Blown Head Gasket???

[Johno]

I am getting a check coolant level when I shut off the engine. The level is fine.


About a year ago it came on and I bled the system and replaced the sensor. It stayed out until October. I shut off the car and the coolant level light came on. It stayed off for a week.

Then it started to come on every other time I shut off the car. All the while the level is OK. So I bled the coolant and the light stayed out until a few weeks ago.

Now the check coolant warning is back.

Two days ago I removed coolant until it was right at the full cold level. Now the light comes on every time I shut off the engine.

Is this just a simple case of the sensor being bad again, or does it mean air is getting into the system?

In any case, I don't see how the reservoir level sensor knows whether the system is bled or not.

When I take off the radiator cap after the engine has been running there is a slight hiss.

Any insights would be appreciated.

[a32guy]

Is your upper hose rock hard? Does it stay hard after you shut off your car?

[Johno]

No

It is not rock hard.

It gets stiffer.

I see no other weirdness other than this damned coolant light.

I am in terror that I have a slight amount of air getting into the coolant.

But, how does the coolant level sensor know there is a need to bleed the system?

[Neil]

From what you've described, it does not sound like a head gasket problem.

Neil

[Johno]

Thank you Neil.

I am re-bleeding the system now.

Or is this a sensor problem? I have a new sensor but that is more of a PITA than bleeding, so I hesitate replacing the sensor when the nights here are 14 degrees.

What I don;t get is why it needs to be rebled. Thre is no sign of any coolant leak.

[bmwtch8]

Yea, def not a head gasket problem. If it was depending on whether the gasket blew in or out. You would either have extreme pressure in the system which would push the coolant out of the bottle. If it blew in you would have coolant mixing with the oil. Check you dipstick and make sure its not looking like chocolate milk just to be sure.

[mad skilz]

I have been trying to track down the same kind of issue with the obc saying I am low on coolant intermittently without being low on coolant.

sounds like an electrical issue, not a bad headgasket. I replaced the sensor once and it fixed it for a while but its back.

anyone know if the coolant level sensors are known for going out often?

[Fender13Bender]

Mine does the same thing, comes on sometimes after I shut it off and sometimes before I start it, hit check, then it's all systems go, check control ok.

[Johno]

my oil looks normal

I changed my coolant sensor a year ago.



It sounds like several of us are having a similar problem. Let's hang together and get it fixed.

[Volcom8190]

i had this issue, coolant wasnt pressuring, head was cracked, rewelded and then the weld cracked (all before i got the car). i was baffled until i took the head off and realized that was the issue, new head and i was all good. Not saying that this is your problem, but it could be.

[Fender13Bender]

Hmm, I sure hope it's not my problem. I think it's just the sensor.

[a32guy]

I noticed the sensor issue first when my head gasket was saying 'see ya'...

[m3boost]

The floater has a hard time floating on watered down coolant..drain some of your coolant and add about half gallon of bmw antifreeze.. or you might just have a defective sensor..

[Johno]

I just bled the system and ran it hard. The light stayed out this time.

My upper hose was semi-stiff after the drive.

I am stumped on this coolant system and have some questions:

The bleed procedure calls for topping it off and keeping it topped with engine running and releasing air from the bleed until it's all coolant. Then you put the radiator cap onto a full reservoir. So how is there space in the reservoir again when the engine cools?

How is there any coolant behind the bleed screw when the system is cold and the coolant is at the kalt line?

If the reservoir is part-full of air, where did that air come from if the coolant was topped off during the fill procedure?

This whole business of having to bleed a cooling system is just weird. None of this bullshit on my 70 Cutlass.

Why does there have to be a bleed screw at all? What is the need for that?


I noticed the sensor issue first when my head gasket was saying 'see ya'...

How many m iles on your car when the gasket blew? Any other symptoms beside a check coolant light at shutoff?

Is there a test for a minimally blown head gasket? It must not be too bad of a gasket leak if there are no other symptoms. (I am still praying for Neil to be right.)


The floater has a hard time floating on watered down coolant..drain some of your coolant and add about half gallon of bmw antifreeze.. or you might just have a defective sensor..

My coolant is strictly 50:50 distilled water and BMW coolant. Why do you suppose the coolant is watered down?

[SiGmA]

I keep my tank fuller than the line, I've never had a sensor warning. If you are still worried, test the coolant for traces of hydrocarbon. They sell kits at most autoparts stores. If it shows nothing of concern, either run the tank a bit over full, or resistor the sensor...

[Johno]

Thanks




resistor the sensor...

How does this work? What resistor?

[SiGmA]

Actually, I think e36 level sensors are open/closed, so you could just put a piece of wire across the sensor connector, with the sensor disconnected. Newer cars require a resistor in place of the sensor.

[RK-Tunes]

Actually, I think e36 level sensors are open/closed, so you could just put a piece of wire across the sensor connector, with the sensor disconnected. Newer cars require a resistor in place of the sensor.

yup thats how i did mine

[Eric BMW]

Mine does the same thing, comes on sometimes after I shut it off and sometimes before I start it, hit check, then it's all systems go, check control ok.


Same here. Turn car on. "Check Coolant Level" comes up on OBC. Wait a minute. It disappears on it's own. Anyone have insight on this?....I mean after someone answers Johno's question.

