I resently bought a 1988 325is from a car dealership. The dealer told me the car had a blown head gasket causing it to overheat. The car does overheat but there are no signs of a blown head gasket, no smoke in the exhaust, no oil mixing with antifreeze, no oil or water around the head gasket. I thought these were all the signs of a blown gasket, which this car has none! The dealer's mechanic told me he removed the thermostat and the car still overheated. After getting it home(towed), I stuck the garden hose down the coolant expansion tank and ran the car, still overheated! Next I opened the bleed air screw on the thermo housing and opened the radiator drain, ran the car with the garden hose in the exp. tank and the car ran cool!?! But at no point did I get straight liquid out of the bleed air screw, just steam and a few bubbles. I left it running and closed the drain and bleed air screw and the car slowly overheated again! I plan on reinstalling the thermostat ASAP and testing that, but no clue what to try after that possibly fails??? Please if you've got any info regarding the above problem let me know, your suggestions or solutions are greatly appreciated.
Overheating Issues
- Thread starter jstrausl
- Start date
Could it be your water pump? How about your fan clutch? Both have the possibility of letting your engine overheat. Try this - at the top of the radiator on the driver's side are two switches. These are high temp switches and will close when the radiator gets too hot (supposedly). One switch makes the aux fan run at low speed and one switch makes it run at high. Pull the contacts off one of the switches and short the wires together. Use a paper clip or something. The fan in front of the radiator should turn on. If your engine stays cool with this auxilliary fan running then your fan clutch is bad. I have this problem right now. If it still overheats your water pump might be bad or you may have some blockage in your cooling system somewhere. Don't know why your bleed valve never ran clear.
If you plan on keeping this car get a Bentley manual for it from Amazon (less than $40 - and a great investment). Also look to see when the timing belt was last changed. There may be a sticker on the Air Flow Meter or on your Fuse Box or on the tire fender in the engine compartment - somewhere it might say at what mileage the timing belt was last changed. If it was more than 50,000 miles ago that should be a priority for you. If you can't find it and the car has more than 60k miles change it immediately. If the timing belt breaks you won't wonder about the head gasket anymore because you'll be changing it soon.
Good luck and keep us posted.
Steve
If you plan on keeping this car get a Bentley manual for it from Amazon (less than $40 - and a great investment). Also look to see when the timing belt was last changed. There may be a sticker on the Air Flow Meter or on your Fuse Box or on the tire fender in the engine compartment - somewhere it might say at what mileage the timing belt was last changed. If it was more than 50,000 miles ago that should be a priority for you. If you can't find it and the car has more than 60k miles change it immediately. If the timing belt breaks you won't wonder about the head gasket anymore because you'll be changing it soon.
Good luck and keep us posted.
Steve
Also do this -- its not the smartest thing but it works and shouldnt damage a thing.
Turn the car on, and stick a rolled up piece of newspaper (so its thin enough to bend easily) and put it into the fan. If the fan slows down or stops, your fan clutch is bad. It's not a very difficult repair either.
Turn the car on, and stick a rolled up piece of newspaper (so its thin enough to bend easily) and put it into the fan. If the fan slows down or stops, your fan clutch is bad. It's not a very difficult repair either.
If your expansion tank is bubbling, I would say it has a blown head gasket. Exhaust is probably leaking right into your coolant.
Conditions of a blown head gasket depend on where the gasket is blown.
Exhaust to coolant,
Coolant to oil,
oil to exhaust, etc.
There's a certain test to see if it is a exhaust to coolant problem. I forget what it is exactly..... Let the car cool off completely. Start it with your expansion tank cap off, and if it boils quickly... head gasket.
Something i found for signs to tell if blown head gasket: "white smoke of your tail pipe, or loosing coolant through your overflow , take the cap off and rev the engine, if you see bubles or if it comes out you ll know"
Conditions of a blown head gasket depend on where the gasket is blown.
Exhaust to coolant,
Coolant to oil,
oil to exhaust, etc.
There's a certain test to see if it is a exhaust to coolant problem. I forget what it is exactly..... Let the car cool off completely. Start it with your expansion tank cap off, and if it boils quickly... head gasket.
Something i found for signs to tell if blown head gasket: "white smoke of your tail pipe, or loosing coolant through your overflow , take the cap off and rev the engine, if you see bubles or if it comes out you ll know"
Here is the procedure that I'd highly recommend...
Priority 1: Mileage since last timing belt/water pump change. If it's more than 50K miles (as Steve has already mentioned![[:p]](/images/smilies/tongue.png "Stick Out Tongue [:p]")
, you need to change the following items:
Priority 2:
If the timing belt is okay, also the water pump, I'd start with replacing the thermostat with the 71 degree C one as opposed to the 75 or 80 degree one...trust me it will help. Drain the coolant, pull the radiator and flush it completely. If the water pump, thermostat and fan clutch are okay...a clogged radiator will still cause it to overheat.
I would recommend the new coolant mixture to be one bottle of Redline Water Wetter and the rest water. If you're in a warm climate I wouldn't worry about antifreeze.
Priority 3:
The best test of whether or not the fan clutch is bad is to use a timing light...not a stick or putting anything else into the fans path. If it's the original 15+yr old fan (and it probably is) the very LAST thing you need happening is for a piece to break of at any engine speed. Just picture a small plastic missile being shot into your neck or face because you stuck something in there.
If the car runs at normal temperature while moving down the highway and slightly higher while driving on city streets, but starts to overheat in stop-n-go traffic or while sitting at the light...it's about a 95% chance it's your fan clutch.
Here's the theory...if the car is cool and maintaining temperature at freeway speeds, the radiator is working because air is flowing over the surface and cooling the coolant. How efficiently depends on how clean the inside is and how many bent fins you have.
If the car starts to overheat while stopping or moving in stop-n-go, this is where your fan clutches job of locking the thermal/viscous clutch and spinning pulls air through the radiator.
Priority 1: Mileage since last timing belt/water pump change. If it's more than 50K miles (as Steve has already mentioned
, you need to change the following items:- Timing Belt
- Timing Belt Tensioner
- Water Pump - while not required, it's highly recommended. This $45 part will kill your car somewhere down the road and leave you completely stranded. $45 is CHEAP insurance for 50K miles.
- Gasket for water pump
- Thermostat - only cost a couple of bucks
Priority 2:
If the timing belt is okay, also the water pump, I'd start with replacing the thermostat with the 71 degree C one as opposed to the 75 or 80 degree one...trust me it will help. Drain the coolant, pull the radiator and flush it completely. If the water pump, thermostat and fan clutch are okay...a clogged radiator will still cause it to overheat.
I would recommend the new coolant mixture to be one bottle of Redline Water Wetter and the rest water. If you're in a warm climate I wouldn't worry about antifreeze.
Priority 3:
The best test of whether or not the fan clutch is bad is to use a timing light...not a stick or putting anything else into the fans path. If it's the original 15+yr old fan (and it probably is) the very LAST thing you need happening is for a piece to break of at any engine speed. Just picture a small plastic missile being shot into your neck or face because you stuck something in there.
If the car runs at normal temperature while moving down the highway and slightly higher while driving on city streets, but starts to overheat in stop-n-go traffic or while sitting at the light...it's about a 95% chance it's your fan clutch.
Here's the theory...if the car is cool and maintaining temperature at freeway speeds, the radiator is working because air is flowing over the surface and cooling the coolant. How efficiently depends on how clean the inside is and how many bent fins you have.
If the car starts to overheat while stopping or moving in stop-n-go, this is where your fan clutches job of locking the thermal/viscous clutch and spinning pulls air through the radiator.