40 replies to this topic

[OllieH]

I'm beginning to start way more threads in here than I'd like to!

Anyway. I was driving home from work, and as I pulled off the dual carriageway, I lost a bit of power and the engine seemed to be only firing on 3 cylinders, it seemed to chug a bit and didn't sound particularly healthy, missing a bit of the usual grunt.

I got home and checked all the plugs, they all seem to be sparking okay (I had issues with no.2 a few weeks ago) I checked the oil filler cap and there was exactly what I didn't want to see, creamy build up (Possibly caused by condensation? It's been super cold recently. Or many short journeys?) The radiator was at a reasonable level and all looked okay.

What's my best course of action to either rule out or confirm my head gasket fears? 😕

And, how much is my bank account going to hate me if it is the case?

Cheers.

[minidaves]

do it yourself with  a head skim if needed £110 with an oil change

[OllieH]

How difficult a job is it? I can't say I've done anything as big as that before.

[Swift_General]

Do a compression test. This won't tell you that there definitely isn't a problem with the gasket if the readings are fine but may confirm there is an issue otherwise.

Are you loosing water?

[Down&Out]

Its not difficult, if you know your way around a spanner. It normally takes me 2 - 3 hours, if you're careful and you allocate a day you could more than likely do it yourself. If not, its probably a few hundred quid + vat at the garage.

[RHDmini74]

If you decide to do it follow these steps. I found this on another thread and saved it on my computer for when I swap heads on my motor. Good to follow along.

1. Disconnect the earthstrap / negative terminal from the battery.

 

2. Remove the bonnet, after first marking the fitted position of the hinges to facilitate alignment when refitting.

 

3. Drain the cooling system by removing the cylinder block drain plug and/or disconnecting the bottom hose at the radiator.

 

4. Disconnect the HT leads from the plugs, after suitably labelling them to ensure correct positioning on reassembly. Also disconnect the lead from the water temperature gauge sender unit at the thermostat housing. 

 

5. Disconnect the breather hose (where fitted) from the rocker cover, and remove the air cleaner assembly. 

 

6. Disconnect the distributor vacuum pipe, fuel hose and engine breather pipe (where fitted) from the carburettor. On automatic models, also disconnect the kick-down linkage rod from the carburettor. 

 

7. Disconnect the throttle return spring from the carburettor. Remove the two nuts securing the carburettor to the inlet manifold, detach the carburettor from the studs and place it to one side. Where a cable abutment plate is fitted between the carburettor and the inlet manifold, the plate should be removed with the carburettor. 

 

8. Remove the two nuts securing the heater water control valve, detach the valve and place it to one side with the hose and cable still attached. 

 

9. Remove the nuts securing the radiator upper support bracket to the thermostat housing, and the bolts securing it to the radiator cowl, and remove the bracket. 

 

10. Slacken the clip securing the small by-pass hose to the cylinder head connection, this is located on the underside of the cylinder head, above the water pump.

 

11. Remove the two nuts, together with their cup washers and seals, retaining the rocker cover, and lift off the cover and gasket. 12. On 1275 GT models, remove the additional securing bolt 'A' and nut 'B' at the ends of the cylinder head.

 

 

13. Remove the cylinder head and rocker shaft pedestal nuts, releasing them evenly until the valve spring load on the rocker shaft assembly is released. 

 

14. On models where the ignition coil mounting bracket is attached to one of the cylinder head studs, remove the coil and place to one side.

 

15. Lift off the rocker shaft assembly, then withdraw the pushrods, keeping them in their installed order.

 

16. Disconnect the radiator top hose from the thermostat housing.

 

17. Lift off the cylinder head, complete with the exhaust manifold. If difficulty is encountered in removing the head, tap each side of the head with a hide-faced mallet to free it.

 

18. Remove the cylinder head gasket and discard it.

 

 

 

 

Installation

 

Installation is a reversal of the removal procedure, with special attention to the following points. 

 

a) Ensure that all joint surfaces, especially the mating surfaces of the cylinder head and block, are perfectly clean and free from old gasket material. 

 

b ) If the cylinder head was removed to replace a leaking or blown head gasket, check the mating faces on both the head and block for distortion before reassembly. 

 

c) Use new gaskets where appropriate. A cylinder head gasket set should be obtained, as this will contain all the necessary gaskets.

 

d) Do not use grease or jointing compound of any type on the cylinder head gasket when fitting.

