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engine overheating

20K views 12 replies 9 participants last post by  Jarrod90 
#1 ·
1996 BMW 318i. Have changed thermostat, water pump. Engine seems to have air still in system even after multiple bleeds. Any help would be appreciated.
 
#4 ·
remove thermostat and run engine. with an open radiator cap u should be able to see the flow of the coolant... no flow or weak churn in the filler hole = radiator is clogged(fully or partially).

If it's flowing nicely... check compression. u may have a head problem.

*Check also for coolant in oil... or traces of oil in ur antifreeze/coolant. Blown head gaskets definitely will make an engine overheat
 
#5 ·
Original problem that started all this was the plastic water jacket on back of head blew out. After changing this part the other plastic water jacket below intake blew out. Changed this part and noticed little to no movement of coolant, removed t-stat to eliminate and still had problem. Decided to change water pump because of little to no water movement. No oil in coolant, no coolant in oil, and not appearing as white smoke in exhaust. But after about 10 minutes idling the temp starts to rise and have to shut off.
 
#6 ·
clogged radiator?

*but eeek...! sounds to me like your cooling system is pressurizing fr somewhere. I hate to say it but u may have a blown gasket(i.e. compression from cylinders leaking into your cooling sys.)

easiest way to tell... pull out thermostat. fill your radiator with water, and with radiator/reservoir cap open. Start engine.... if the water blows out of ur radiator/reservoir, it's definitely a blown head.
 
#9 ·
i had this problem on my 318 changed everything in the hope the head was fine but it finally went when i changed the starter motor. anyway tested starter and it blew the gasket right out if the back of the engine still better there than tanking down the road

the water only go's round the head while its cool then go's round the rest when its warmed up
 
#10 ·
I would try this before jumping to conclusions! I had the same problem when I replaced my waterpump & thermostat! 1st make sure the thermostat is in the right position arrow or dot up^. Then try this.........
goodluck,
johnny,

u n d e r s t e e r . c o m

10) It really helps to have a friend lend a hand by sitting in the car revving the motor and keeping an eye on the temp gauge. Start off by removing the coolant reservoir cap and the plastic bleeder screw right next to it. Fill the coolant reservoir with a 50/50 mix of coolant and distilled water. Have your friend start the car, turn on the heater to full hot on the vent position and rev the motor to about 2500 RPM, if the temp gauge goes past the 12 o'clock position, shut the motor off, let it cool down and start over again. Watch the coolant reservoir, as the engine warms up the coolant level should drop, refill as the coolant is sucked out of the reservoir. Watch the bleeder screw hole also, when coolant with no air bubbles begins to overflow then you're almost done. It's a good idea to have some paper towels handy to mop up any overflow. Screw the bleeder screw back in (be careful to not break the plastic screw) and continue to rev the motor, you should see a continuous stream of coolant spraying in to the reservoir from the small hole at the top. Continue letting that spray in to the reservoir while your friend revs the motor for a couple of minutes, until the gauge hits the 12 o'clock mark, to ensure any remaining air is gone. If the heater is blowing hot air when you're revving the motor AND when the engine is at idle then your cooling system is properly bled. If your vents are blowing cool air at idle then you still have air in the system, try revving the motor more and/or squeeze the radiator hoses to help dislodge any trapped air. Once your system is fully bled, top off the reservoir and replace the cap. Check the coolant level in a day or two and top off as needed.
 
#11 ·
Gday would appreciate anyone's help having a similar overheating problem with 1994 318i m43 engine, Car holds normal operating temp consistenly with days where tempuratures are below 32'celcius but on hot days 32'c and upwards i experience a very slow overheating problem where temp gauge will slowly creep above normal operating after about 10 minutes of driving. When pulling over and idling temp comes down very slowing after 10 minutes or so usually. Mostly wondering if this could be normal and is only due to extreme temps we get here in days of summer in australia (today reached top of 42'c)? Have checked Auxilary Cooling Fan, and viscous belt driven fan appears to operate ok. Would appreciate and ideas?

Also in regards to other blokes problem if have trouble bleeding the cooling system try loosening the intake manifold cooling hose at the pcv valve for few seconds letting some coolant bleed out there at operating temp.
 
#12 ·
I had 318i M43.
Paid to have head gasket done.
600 later, continued to do it.
If the thermostat gets stuck open or shut it will send the temp gauge straight up.
This obviously is an un true reading as it is stuck.
Is thermostat opening/shutting properly?
Does the water disapeer? If so Where?
Mine didnt show any signs other than the gauge going to red.
No white smoke.
It kept drinking water though, everyday.
It finally gave up on me.
When i did open it back up, the head had been corroding, due to a crack in the side which had allowed water to seep in, very slowly, but thus killing my head. The result was, it slipped a valve, smashed a piston, and now i have a new car.
Reakon its the head gasket mate!
 
#13 ·
Cheers for reply bud
Just replaced old viscous coupling turns out was buggered i'd neglected to check it.
Runs slightly cooler now too, A/C works slightly better too added plus with the extra air flow. Have to wait and see what she like on hotter days
Never had temp gauge go straight up just gradual up to about 3 quater over 4-5 minutes and only on those really hot days
Yeh ive heard a lot about head gaskets bein no good on em but i fail too see any signs of a failing head gasket, No sweet smell or white smoke from exhaust, Loosing slightest bit of coolant 50 - 100ml every 2 -3 weeks max appears to be coming from bottom raditor hose (just starting to see slight coolant stains on raditor) haven't replaced as yet.
She has done 236,000kms guess, ill have to pull out the compression tester and see if any major variences between cylinders and hope for best. Any idea what compression specs are roughly (kpa/bar)?
So no signs of head gasket goin? what about rough cold starts when coolant left in cylinder bores after leakin all night?
thanks again bud
 
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