[SiGmA]

Same here. Turn car on. "Check Coolant Level" comes up on OBC. Wait a minute. It disappears on it's own. Anyone have insight on this?....I mean after someone answers Johno's question.No. I've seen it on a few cars. Most of the time, a new sensor and a bit more coolant takes care of it (about halfway between the top of the tank and the line), but my ex's 325 suffered the same issue even with a new sensor and a full tank. It was intermittent, but annoying none the less. I expect a jumper on the connector will solve any annoying messages.

[Johno]

Same here. Turn car on. "Check Coolant Level" comes up on OBC. Wait a minute. It disappears on it's own. Anyone have insight on this?....I mean after someone answers Johno's question.

Eric

Mine is happening when the engine is shut off.


No. I've seen it on a few cars. Most of the time, a new sensor and a bit more coolant takes care of it (about halfway between the top of the tank and the line), but my ex's 325 suffered the same issue even with a new sensor and a full tank. It was intermittent, but annoying none the less. I expect a jumper on the connector will solve any annoying messages.

OK,

Last night it worked fine with the coolant level high, and I leveled it to the Kalt line this morning before driving and that damned ckeck coolant comes on every time again now.

I am going to replace the sensor -- again.

So I am under well-deserved suspision for thinking The End is near when it may just be a $30 sensor.

Is a creamy oil cap normal when the engine is cold?

[SiGmA]

Just run more coolant, I don't think it will boil over, my cars nor my customers ever boil over when being ran near the top of the tank.

[Johno]

Thanks again for everybody who is being polite about my worrying.

I just did a test for combustion gas in the expansion tank -- negative.

So it looks like Neil and others were right. (Thank God.)

However, after shtting off the car -- with a new sensor installed -- the damned light came on again.

So I unplugged the car's original sensor plug from the Eurosport splice that senses coolant level in the intercooler tank -- and with the factory sensor plug in the factory expansion tank sensor the light no longer comes on. At least in the last two shut-offs.

This leads me to believe that the Eurosport system has a bad coolant sensor, or there is coolant leaking somehow from the intercooler.

[Neil]

Johno -

The system is incredibly robust and well-engineered.

My kit was, as you know, an early one -- so I don't have a sensor for the intercooler coolant level... and I've never missed it!

I've never worried about a coolant leak, but it's easy to unscrew the port on the top side to check the level if you're so inclined.

Neil

[raghead88]

Air in your coolant will raise your cars operating temperature.
so if the temperature stays in the right range and doesnt overheat, i would look in the wiring between the DME and the sensor. find the values for the sensors signal voltage at the DME and backprobe the DME with a voltmeter while the coolant light is on. I would also find the specs for the sensors resistance and use an ohm meter on it.

hope this helps, pm if you have any questions

[milKt]

This leads me to believe that the Eurosport system has a bad coolant sensor, or there is coolant leaking somehow from the intercooler.

You checked the big fat hose on the back side for any coolant residue?

[SiGmA]

I somehow missed that the TS has a coolant sensor. Good info. I bet that's the issue right there.

[Johno]

Update -- With factory wire plugged into factory sensor the check light stays off for about 10 drives now. The problem was in the TS coolant level system, apparently.


Johno -

The system is incredibly robust and well-engineered.

My kit was, as you know, an early one -- so I don't have a sensor for the intercooler coolant level... and I've never missed it!

I've never worried about a coolant leak, but it's easy to unscrew the port on the top side to check the level if you're so inclined.

Neil

Neil, You are dead-on correct about the engineering. Josh is a genius. The weird thing about the fill port on the intercooler is that if I top it off, the level goes down; it seems to require some space in there. It comes out the overflow spout under pressure I believe. Are you saying you can top off the fill tube and see coolant at the top a drive or so later? I can not; my level drops to where I can not see it, and requires about 4 ounces or less to top it off again. INtercooler system seems to be working fine.

While the kit is good, the customer support is non existant. And there have been several minor problems that absent good information from the vendor I have had to ask a million questions here. To wit: I can not reach Josh to get a part number or replacement for the twin screw sensor wiring. And the bumper has to come off to fix it.

Knowing that I will just drive with the damned thing unplugged.




Air in your coolant will raise your cars operating temperature.
so if the temperature stays in the right range and doesnt overheat, i would look in the wiring between the DME and the sensor. find the values for the sensors signal voltage at the DME and backprobe the DME with a voltmeter while the coolant light is on. I would also find the specs for the sensors resistance and use an ohm meter on it.

hope this helps, pm if you have any questions

I will need to PM you for some coaching on how to do those tests. I will try the neighbor guy first since he know how to use the meter. Thanks for the kind offer. MUch appreciated.


You checked the big fat hose on the back side for any coolant residue?

It is residue free.


I somehow missed that the TS has a coolant sensor. Good info. I bet that's the issue right there.

The only way you could know that is through oral tradition of the dwindling twin screw tribe. There is no documentation of this, and it is not in the instructions. So maybe all my hanky-twisting will help somebody else.

[BadBoostedBmwM3]

I just changed my coolant level sensor bc my car was ginving the "coolant level" message sometimes when i started the car or shut the car off. Anyways, it is good now.

[AA98M3]

Would like to know if the statement that the top coolant hose getting harder is acceptable?
After driving car for a period of time my coolant hose does get stiffer but not rock hard is that normal?