If you are not farmiliar with my previous thread, it is here.
http://forums.bimmerforums.com/forum/showthread.php?t=744382&highlight=overheat


Story: Beginning of autocross season, my car would overheat only on autocross runs (during 2nd or 3rd runs). Never overheated on street. Radiator, wp, thermostat, housing, hoses are all almost new (less than 1 year). I took everything apart twice flushed everything with water, etc. Put it back togather, and both times it still overheated. Coolant would never squirt out though.

Decided to do head gasket. The gasket looked good, but the head was warped. Had the head pressure tested and decked. Put it back togather with new gaskets and new steward water pump.

This weekend, brought the car to the autocross, and it overheated on the 2nd run. Bled the cooling system during lunch, and a few bubbles came out. Ran the car again in the afternoon, and overheated on the 2nd run. GRRRR.

When i say overheated, i mean the temp started to move from the center of the stock gauge, then i would slow down or shut the car down. The temp never made it past the 2nd tick mark.

Options: I love the car. It has tons of maintenance and work done by me. I hate to get rid of it.

1. Sell car to someone who doesnt drive on track, runs perfectly. Take money and buy a different car, or another M3. Im not that shady, so this isnt really an option.

2. Buy used engine, and swap?

3. What would you do??

I am aganizing over this, and really need advice. I just bought a house and am very short on cash. What should i do?

Thanks in advance.

What temp thermostat and are you running any fans (engine or aux)?

The thremostat could also be bad.

First, I would get some type of data logger and see what the temperatures are really doing. The stock gauge is an idiot light really.

Second, I assume that the head was magnafluxed or dye dipped to check for cracks? If not, then that could be the issue. evosport chased a problem on their lightweight E36 M3 for more than a year and a half that they finally traced to a cracked head that would cause overheating only when driven on the track.

Thermostat is the low temp one from the fan delete kit, cant remember the temp. It looks to be in good condition, but i havnt replaced it for about 1.5 years. Replaced that over the winter 1 year before the problem started. I plan on pulling it and seeing how far it opens in water on the stove.

I am running a spal puller 16" replacing the motor fan using the factory low temp switch. Also, i replaced the failed acc. fan with another spal (pusher) which runs off the high temp switch. Both fans operate normally. After the first autocross run, both fans are on, which means the radiator temperature is at the high value (i cant remember the number). This also should mean that the coolant is flowing to the radiator adequatly..... right?

First, I would get some type of data logger and see what the temperatures are really doing. The stock gauge is an idiot light really.

Second, I assume that the head was magnafluxed or dye dipped to check for cracks? If not, then that could be the issue. evosport chased a problem on their lightweight E36 M3 for more than a year and a half that they finally traced to a cracked head that would cause overheating only when driven on the track.

The head was pressure tested. The machine shop said this finds cracks, and came up negative. It was not magnafluxed. Not sure about the dye dip....

What is the easiest way to wire up a temp gauge. Im thinking of leaving it in the cabin loose for testing purposes (cheap, nothing fancy).

1 = No

2 = Too extreme

3 = read on

First, make sure the air has been completely bled from system. Each time I've done mine it's taken me several times before I got it all out.

Here's what I do. Get the engine up to operating temp. Jack the front of the car as high as I can get it. With heater on full hot, blowing strong and engine running, bleed the air using bleed screw. Close screw, rev to 2-3K for a minute and then re-bleed. I do this several times until I'm sure there's no more air coming out. Now let it cool completely and top off overflow tank.

When you installed the thermostat, did you make sure the little hole in the thermostat was at the top? It let's air move from the block into the radiator.

Do you have a fan? OEM w/ fan clutch? Is it good?

Have you done any mods to the undertray or radiator shroud that would cause a problem with the flow of air thru the radiator?

If this doesn't solve your problem, there are tests that can be done to determine if you have bigger problems. One is to test for hydrocarbons in the coolant. This could indicate a problem like a head gasket, cracked block or cracked head. See a competent mechanic.

Good luck - Jay

Are you sure the fans are blowing in the right direction. crossed wires will spin them the other direction.

I second getting a real water temp gauge.

1 = No

2 = Too extreme

3 = read on

First, make sure the air has been completely bled from system. Each time I've done mine it's taken me several times before I got it all out.

Here's what I do. Get the engine up to operating temp. Jack the front of the car as high as I can get it. With heater on full hot, blowing strong and engine running, bleed the air using bleed screw. Close screw, rev to 2-3K for a minute and then re-bleed. I do this several times until I'm sure there's no more air coming out. Now let it cool completely and top off overflow tank.

When you installed the thermostat, did you make sure the little hole in the thermostat was at the top? It let's air move from the block into the radiator.

Do you have a fan? OEM w/ fan clutch? Is it good?

Have you done any mods to the undertray or radiator shroud that would cause a problem with the flow of air thru the radiator?

If this doesn't solve your problem, there are tests that can be done to determine if you have bigger problems. One is to test for hydrocarbons in the coolant. This could indicate a problem like a head gasket, cracked block or cracked head. See a competent mechanic.

