Another M42 overheating problem

[bleedblue]

Car has about 220,000 miles on it, I purchased it about 4 months ago and put on about 500 miles. The gauge read 3/4 about 2 weeks ago and found the tstat faulty and a/c fan resistor faulty. It ran fine for about a week and now back to the 3/4 mark. I work at the local bmw dealership which is a plus and had one cert tech do the repairs.

It could possibly be the tech didn't bled the system well enough or could be another component. I'll have him remove the cluster and check the ground nut as well. Driving today I did notice the temp gauge needle jump side to side quickly as I was about to die out. That was new to me. I'm sure the tech will look it through again, but any ideas where I should look? read the temp off the radiator? Check the water pump? Check the tstat again? Check for proper bleeding?

[jdt10768]

bad connection at brass ground nut on back of cluster for temp gague

clean that contact point and retighten

[bleedblue]

^^ thanks will def do that and update

[oldmann]

Read temp at thermostat housing with a Non-contact thermometer of some kind. Usually accurate to within a few degrees, without having to open up the system.

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[bleedblue]

thanks for the info, I'll try that as well

[bleedblue]

Update - as the temp gauge read in between the half and 3/4 mark, used an infared temp gun and pulled 117-124 degrees right in the center. Top and bottom in the 160-177 degree range. Most likely clogged radiator. I'm not ruling out the ground nut and as I'm checking that currently.

If the radiator is the issue. Thinking about upgrading to a Mishimoto one.

[bleedblue]

So instead of buying a new radiator we performed a reverse flush on the radiator. Did it twice and now it reads properly in all areas. It did climb pass the 1/2 mark and tapped on the cluster only to bring it back to half. Def connection on the cluster as well.

[roguetoaster]

Assume you are now happy with the stock radiator:

I don't think that Mishimoto is really an upgrade. I say this as an M42 with an otherwise healthy stock cooling system will function fine (even in stop and go traffic) with a barely operative clutch fan. Further, on the endurance race car we omitted a fan by choice and have had no issues at all.

Basically, the stock cooling system is more than sufficient for the needs of a standard M42, and "upgrades" to this system seem to be more often done for cost considerations/cosmetic reason rather than actual need. Yes, I understand that you can remove the clutched fan to save .1HP, but why?

[oldmann]

Have you ever removed the aux. fan? Almost all will have what resembles a birds nest crammed in behind the fan clogging the air flow. Take a look.

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[bleedblue]

Yes I'm sticking with my stock radiator, a co worker did talk to me about not buying the mishimoto. I'll follow yours and his advice.

Assume you are now happy with the stock radiator:

I don't think that Mishimoto is really an upgrade. I say this as an M42 with an otherwise healthy stock cooling system will function fine (even in stop and go traffic) with a barely operative clutch fan. Further, on the endurance race car we omitted a fan by choice and have had no issues at all.

Basically, the stock cooling system is more than sufficient for the needs of a standard M42, and "upgrades" to this system seem to be more often done for cost considerations/cosmetic reason rather than actual need. Yes, I understand that you can remove the clutched fan to save .1HP, but why?

[bleedblue]

I haven't, but did find 2 paper napkins hanging around that we removed. The car has been running fine.

Have you ever removed the aux. fan? Almost all will have what resembles a birds nest crammed in behind the fan clogging the air flow. Take a look.

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