Hilux 4x4



How to replace the head gasket on a 4Y Toyota engine

Original topic, click here - By Snipes

Replacing the head gasket on a 4Y is a pretty simple job, but if it is to last it must be done properly. Also doing the headgasket may not be a difficult job, but it would be a complete waste of time if don't first find out why the head blew, like head gasket failure(old age,deterioration), stuck thermostat, cracked head, blockage in the radiator, broken viscous coupling , etc. If the problem was more than just head gasket failure from old age, then the cause must first be addresses and fixed first.

A basic step by step rundown of the job, please note I may have forgot a step or 2, so any input is welcome:

1. drain the coolant in the block, the drain plug(bolt) is just behind the alternator, below the exhaust manifold.
2. drain the coolant in the radiator by removing the bottom pipe, disconnect the water pipe coming from the back of the head, disconnect the water pipe at the top(between the radiator and head).
3. drain the oil via the sump plug, with a blown head the oil may be contaminated with water. Remember to put the sump plug back, or you may land up wasting 5 litres of new, clean, expensive oil(been there, done that!)... remove and toss the oil filter!
4. loosen the bolt on the powersteering pump pulley, before removing the belt.
5. remove the powersteering belt and alternator belt.
6. remove powersteering pump pulley bolt and carefully wiggle the pulley off the shaft.
7. behind this pulley are 2 bolts, remove them, as well as the one at the rear of the pump steering pump. This should loosen the PS pump from the mounting bracket, carefully remove the PS pump and place it on the chassis below(upright, so it doesn't leak). Secure it there with a piece of wire, so it can't fall off.
8. Remove and the carb linkages, disconnect the electrical plug, disconnect the fuel pipe, disconnect the vacuum pipes(take note/take pics so you know where each vacuum pipe goes for re-assembly), remove the bracket holding the accelerator cable, remove the 4 nuts holding the carb on the intake manifold, remove the carb.
9. Loosen the bolts holding the exhaust and intake manifold in place (can be a pain the get these bolts loose, may want to spray them with a penatrating oil first). Remove the intake and exhaust manifold. You may have to disconnect the header-exhaust connection to remove the exhaust manifold.
10. Unbolt and remove the tappet cover.
11. Unbolt the rocker shaft, each bolt little by little so the shaft is lifted evenly, remove the rocker shaft, the pushrods can be removed one by one, again mark where they came from so they can be returned in the same position.
12. Using a power bar or the like, loosen the head bolts one by one, 5 of them are under the tappet cover. Remove them and mark where each one came from so they can be put back in the same place, also be careful not to leave the washers behind.
13. Under the ignition leads on the head, are 3 bolts holding the head in place, remove them.
14. The head can now be removed.

Assembly is basically the reverse of this process. Have the head checked and skimmed before starting re-assembly. You will need a new head gasket(use the orginal Toy one or a Payen one), a intake/exhaust manifold gasket and some decent gasket maker.

The most time consuming aspect of the job is cleaning all the bits and pieces, and carefully cleaning the mating surfaces on the block, head and exhaust/intake manifolds.

On torqueing the head bolts, once the head is back on, the bolts should first be torqued to 30nm each in sequence(I'll get the sequence from the workshop manual this evening), afterwhich they must be torqued to 90nm again in sequence. You will need a good torque wrench for this job. The head bolts must be re-torqued to 90nm at 1000km.

The valve stem seals will have to be replaced by an engineering firm as special tools are needed, like a valve spring compressor.

The exhaust/intake nuts will probably have to be replaced, as well as the nuts and bolts on the header-exhaust joint.

The thermostat is in an awkward spot, it's in the housing behind the alternator/PS pump, where the lower water pipe from the radiator connects to the engine, it is easier to access with the PS pump out the way.

Super experienced 4Y Hilux fundi's like Simoan and Allan will probably give more advise!