I assume he means 200,000 miles but it could be kilometers.

It doesn't matter anyways since the seller is not responding... The search continues!
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Old 12-23-2010, 12:06 PM   #10
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changing a fan clutch, a thermostat and new coolant shouldnt be much. If the car is clean get it. E30 318is are great cars.i would also change the tensioner and you ll have plenty of miles full of fun!!!!

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Lo there do I see my brothers and my sisters.
Lo there do I see the line of my people back to the beginning.
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