If you have read some of my article or watched some of my YouTube videos, you have probably realized that I love BMW’s, but if I could identify the most consistent issues with the BMW E36 it would be the coolant system. Problematic coolant systems are not limited to the E36 series either, it’s a consistent complaint among BMW 3 Series owners that has continued with the F30 Generation.
Couple a problematic coolant system with an aluminum engine head and less than satisfactory heat dispersion, and you get a car that is susceptible to blowing head gaskets and warping the engine head. Neglect to maintain the car’s coolant system & drive on an overheating vehicle & you’ll quickly have a couple thousand dollar tab on your hands.
In this article I will discuss how you can identify that your vehicle has a blown head gasket, how you can prevent it from occurring and finally some tips on head gasket replacement.
A month ago I left my brother my daily driver E36 while I attended law school in another state. Took about three weeks for me to get the call that the coolant reservoir had blown and the car appeared to have a blown head gasket. After shaking my head at my negligence for not changing out the reservoir, I got excited at the fact that I would have a project to do over my winter break. Needless to say, I’m going to have a solid amount of work to do now when I get home in December.
In this article I’ll discuss symptoms of a blown head gasket, tests you can perform at home & how to avoid ever having to change a head gasket.
If you are interested in checking out one of my favorite must have BMW tools (a great scanner) you can find it by clicking here.
If you’ve pulled a head before you know that there are numerous passages and ports running into the head. Coolant, oil and of course the main airways. Head gaskets can leak in different ways and show different symptoms.
Coolant in oil/oil in coolant
This is generally the most common symptom of head gasket failure. However, you can’t limit your search for symptoms to the typical “milky oil” sign, as some head gasket failures will not have this symptom.
I bought my first junk e36 several years ago for $500. The guy said it was overheating, so I immediately suspected a head gasket failure. When I did my due diligence prior to buying, the only thing I checked in regards to a blown head gasket was the oil. There was no sign at the time that it was mixing with oil, and I figured it was hard to go wrong on a $500 BMW with 100k in miles anyway. After I had it towed home I decided to drive it around a bit. Lo and behold once I parked the thing it had milky oil. The point of the story is you can’t always expect that a blown head gasket will immediately show coolant leaking into the oil.
Oil Cap Milky?
****Cautionary bit of info about coolant in the oil. Beginners unfamiliar with these cars will pull the oil filler cap off, see that it looks milky on the cap and believe they have a head gasket leak.
This is NORMAL, especially if the car is driven mainly for short trips.
Coolant getting into combustion chamber/white smoke
Got a coolant leak but you can’t find the source of it? A blown head gasket can cause coolant to leak into the combustion chamber & burn off, sometimes resulting in white smoke.
**It’s perfectly normal to see a little white smoke from your exhaust when you first start your car in the morning, especially in cold weather! Of course, if the white smoke persists at full operating temperature I start to get very worried.
You will also notice the vehicle overheating and the coolant level dropping. Overtime this issue will tend to get worse & worse until you can already move the car down the block.
Additionally, if you are getting coolant in a cylinder, at least one of your spark plugs will be bleached white.
***Caution, there are quite a few coolant lines running underneath the intake manifold that are difficult to see. A mysterious coolant leak is meant to be identified as a possible symptom, not a certainty that you have a blown head gasket!
Bubbles in the Reservoir
Another simple symptom to look for is air bubbles rising to the top of the reservoir. When the car is cold you can pop the cap off and rev the motor up a bit. If you see a large number of air bubbles continuously rising through the reservoir there is possibly a head gasket leak.
Identifying symptoms is a good first step in determining a head gasket problem. However, if you are going to spend the hours of time it takes to replace or pay a mechanic to replace one of these you want to be 100% certain that you’ve got a blown head gasket. The two most obvious tests to perform in order to determine a head gasket leak are a leak down & compression test.
Leak Down Test
A leak down test is reliable at checking the cylinder pressure in your engine. Although leak down tests can point toward a bad piston ring or valve, a bad head gasket can also cause a loss in cylinder pressure.
You’ll need a cylinder leak down test kit & an air compressor for this test. Leak down test kits can be purchased at any local auto store or your friendly neighborhood harbor freight.
