M42 Overheating

[Aufbau Principle]

Temp gauge went into the red on the way home, stopped to let it cool down a bit, kept driving. Blew the upper heater hose that goes from the firewall to the engine block.

Replaced that, but the car still overheats within about 15 minutes of idling, less when driving it slowly around the block.

There's no heat out of the vents with the heat knob turned all the way up. Fan doesn't seem to blow either when turned all the way up, all vents open, all sliders to the right.

Upper and lower radiator hoses don't feel like there's any pressure in them. Doesn't seem to be leaking anywhere else.

Checked the oil cap and dipstick for milkshake, oil's dirty but otherwise fine. No white smoke out the exhaust.

Car starts up, idles, and drives just fine, I shut it off when the temp gauge climbs past the 3/4 mark.

What are the possible culprits? Busted water pump, busted thermostat, clogged hose somewhere, clogged heater core/valve/radiator? Shitty bleed job?

EDIT: Just checked the car again, now pissing coolant somewhere around the lower radiator hose, just behind the expansion tank.

[roguetoaster]

As in the hose actually ripped open or flew off? To me that would be indicative of combustion gasses in the coolant. But let's not jump to a head/gasket failure since there are no overt signs of it.

Did you bleed the system correctly and thoroughly after replacing the hose? You can read through all of the various methodologies if you want, but it's not complex. Try it again, if no positive result you might have a clog in the system, probably in the radiator. You might want to check tension on your alternator belt (which drives the fan and pump IIRC), and correct operation of your clutched fan.

A leak showing at the lower part of the expansion tank is generally one of the two expansion tank seals.

[Aufbau Principle]

Did the "newspaper test" on the clutch fan while the car was warm, one rolled up sheet slowly brought into it from the side does not stop it.

The hose had a rip in it just above the nippleish thing that it attaches onto at the engine block

Picture:

E302 (1 of 3) by AP Photomatic, on Flickr

Just realized I was a dumbass and didn't actually add any coolant to the car once I had it jacked up and running with the screw open. Oop.

Both upper radiator hoses going into the thermostat housing have no pressure to them whatsoever even with the car warm. Pulled the one on the drivers side after it was warm and started the car, no fluid came out. I'm thinking stuck thermostat. Gonna pull it tomorrow and check.

[bmwman91]

Sounds like a busted water pump impeller to me. The hose on the driver's side is the high pressure side (pump outlet) IIRC, so you should have had at least some coolant coming out. Some OE-replacement water pumps have plastic impellers, and those do seem to have a habit of exploding. Maybe you had one of those in there? Anyway, hopefully it is just the thermostat somehow. It's a bitch to get all the plastic bits out so they don't clog up any passages in the head or radiator...LOTS of backflushing with a hose lol.

[Aufbau Principle]

What if there's no pressure in the pass. side hose either?

[bmwman91]

At idle there probably won't be much pressure. Rev it to ~3000RPM and that should make a mess with a hose disconnected. If still no pressure anywhere, then I would bet on the pump being dead.

[Aufbau Principle]

Updates.

Checked the thermostat and water pump. Thermostat was the wrong temperature so I replaced that, water pump was fine. I flushed the radiator with a hose. Upper radiator hose gets hot now. Still overheats. Is the only thing left a clog somewhere in the engine?

[bmwman91]

If you disconnect the 2 main radiator hoses and try running a hose through the top inlet, does water come out the bottom? Maybe the radiator is plugged?

[Aufbau Principle]

Yup, did that. Water comes out of the radiator fine. Is it fine to run a hose through the thermostat housing and out the other end to try blowing stuff out of the engine coolant passages?

[bmwman91]

Yeah might as well give that a shot.

[Aufbau Principle]

Putting in my nomination for Worst Mechanic 2014, I managed to crack both of my thermostat housings today trying to put the car together...

Really don't feel like the car's worth buying another housing for, gonna try JB welding it tomorrow.

[bmwman91]

Done that myself once by fully tightening each bolt all in one go. The first one crushed the gasket, and when I put the opposing one in, it levered the tab under the first one and cracked the housing. Since then I have always been careful to put all bolts in finger tight at first (with everything, not just the tstat housing). How did you do it?

[Aufbau Principle]

Same thing you did. Do you actually bother torquing it to the ~7.5 ft*lb the Bentley calls for?

[bmwman91]

Nah, I have never really observed the torque specs for stuff like covers and manifolds, although I will say that everyone else should do so and not follow my sloppy example! I typically go by the "feels tight enough" method, which is generally OK for non-critical stuff. Head bolts and critical bits like that are where I definitely DO follow the recommended guidance.

[Aufbau Principle]

Mmmk, will try good'n'tight over my $20 torque wrench from Harbor Freight next chance I get a crack at it. JB Weld didn't stop the leak when I put the housing back on today, being more careful with tightening the bolts evenly. Can't hurt to give it another shot but looks like I might have to get another housing.