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MG MGB Technical - blown gasket ??

hi and help/advice.
79 mgb, zs carbs.
car runs pretty good, but----------

is there a sure fire easy way ( i'm a novice )
to tell if one has a blown head gasket ??

i would really appreciate any and all answers to
this question!!!
(i do not have access to a 'leak down' tester which i ubderstand is the way to go)

i am not including any of my little symptoms of a possible problem so that i, and all of us, can get all possible answers. i hope this is not a stupid approach, forgive me.
the archives were really of no help.

a really big thanks in advance to you for your many suggestions.

john
john sutter

Compression test is a biggie, but also looking at spark plugs for fouling, looking for oil in coolant, or coolant in the oil, oil/coolant leaking from between the block and the head, overheating, oil burning, blue smoke or white smoke from the tailpipe - it would in fact be very helpful to know what the symptoms are to aid in diagnosing it. Without symptom evaluation, you could pull the head and have a look, that would be the only sure-fire way to know.
Many of the symptoms I described above are possibly indicative of other problems, as is the compression test, so bottom line is, I don't think there is a single sure-fire test of blown head gasket other than removing the head and checking it out.

HTH - Erick
Erick Vesterback

Bad form to ask a question like this without giving symptoms, since we could go on forever and you'd just get confused. The most common first symptom of a bad head gasket on a B is water leaking out the right side above the distributor - and into it!
FRM
FR Millmore

If the head gasket has blown between a water passage and an oil passage you may get water in the oil or oil in the water. In a case like this the compression test or leak test will not show a problem.
John H

Any reason why you think it has blown?
D O'Neill

John, I agree with FRM here - it would be real helpful to see your actual symptoms.

R.
Rick Stevens

The most common symptom in my experience is a pressurised cooling system blowing water out of the overflow and having a stream of bubbles in the header tank. But you really must tell us what your problem is and let us diagnose the problem.
Iain MacKintosh

Wet spark plugs are a quick way to determine if you have a head gasket problem. It will likely be noticed on number 2 or 3 spark plug. Like the comment above, look at the point where the engine block and cylinder head meet above the distributor for signs of coolant leakage down the block. Start the engine, let it idle and squirt some soapy water along the seam between the block and head and watch for bubbles. Compression testing is the sure fire way to determine if you have an imbalance of compression and satisfactory compression gauges are quite cheap. I think I bought one at some auto store for $20. It's a cheap investment and you'll use it many times throughout the life of the car, so I would advise purchasing one. Keep in mind that a compression imbalance could be caused by valve or ring problems and not necessarily conclude a head gasket problem. By what ever method you choose to determine it, your first course of action is to properly torque the head down (make sure you check the manual and follow the proper sequence) and see if that takes care of it. Ideally, you should replace the gasket and have the head looked at for valve problems and checked for warpage or cracks. By all means, don't buy a cheap head gasket if you decide to change it. Make sure it's a good quality copper head gasket from a reputable source. I've made the mistake of installing cheap head gaskets and had to redo the work.
Rick Penland

hi again
in answer to some of your questions about my symptoms.
my only trouble, i think, is a vacuum leak, 15" at idle, which i have not been able to find, it is terribly hard on gas mileage especially in city driving.
so i wanted to get all !! the information, hints, tricks on how to detect a head gasket leak before i try that avenue for the first time.i want to convince myself that i really have/have not a blown head gasket before i do something stupid.
really thanks
john
john sutter

Looking for a vacuum leak takes a different approach.
First, make sure your timing is set correctly.
While the car is idling, take a can of carb cleaner and spray it around the vacuum hoses, manifolds, carburetor base gaskets and shaft bushings, etc., until you notice a difference in the idle.
Look at the spark plugs to see how the motor is burning. http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html
What is your fuel economy?
When was your last tune-up?
Have you done a wet and dry compression test?
Do you have a Bentley manual?
Kimberly

An easy way to check for head gasket leaks is to use a radiator tester [Auto Zone will loan you one] make sure the radiator is full,remove all your spark plugs,pump up the radiator and watch the tester guage when it drops spin the motor over while someone watches the spark plug hole for coolant. A ptece of white printer paper over the plug holes will sometime show a green mist that the eye "almost" sees. RIC
Ric Lloyd

Most common causes of low vacuum on stromberg/catalyst RB models are at the manifold, not inside the engine. Two probable issues:

One: the catalytic can clog, which causes enough back pressure to lower your vacuum surprisingly far, even at idle. If the engine doesn't like revving up and hates to be at full throttle, you're likely clogged. If it runs well at full throttle but hates idling, see Two.

Two: intake manifold gasket leaks are common on these. The single intake/exhaust on these cars is prone to warping. Or, you might just have a leaking manifold gasket. If you pass a compression test, and there's no water in the oil or anything, then you should assume the engine is OK.

(it's possible to test for vacuum leaks by spraying carb cleaner on things while the engine idles; you'll hear an improvement when you find the leak - or you might be able to hear it over the screaming objections of every purist who hates the idea of spraying stuff all over your engine. Fair enough. If your vacuum lines check out, then just go ahead and pull the manifold.)

With the manifold on the bench, Check that the ports are square - put a straight edge across the five ports and see that they line up, as often once the thing has been overheated these will no longer be in line, ensuring leakage. While you're at it, check that it's not cracked, etc, and check that the studs holding it down are in good shape. Often manifold gaskets die simply because the studs loosened up or somesuch. Don't torture yourself - use new hardware! Then, reinstall the manifold *carefully* using a good non-cheapo gasket and high-quality (i.e. not silicone rtv) sealant. (the brush-on copper stuff worked ok on mine) That'll give you a good manifold gasket seal and you should no longer have trouble with vacuum.
Sam

This thread was discussed between 01/03/2007 and 11/03/2007

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