Good luck - Jay

When i first bled the coolant, after the headgasket job, i used this method with the car jacked up. I bled the car twice letting it cool in between.

Yes, the hole is correct.

I removed the front shroud (aux) because the spal fan wouldnt fit with it.

In the 3.5 years i have owned the car, it hasnt had an undertray, but hasnt overheated till this year.

I had some very odd overheating issues at the track earlier this year and air was the culprit one time and the other was a failed primary belt tensioner.

Does your main drive belt have tension on it? Mine was working but the tensioner was worn out enough for the belt to slip off the water pump under hard brake or other sudden RPM changes.

I reinstalled the belt after the headgasket. It seemed to be tight, like normal. I remember reading your thread, so i specifically looked for this.

It could be that autox speeds just aren't high enough to cool the radiator without a bit of help from the fan. The factory thermoswitches trip at 90 & 91C as I recall and thaht might be enough of a delay to allow a higher than normal temp. It would be easy enough to find out if that's what's happening by jumpering the fans on for the next autox. If the engine doesn't run hot then you need a lower temp thermoswitch to bring the fans on sooner or install a cockpit override switch.

It could be that autox speeds just aren't high enough to cool the radiator without a bit of help from the fan. The factory thermoswitches trip at 90 & 91C as I recall and thaht might be enough of a delay to allow a higher than normal temp. It would be easy enough to find out if that's what's happening by jumpering the fans on for the next autox. If the engine doesn't run hot then you need a lower temp thermoswitch to bring the fans on sooner or install a cockpit override switch.

The fans run off a lower temp fan switch (from the fan delete kit). I forget the temperatures, but i believe the low is 88C. I really doubt this is the problem, as i ran the car in a similar configuration all last year and the year before with no problems.

The only change since the problem is this: knowing that the aux fan didnt work, i removed it along with the front shoud and replaced with a spal fan. This was only precaucionarry as with the single fan, the car never overheated.

1) Did you use a stock head gasket? If so, did you retorque the head bolts after the first heat cycle?

2) Test the coolant for hydrocarbons. If this is negatives then at least you have eliminated further head leaks as a root cause.

1) Did you use a stock head gasket? If so, did you retorque the head bolts after the first heat cycle?

2) Test the coolant for hydrocarbons. If this is negatives then at least you have eliminated further head leaks as a root cause.

I used a stock HG. Nothing i read said to retorque after the first heat cycle (until now). I thought that was only for MLS gaskets. Also, the stock head bolts are torque to spec, then do (2) 90 degree turns.

I havnt done the hydrocarbon test, but have heard that it doesnt always work.

I haven't re-read your first post, but have you replaced the radiator?

If this problem has come on slowly after 3 years the radiator may have some rows clogged.

I also saw a tip about soaking the outside of the radiator with simple green, let is soak for a few hours and then flush it from the engine side. I may have read that in your first thread though.

Joe

I used a stock HG. Nothing i read said to retorque after the first heat cycle (until now). I thought that was only for MLS gaskets. Also, the stock head bolts are torque to spec, then do (2) 90 degree turns.

I havnt done the hydrocarbon test, but have heard that it doesnt always work.

Aftermarket stud kits (Raceware in my case) recommend a retorque after the first heat cycle. I have gotten movement on the nuts with a stock HG, but not with an MLS gasket. Not sure how you'd even check stock head bolts designed to stretch with the angle procedure (i.e. don't know what a good torque value would be).

I used a stock HG. Nothing i read said to retorque after the first heat cycle (until now). I thought that was only for MLS gaskets. Also, the stock head bolts are torque to spec, then do (2) 90 degree turns.

I havnt done the hydrocarbon test, but have heard that it doesnt always work.



You should not have to re-torque stock headbolts. They are torque to spec and should be tightened with a degree wheel.

Headstuds need to be re-torqued (or at least checked) after the first heat cycle regardless what gasket material you are using. I found a few of mine to a slightly loose after I ran my motor after the head was rebuilt.

Ok, so it sounds like i did the head gasket job correctly....

The radiator is about 1.5 years old. This did not come on slowly, it just started happening. I cant immagine the radiator being clogged. I flushed it out with water several times while i had it out. Its still shiny. It only has like 10k on it.

As you can tell, i am really bumming. Where do i go from here?

Ok, so it sounds like i did the head gasket job correctly....

The radiator is about 1.5 years old. This did not come on slowly, it just started happening. I cant immagine the radiator being clogged. I flushed it out with water several times while i had it out. Its still shiny. It only has like 10k on it.

As you can tell, i am really bumming. Where do i go from here?

Put it on a dyno at a good shop.

Heck, even an emissions dyno might tell you something, thats $30.00 here in Virginia.

Have you sent an oil sample to BlackStone?

Joe

Wow, this sounds exactly like my story. For what its worth, I am going to upgrade my radiator, and add a spal. I will let you know my results.

My educated guess is a cracked head. I took mine to two shops before they found the cracks. Replaced the casting and the issues were gone. Our heads are notorious for going.

My educated guess is a cracked head. I took mine to two shops before they found the cracks. Replaced the casting and the issues were gone. Our heads are notorious for going.