 

e) Ensure the head gasket is correctly positioned. The gasket is normally marked 'TOP' and 'FRONT'.

 

f) Ensure that the push rods are installed in their original positions. Dip the ends of the rods in clean engine oil prior to installing them.

 

g) When fitting the rocker shaft assembly, ensure that the rocker arm adjusting screws locate correctly in the cupped end of their respective push rods. If any work has been carried out on the valves (e.g. recutting the valve seats) the rocker arm adjusting screws should be released slightly before installing the rocker shaft assembly. Lubricate the rocker assembly with clean engine oil. 

 

h) Tighten the cylinder head and rocker shaft pedestal nuts evenly, following the sequence shown in. The cylinder head nuts should be tightened in stages (see haynes manual)

[attachment=20061:attachment]

 

 

i) On models which have the ignition coil bracket attached to one of the cylinder head studs, do not forget to refit the bracket before fitting and tightening the head nuts.

 

j) On 1275 GT models, the additional securing bolt 'A' and nut 'B' must be tightened last. These should be tightened to (see haynes manual)

k) Check the valve clearances, as described previously, and adjust if necessary.

 

l) When installation is complete, refill the cooling system, then run the engine and check for oil, water or exhaust leaks.

[OllieH]

Do a compression test. This won't tell you that there definitely isn't a problem with the gasket if the readings are fine but may confirm there is an issue otherwise.

Are you loosing water?

Well I topped up yesterday with some antifreeze mix because of the super cold weather recently and I'd say I've done around 35-45 miles since then and it's still fully topped up, how rapidly would it lose the water?

[jime17]

You wouldn't lose water if it had gone between cylinders.

Id rule everything else out before suspecting hg failure.

Check ignition system and valve clearances if mis firing.

[Swift_General]

Do a compression test. This won't tell you that there definitely isn't a problem with the gasket if the readings are fine but may confirm there is an issue otherwise.

Are you loosing water?

Well I topped up yesterday with some antifreeze mix because of the super cold weather recently and I'd say I've done around 35-45 miles since then and it's still fully topped up, how rapidly would it lose the water?

Then I'd do a compression test. If you have a misfire there are lots of things it could be especially in this weather and whilst taking the head off a mini is fairly straightforward, it's also lot of work to find you haven't fixed the problem.

[OllieH]

Organised borrowing a compression tool tomorrow. Will update when I've done it.

Edited by OllieH, 21 January 2016 - 08:09 PM.

[floormanager]

Sounds familiar to me.  Recently, I changed my exhaust system (manifold backwards) and re-built the inlet manifold on my '68 S  After the re-fit, car started and behaved perfectly. I took it for a drive and while it started out fine, once I pushed it above 4000 rpm, I started to get a misfire. I limped home and changed all the ignition leads (no change) the coil (no change), the condenser (no change), spark plugs (no change). All the while the misfire got worse and worse, to a point where it is badly missing on idle. I could pull the leads of cylinders 1 and 2 without making much difference. I first suspected an intake leak but there was no sucking noises, which has led me to suspect the head gasket might have gone between cylinders 1 & 2.  There was no sign of oil / water mixing but I could not understand what else it could have been, so I bought all the parts for a head gasket replacement.

 

I stripped off the carbs and manifolds again and was ready to pull the head.  Before I did though and as I did not have a compression tester, I took out the plugs and put my index finger in each plug hole while cranking over the engine.  The crude test confirmed that there was similar compression on all cylinders.  Not convinced it was the head, I replaced everything and started the car.  It ran perfectly at first, then started to miss again.  I played around lifting the dash pots and gave the car a couple of bootfulls of right foot and the misfire disappeared!!  I am still perplexed what happened but I can only think I dislodged some crap into a carb or a valve had got gunked up and stopped sealing.  The car is now running fine.

 

Bottom line- make sure it is the HG before pulling it.  Try or buy a compression tester.  I know I am going to!!

[OllieH]

Thanks. I also forgot to mention the oil on the dipstick is completely fine.

[OllieH]

Compression test. Cylinder 4 - 75, Cylinder 3 - 75, Cylinder 2 - 0, Cylinder 1 - 0

Very noticeable air escaping noise when testing 2 and 1.

[Alex_B]

75psi is very low for the other cylinders, are you cranking the engine over with the throttle wide open until the gauge stops rising?

[OllieH]

Yeah buddy, throttle on the floor. Should be around 140-150 right?