e46 Slow Overheat - Headgasket? New WP, ET, Hoses, Fan

[FerThewin]

Hello!




I've just bought my first bmw, 2001 330i with 150k miles, Automatic. Pristine condition, except I bought it overheating for $500. Before I bought it the guy has been trying to fix it for 6 months, throwing parts at it. He wasn't able to fix the overheating, which was why I got it for cheap. Previous owner replaced T-stat, radiator hoses, ET, waterpump (The one with metal impellers).


Main Question: Could a blown headgasket, or warped head cause me to overheat slowly like this? (No milky coolant, No coolant in oil). I'm prepared to DIY replace the headgasket, but I want to be sure my dumbass didn't miss something in the coolant system first.


I replaced the Fan clutch (Fan was previously very easy to stop and blew very little air). After replacing fan clutch, it feels like its blowing air much better... Took it for a test drive, But its still overheating.




About the Overheating, its a very slow overheat. If a idle, it take about 20-30 mins sitting in my driveway to hit 200 degrees F, Overheating starts at about 238 degrees F. If I'm driving around, its probably 2-3 miles or 10mins of driving before overheating starts.




Also I think the coolant level sensor is leaking slightly at the bottom(Can this affect it?) of the ET. Secondly, The previous owner when he changed the ET, he kept the old cap, bc he said the new one didn't screw on tight. The old cap locks tight, because it makes a vacuum sound when I open the ET cap sometimes(So I guess its good).
Side note: When I first bled the system, I filled up the ET to top (With no air room) because I was a noob, and ran the car till it started overheating. Dunno if this would mess up anything.


Also when it overheats, the lower radiator hose feels warm, not boiling hot (is that normal?)


so based on all this... Could a blown headgasket, or warped head cause me to overheat slowly like this? (No milky coolant, No coolant in oil). I'm prepared to DIY replace the headgasket, but I want to be sure my dumbass didn't miss something in the coolant system first.




I am pretty mechanically inclined, and have been working on cars as a hobby for several years.


Also.
With Heater On - Engine Cold - A/c Blows room temp air
With Heater on - Engine Hot - a/c blows hot air




Yes, I have bled the cooling system (4 times to be exact) numerous different ways. All on an heavily inclined driveway.


(Did this 3 times, never saw any air bubbles come out, only more coolant from bleed hole) (I also squeezed upper radiator hose once to see if there was an air pocket to burp, nope)
Bleeding procedures I have tried.
Remove the coolant filler cap
Turn the ignition on but do not start the engine
Turn the climate control to the highest temperature and put the fan on the lowest setting
Slowly pour coolant into the expansion tank until coolant runs out of the bleed screw hole
keep pouring coolant until you no longer see any air bubbles in the coolant coming out of the bleed screw hole
Replace the bleed screw and check the coolant level in the expansion tank
Replace the expansion tank cap and start the motor
Allow the car to idle until normal operating temperature is reached
Watch carefully to make sure the temperature gauge doesn't rise above 12:00
If the gauge starts to move past 12:00 shut the car off immediately, let it cool and start over




(Did this once)
Set ignition to position 2 and adjust heater so the max heat is on and the fan is on lowest setting. Leave ET cap OFF. Start car. The minute you start the car the water pump basically scoops all the coolant and starts to push it through the system. With only half the coolant in the system it will get hot fast and thermostat will open. The waterpump doesn't push air so you have to start adding the rest of the coolant.


Continue to add coolant slowly - at this point you need to rev the engine about 4 times up to about 4000 RPMs so that the waterpump is spinning hard enough to push the water through the coolant system. As the system fills it will push water easier and you will see the coolant starting to cycle as it will begin spitting back into the ET tank at the bottle neck. At this point you'll have about 90% full. Since the coolant is now getting hot put the cap on the ET tank.


Rev the car once or twice more and then open up the bleeder screw at the ET tank - don't remove it just turn it back a couple of turns to let the remaining air escape. This takes about 2 mins.


Turn car off - let it cool then adjust the ET tank level to the recommended bobbing position for a cold tank. Might take another 1/2 liter at most.

[MIKYZZ4]

Perform a leakdown test on all cylinders,
this should confirm a blown headgasket.

[FerThewin]

Okay I'll do that

So I also just re-bled again, and did a test on a cold night.

The upper Radiator Hose is boiling, but Lower radiator hose is ice cold.

T-Stat problem? Possibly previous owner messed up T-stat replacement?

[TonyAngel]

When thermostats fail, they usually fail in the open position, although I've read of a few sticking closed. If one hose is getting HOT and the other only gets warm, I'd first suspect a circulation problem. I wouldn't immediately jump to the conclusion of a bad head gasket.

It is common practice among those here to do a complete cooling system refresh at about 100k miles, if not sooner. Mostly due to cracking plastic, but I've seen clogged radiators on cars with far fewer miles too. I suppose you could pull the radiator, feed water into the inlet and see if it flows freely from the outlet.

Really, when the PO started throwing parts at the car, he should have done a refresh and it appears that he replaced most parts but neglected the radiator. I'd also check the hoses and pulleys. I've never seen it on BMWs (I'm new to those), but I've seen very old and worn hoses collapse and restrict water flow too. I've also seen transmission going bad causing the engine to overheat.

In short, based on what I'm getting out of your post I think you have a circulation problem and I suspect the radiator.

[MN2K740i]

Hate to say it....but it seriously sounds like you have either air, or a stuck T-Stat that's stuck shut. My 5 did the stuck T-stat thing to me last winter....except driving I would hit max temp in under a mile.

Do we know for fact that the belts are properly routed as well? I don't think you can put them on the wrong way and have the car still be operational.....but all the same....there's not much that really surprises me anymore lol.

[TonyAngel]

A thermostat stuck closed would certainly present a circulation problem, but I think the OP said it was changed. If I remember right, getting the thermostat installed wrong would be a hard thing to do.

[MN2K740i]

I've seen tstats bad out of the box before in my parts store days....kinda like spark plugs, you only have to drop them just right once before they're broken lol.

I hate cooling systems in general, but these cars aren't too bad to deal with....I just wish the pressurised systems never came up....so much easier in the old days ​lol

[vegaslightsss]

Do what the first response said and perform a cylinder leak down test. Any loss over 5% is considered excessive. Pull all your plugs and do it on each cylinder. What ever cylinder you are testing need to be TDC of the compression stroke so the valves are closed. Alternatively you can perform a block test which plugs the expansion tank and test the cooling system for exhaust gasses. If exhaust is pressurizing the cooling system it will not be able to circulate

[FerThewin]

UPDATE: Car is fixed! Thank you guys.


So it was a problem with the coolant flow. I was pulling off the hoses to check the condition of the radiator, and I noticed a huge chunk of what looked like a salt rock half the size of a tennis ball lodged in the radiator hose and thermostat. I'm guessing that the previous owner put stopleak in and told me that he didn't. After I removed the salt rock and put it all back together, the car runs like a dream now! No more overheating!


I think what happened was that the owner changed all the parts except for the fan clutch, then when the car was still overheating he thought it was a leaking coolant issue and put stopleak in. By the way, it looks like theres a huge salt rock in my expansion tank... I'm guessing some kind of stopleak.....

[MIKYZZ4]

I would remove the entire cooling system,
Flush all parts out with water to get most of the stopleak out.
Flush out the radiator from inlet and outlet,
Same with heater core inlet and outlet hoses.
Flush the engine block out as best you can with water hose.