I have a 97 BMW 316i coupe and a while ago it started to misfire slighty in the morning. I changed the spark plugs but still no difference. Someone suggested coil pack?
Since then it has got worse and has overheated a couple of times. The first time it happened, it blew a hose and the garage replaced the water pump. The second time it happened, it just overheated and blew a hose again. All this time it has also been unable to release the pressure from the system. I can leave the car for a couple of days, come back and the pipes coming in/out of the radiator are still full of pressure.
I took it out for a drive the other day and it went into the red in the temp gauge but after turning the heaters on it went back down and remained at normal temp.
The misfiring seems to be getting worse and not just in the morning, it can happen if I leave the car for even just a couple of hours!
There is no loss of coolant, no oil in the water and vice versa. The garage tells me it’s the head gasket but I don’t know enough about engines to be able to be sure what it is.
I’d appreciate some suggestions of what it could be?
What you need is a coolant system pressure tester – most garages will have one and i have no doubt that the garage who diagnosed your cylinder head gasket failure would have used one.
Sykes-Pickavant make a very good one.
The tester allows you to check the filler cap – your mechanic was correct when he informed you that there is a Pressure Vacuum Release Valve (PVRV) in the filler.
When the coolant system reaches a pre- determined pressure the pvrv allows the pressure to be released therefore stopping the radiator hose from being blown off.
The tester also allows you to pump up the coolant system to operating pressure to allow you to check for leaks.
The tester also can measure the coolant pressure when the engine is at normal operating temperature i.e. thermostat open, combined with pumping the accelarator you can then determine if the head gasket has been compromised, the cylinder liner is cracked or the head is damaged or warped. The pressure gauge will increase dramatically when you rev the engine.
Repairs will depend on the results of the tests, as always when you remove a cylinder head you must measure the warp using a straight edge.
If the pressure is remaining in the system you must search for other reasons such as a blocked radiator – normally overheating is a symptom of another problem – heads warp and engines overheat for a reason.
I’ve changed head gaskets before on BMW’s for the same problems your having. You start the engine and it miss fires for a little while and then starts to run smoothly. You may even see a small amount of white smoke(steam) come out of the end of the tailpipe for a little while after starting the engine. Most likely its only on one cylinder that the leak is occurring. They make a kit called Block Check that most auto shops have that will tell you if you have a leaking head gasket. Or the shop can put pressure in the cooling system with the spark plugs out and let it set with the pressure in the cooling system for about 4 hours and then turn over the engine and you they will see what cylinder it is that’s leaking. And while they are changing the head gasket have them put in a new water pump. The water pump has a plastic impeller that comes apart.
The signs of a head gasket failure is light brown sludge in the radiatior / expantion tank (coolant bottle) Or under the cam cover usually you can just look at the under side of the oil filler cap, the sludge is water mixing with oil. Also look for steam or white smoke from the exhaust. Are you sure its not just a burst radiatior or a burst hose? If the head gasket has failed you may have to have the clinder head skimmed if it has been warped due to overheating. saddly this will be well into the hundreds ВЈ400 maybe, It just depends on how much dammage has actually been done. Hope this helps and its not too bad
Before you do what ron e says, get the shop to do a compression test, if compression is down in any of the cylinders then it is definitely a head gasket, if your compression is fine then it isn’t your problem. Many of the other problems that he said, if you have been driving it with a blown head gasket it could cause the head to warp etc and cause ALOT of money in repair bills. Also most higher performance cars like that need to run on high octane fuel, low octane fuel can sometimes cause misfire, but that would have nothing to do with overheating.
You have a bad head gasket, cracked/warped head, or a cracked engine block. The pressure in the combustion chamber is forcing gases into your cooling system. The first check should be on your coolant, chemical test will verify exhaust gas. Next involves removing the head, bad head gasket will be visible and performing a magneflux/sonic test will show hairline cracks in the head. Next do the same procedure on your engine block. After that you will know the problem. Junk it and buy a Corvette.
if its the head gasket you might be able to see bubbles rising into the expansion tank. take off the filler cap when cold and start the engine look inside for bubbles.
Bubbles present head gasket leaking.
be careful of the pressure when you release the cap.
it could be the head gasget if it is it will be expensive to repair
get another opinion from another garage and take it from there
a compression test will let you know if it.s a head gasket or not.