Wouldn't the pressure test point out any cracks in the casting? Or is the pressure testing not an accurate way to test the head?

I had a pressure test on my head but you can't simulate the pressure it gets in the real world especially tracking the car. Dye testing showed my cracks.

It won't solve the problem, but when AutoX'ing you may want to try running with your heater on full hot. I've noticed that some of the E46 M3 guys do this to help keep their water temps in check.

Huh. What did it cost for the testing? If i do this, it would mean another head gasket kit, another pack of bolts, plus the testing. Also, i would need to find a competent shop to do the testing. Then, if i find a crack, what do i do? Does that mean head replacement? If so, what is the best way to go about it?

Just trying to figure out my options, etc.

Thanks

If it is a head crack it will only leak when it is hot. It takes the heat to make the metal expand to the point that the crack opens up.

These cars need the shrouds around the radiator and the undertray to cool it like the factory intended. Removal of these shrouds will adversely effect it quite a bit more than you would think. I would try removing the puller fan and putting the factory inside shroud back on and go thrash it in a parking lot somewhere.

You can hook an electrical gauge up to the factory sender. You can plumb a mechanical gauge into the metal t stat housing. I have pics of that if you want.

Huh. What did it cost for the testing? If i do this, it would mean another head gasket kit, another pack of bolts, plus the testing. Also, i would need to find a competent shop to do the testing. Then, if i find a crack, what do i do? Does that mean head replacement? If so, what is the best way to go about it?

Just trying to figure out my options, etc.

Thanks

You haven't found your problem yet so yes this may be required. Do it right next time and use ARP head studs so you can re-use them if you need to. And yes it means head replacement if they find cracks. A new BMW casting is around 1,600, or you can take a chance on a used head.

If it is a head crack it will only leak when it is hot. It takes the heat to make the metal expand to the point that the crack opens up.

These cars need the shrouds around the radiator and the undertray to cool it like the factory intended. Removal of these shrouds will adversely effect it quite a bit more than you would think. I would try removing the puller fan and putting the factory inside shroud back on and go thrash it in a parking lot somewhere.

You can hook an electrical gauge up to the factory sender. You can plumb a mechanical gauge into the metal t stat housing. I have pics of that if you want.

The inside shroud is still present(and attached to the exp. tank.

The front (outer) shroud is gone. I didnt see what good the outer shroud would do. Also to note: the underpanel has been gone for years.

I think i will install a gauge into the thermostat. I'l just keep it loose in the cabin.

Can someone tell me the cheapest and easiest gauge to install?

You haven't found your problem yet so yes this may be required. Do it right next time and use ARP head studs so you can re-use them if you need to. And yes it means head replacement if they find cracks. A new BMW casting is around 1,600, or you can take a chance on a used head.

Ok, so if i pull the head again, does it need to be disasembled to test it? I assume the cams must be out, but do the valves need to be removed?

How frequently do blocks crack and cause this? How would i test for this?

Also, should i used an MLS gasket? I had the head decked to MLS standards, but the block hasnt been touched.

Thanks for the info.

Huh. What did it cost for the testing? If i do this, it would mean another head gasket kit, another pack of bolts, plus the testing. Also, i would need to find a competent shop to do the testing. Then, if i find a crack, what do i do? Does that mean head replacement? If so, what is the best way to go about it?

Just trying to figure out my options, etc.

Thanks

Since the head is aluminum, I'd think it could be repaired/welded. I guess it depends on where the problem is.

I'd check with Bimmerworld, RRT, HMS, VAC or Diffsonline. They're back your way and could point you in the right direction.

Jay

Since the head is aluminum, I'd think it could be repaired/welded. I guess it depends on where the problem is.

I'd check with Bimmerworld, RRT, HMS, VAC or Diffsonline. They're back your way and could point you in the right direction.

Jay

What about the idea of getting a reconditioned stock cylinder head from VAC? I wish i just knew what the problem is. I dont want to buy a head, then find out that isnt the problem.

Right now, my plan is to pull the thermostat, and test it. I havnt done that yet, but i doubt its the problem, because the radiator is definetly getting tons of heat (both fan switches are firing- 190F at the cold side of the radiator). Then, i may wire in a temp gauge to the thermostat housing. I will put back the front shroud, and find a parking lot to blast around to see if i can repeat the condition. I havnt been able to repeat it on the street yet, although the first fan usually runs almost continuous on hot days, and that fires at 176F, which means i have to be at least at 190F at the motor....

What temp should i look for as a maximum if the car is running correctly?

I just went thru a cracked head ordeal on a 91 525, Non vanos. I ended up getting a used one off ebay..$190.. then spending $300 to have it rebuilt.. Its working great.
I took the old head to 2 places. Since they almost always crack between the coolent channel and a valve there really is no good way to fix it. Since the valve seat needs to be pressed in. They told me it worked for a while then the seat came out..

It took me 2 days to get the system bled. I took a hint from the old 3.5 L engines and drilled a small hole in the thermostat. This lets the air get through. I also bled the system. Then drove it for 2 days , bleeding the sytem when I got home. Seemed to solve the problem, its now running at 1/2 vs 2/3 with the air..

B