Overheating

[JGood]

Car is an 85 325e, cammed m50b25tu, m42 rad, thermostat controlled electric pusher fan. Newer fluid, verified the fan is kicking in and working fine.

If the car idles for more then 5 minutes with temps in the 80's or more, it overheats, even with the fan running. When I start driving the temp drops right away back down to normal levels.

It never did this before in ~3 years and ~40k miles, and I haven't changed anything.

Haven't touched the coolant level in months, so it's not leaking.

I never messed with the thermostat or water pump, but I'd think those would cause major issues if they failed... not just this idle overheating issue?

[7pilot]

Did you renew the water pump when the engine was swapped into the E30?
Without trying to teach you to suck eggs there are 3 water pumps with different impellers.
1, the bad plastic impeller version.
2, the metal impeller version.
3, the composite impeller version.

It is possible that the thermostat is sticking in the partially open position.

I'd recommend a water pump and thermostat change.
I'd also throw in some Water Wetter to prevent "microboiling" in the head.


m

[blackhawkimpact]

Mines does the same thing. But it doesn't actually overheat just the gauge rises on idle even if the both fans are on

[Jand3rson]

Did you renew the water pump when the engine was swapped into the E30?
Without trying to teach you to suck eggs there are 3 water pumps with different impellers.
1, the bad plastic impeller version.
2, the metal impeller version.
3, the composite impeller version.

I suspect your water pump. When I had my M50 apart before I put it in, before just ordering a new one willy-nilly, I checked mine. It's the metal impeller version, which means it was replaced at some point, and there was no shaft play or anything, still spun very freely, so I just went ahead and kept it as-is. I'm using the M42 radiator and thermostat-controlled electric fan, too.

[JGood]

Thanks guys. I didn't replace the pump or the thermostat when I put the engine in, and it's a high mileage engine, so I'll just order both.

7pilot, do you recommend the composite or metal pump?

I have some water wetter left over from my track car, not sure why I didn't think to throw it in this car. Will do.

[giantkeeper]

Thanks guys. I didn't replace the pump or the thermostat when I put the engine in, and it's a high mileage engine, so I'll just order both.

7pilot, do you recommend the composite or metal pump?

I have some water wetter left over from my track car, not sure why I didn't think to throw it in this car. Will do.

I know you did not ask me, but I went with Stewart and never looked back. Do it!

[JGood]

I know you did not ask me, but I went with Stewart and never looked back. Do it!

The engine has 260k miles, and the car is rotting to pieces, I'll be happy if it makes it another year. No way I'm putting a $200 pump in! Just doing little things to keep it running reliably until the chassis breaks in half or I launch piston chunks out the exhaust.

[luckysnafu]

Sounds like the system wasn't bled properly. I had the same problem with my m52 and m42 radiator until I drilled a hole in the top of the thermostat and rebled the system. Now I don't have problems overheating with just a 14" pusher fan.

[JGood]

Sounds like the system wasn't bled properly. I had the same problem with my m52 and m42 radiator until I drilled a hole in the top of the thermostat and rebled the system. Now I don't have problems overheating with just a 14" pusher fan.

Well, it was bled 3 years/40k miles ago, hasn't been touched since, the coolant level hasn't changed, and the problem only started recently...

[jrdeamicis]

Water pumps are just mechanical things. Either they are spinning or not. So just pull it out and make sure the bearing is good.

If it were my car I would do a new thermo and a composite pump if you have the metal style.

You could also get a coolant system pressure gauge and see if cylinder pressure is leaking into your coolant system. It doesn't have to much to make things annoying in there.

[JGood]

Water pumps are just mechanical things. Either they are spinning or not. So just pull it out and make sure the bearing is good.

Can't the shaft break, leaving the pulley spinning, but coolant not flowing?

If it were my car I would do a new thermo and a composite pump if you have the metal style.

Is there any reason behind getting a composite pump? Not that I don't trust you, I just want to know why I'm buying one or the other.

Thanks

[giantkeeper]

the chassis breaks in half or I launch piston chunks out the exhaust.

in for pictures :D

[JGood]

Well, disregard this thread. My electric fan fuse melted, so the fan wasn't coming on. Which blows my mind, because the first day it overheated on me, I got out, looked through the grill, and saw/heard the electric fan spinning (it's loud). Maybe it was intermittent at that time.

Anyway, spliced a new fuse in, let the car idle for 10 minutes in 95 degree heat, and it didn't even touch the half way line, so I'm good to go.

Thanks anyway, everyone!

[JGood]

in for pictures :D

I can show you pics the cracked shock towers, cracked trunklid/quarter panel area, rusting firewall, etc... if you'd really like. haha

I just don't have it in me to let the car go yet. It was my first car, I've had it 11 years, put on 200k of the 300k miles that are on it, myself. I'm way beyond emotionally attached.

[328ijunkie]

M42 rad is your problem


:D