This is a very reliable test if you suspect a head gasket problem. It involves pressurizing each individual cylinder with compressed air and measuring the amount of leakage out of each cylinder.
While a cylinder is pressurized, open the cap of the expansion tank and listen for a hissing sound. If you hear a hissing sound, this indicates a cracked head or failed head gasket.
This test can also be used to identify piston ring & valve problems.
You can pick up a leak down test here.
Cooling System Pressure Test
This is a reliable test at checking a head gasket leak, and quite simple to do. However, you will probably need to purchase the adapter online. You will need a cooling system pressure tester which most auto parts stores rent out!
Use the tester to manually pressure your coolant system, and then watch it for several minutes and note how much the pressure drops. The drop over two minutes should be very slight, only 1.5 psi or so. Significantly more than that and you have a leak. An external leak will be made quite obvious from this test, but if there is none, you have a blown head gasket.
Personally, I don’t like this test very much at all for head gasket leaks, however it’s certainly a little better than guessing. It’s a great way to identify overall engine health, but it’s much more suited to checking the piston rings & valves.
I’ve been talking about symptoms & tests for head gasket leaks. Now I want to just mention the two most important things you can do to avoid ever having to worry about a head gasket leak.
Preventively replace coolant system parts
As I’ve mentioned before, BMW E36 coolant system components are notorious for issues. Every 50-60k I recommend replacing the water pump, thermostat, radiator hoses, & expansion tank. If you live in a city replace the fan clutch as well!
Your highly unlikely to ever see your vehicle overheat if you replace the coolant components preventively, and overheating is the number one cause of head gasket failure.
Check out a separate article I’ve written up exclusively on tips for maintaining your coolant system.
Cut the car off when it overheats
The second thing I can tell you is don’t attempt to drive the car home once it’s started overheating, even if it’s a mile or two. The gauge on the cluster is slow, and once the needle has started moving right of center your already at risk of blowing a head.
If you absolutely have to keep driving, try and keep a speed of thirty and above, and blast the heat!
Tips for Replacing the Head Gasket
A complete tutorial on replacing a BMW E36 head gasket is outside of the scope of this article, but I wanted to mention some important considerations and tips to help you if you are intent on replacing an E36 head gasket yourself. This is the most difficult job I have performed on an E36, there are a number of parts you must remove to replace the head gasket. If you are comfortable with working on vehicles and have some more advanced work under your belt I think you can replace a head gasket just fine. However, if you usually restrict your work to oil filter, spark plug, and fuel filter replacement I would strongly suggest paying a mechanic to do this job.
- The six nuts holding the exhaust manifold to the head are a 1-time use only.
- Take the engine head to a machine shop and have it inspected for cracks and/or warping.
- You will need to remove the cams and valvetrain from the head before you take it to the machine shop or you will need to pay them to remove them.
You can pick up a good quality entire head gasket kit from here (check fit).
Before You Begin
A head gasket replacement requires a lot of organization. You should be prepared to organize the parts you remove and all of the nuts and bolts.
Have a bunch of ziplock bags and sharpies to label them with. All of the nuts and bolts you remove should be labeled.
Masking tape. I use tape to label all of the hoses and wires that I disconnect.
Torque Wrench. On almost any other job you can get away with not using a torque wrench, but NOT on a head gasket replacement. DO NOT think that you can somehow estimate the torque required for headbolts.
If you are like most other Americans nowadays and you own a cellphone that can take a legible picture have it with you. It is annoying to take pictures throughout the replacement process, but trust me, it is extremely helpful and the more you do it the fewer binds you will find yourself in when you have to put everything back together.
Big jobs require expensive tools that you might never use again. Some of them have come in handy for me on later jobs, but I rarely use most of the tools I needed for this job.
32 mm socket, this is only if you have the fan.
Camshaft Alignment Kit with Top Dead Center lock pin
E12 torx headbolt tool
Vanos rigid chain tensioner
Vanos turning tool
Valve spring compressor
Homemade Protractor for Torque Stages 2 & 3
**Overall these tools are not that expensive. In total, they should not cost more than $300. The Vanos tools are extremely useful and you may already have them lying around if you have ever had to fix the infamous “Vanos Rattle.”
Hope this article helped, check out some of my other DIY BMW articles here!