Replace head gasket, compression test

Mxgrds

Mxgrds

True Classic
I am prepairing to replace the head gasket due to gas feeding into the coolant. I have been able to locate the problem in cylinder 3 by doing a compression test and at the same time looking at the coolant level. Only on 3 the coolant level changed and bubbled.

Can I do a compression test without mounting the camshaft? Leaving the plugs out, the belts off. I want to test the new head gasket before I mount the valve head etc. I know, the real test is driving the car. But this might give an indication if the initial repair succeeds. What is your opinion?
 
Compression test of leak down test?

Leak down test will work... as you've got both valves closed on all cylinders.

Cranking Compression test won't work or tell you much as you've got no way for the air to get in to give any real compression.

Cranking the engine with the belt off will also mean no oil pump being driven... as the auxiliary shaft wont be turning either.

SteveC
 
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No air when both valves are closed. Did not think that carefully through. the oilpump not working is a plus. Otherwise i would have an oilfountain.

Need to install the camshafthousing then and the belt before doing a first test.
 
No oil pumping suggests excessive wear on the bearings of the bottom end. The starter can do several hundred rpm which would be bad, especially with little load.

I would just do the leak down test as that will tell you what you need to know, just be sure to have the tested cylinder with the piston at tdc
 
Do you have the head off yet? How about some pics of the old gasket, etc.

Bad idea to crank the motor except by hand with the cam box & timing belt off.

As long as the head is checked at the machine shop & decked as needed, and you thoroughly clean & check the block, there is no reason to assume the new gasket won't do it's job, again, presuming new head bolts, proper torquing, etc...
 
Mxgrds said:
Thanks for the support. Need to find the tools for a leak down test then.
Click to expand...

Easy to do if you have an air compressor, or know someone who does.

If you don't.... If you are sure that you are getting bubble and rising coolant level only when #3 is undergoing compression, I'm not sure how much trouble I'd go to find a leakdown tester. It sounds as if the head is coming off in any case.
 
Cylinder head is taken off. Culprit easy to identify.

20160630_172004787_iOS.jpg


Detail of the gasket:
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What could be the cause? The head was flattened (?). I reused the old bolts. (I have ordered new ones). Looking at the gasket and head pictures. These were taken right after I lifted the head. I wonder why they look a little bit wet on certain places. Could be some coolant dropped from the head.
 
Did you retorque after a heat cycle and then again after a few hundred KM?

Close up pic of the head (like the close up pic of the gasket)

SteveC
 
I know that engines that use an aluminum head on a cast iron block are notoriously hard on head gaskets. This is due to the differences in expansion rates between aluminum and cast iron. I'm not sure this applies to this specific instance, as most failures I have seen look like the head gasket had been abraded.
 
X1/9 Head Gaskets

X1/9 head gaskets are not prone to failure if the head is true, the gasket was properly installed and properly torqued.

I wouldn't worry about running a compression test to verify the repair. Instead, I would have the head checked to ensure it is true, chase the threads on the head fasteners and re-install the head, with a new gasket, as per factory procedures. You should be fine.
 
Too much advanced ignition is possible. I had some idle problems and drove a short time with more then the 10 gr before TDC.

I retorqued, but the gass problem was almost instantly after the gasket change appearent. What i noticed when i took the head of, is that some bolts/nuts went off smoothly and some difficult and with lots of noise. I assume that a lot of torque went into the resistence of the old bolts and buts. And thus not vertical force.

I will later on place a detailed picture of the head.
open
 
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Yes it sounds like you had threads in the block that were not as clean or lubed as well as they could have been, and this gave you a false torque reading... that's why I asked if you had retorqued, because it looks like the head has lifted allowing the gasket to fail...it's most likely to lift in the centre as this is the hottest point, the end cylinders run cooler, number one has the water inlet...so gasket failures are more prone to be at the junction of 2 and 3.

Chase out the threads well... you can buy specific tools for this rather than using a thread tap, which can remove metal from the threads, which you don't want.. something a bit like this...





New bolts oiled and drained, check head for flat and chase out the threads in the block, make sure your torque wrench is accurate, work methodically and you should have no problems... the sohc is not a head gasket eater if good practice is followed.

SteveC
 
Thanks for the advice Steve. I consider myself not as a first class mechanic, so this is well received. Keep you informed.
 
Which style head bolt did you buy ? I ask because the first two times I did mine, I used the standArd bolts that require retorque. This last job, I bought TTY bolts so no retorque would be required :)
 
Hussein,

it's not the bolts only, if you use the TTY method you ALSO need to use a compatible head gasket, the TTY system will not work just relying on bolts.

It need to be a polymer construction style gasket... off the top of my head Fiat 5951682 is the part number for M10 14 bolt style (but would need to check the number)

SteveC
 
Not TTY. I have appearantly an early injection based on the carbarated engine until 1980. So 10 19mm bolts and studs. To be torqued to 69 ft. Lbs in 3 steps. No retorque needed as I understood?
 
No the M12 bolt / stud combination is a retorque style engine, and uses a retorque style head gasket, so absolutely needs a retorque after a heat cycle and again after several hundred Km. Failing to do so will lead to a head gasket failure.

SteveC
 
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