Do-it-yourself overhaul of the Zmz 402 engine

The ZMZ 402 engine, which was produced at the Zavolzhsky Motor Plant, became a real legend in the domestic automotive industry of an entire era. It was installed on many car models such as Volga, UAZ, Gazelle and others. But, since the power unit has ceased to be produced, and its operation is carried out to this day, then periodically these engines need to be repaired.

Any engine wears out during operation, and this happens not only with internal elements, but also outside. This indicator is influenced by many factors that destroy the engine. So, let's consider the reasons why the ZMZ 402 engine needs repair, especially with regard to capital restoration:

The process of carrying out repairs, including overhaul, for the ZMZ 402 engine and its modifications, is similar to other power units of the series. All power units manufactured and manufactured by the Zavolzhsky plant are similar in design characteristics, and therefore repairs are quite easy. So, let's look at how to repair the ZMZ 402 engine with our own hands.

Repair of the ZMZ 402 engine begins with the dismantling of the power unit. The process is fairly straightforward, but four-handed is recommended. But, there is one difference, if the internal combustion engine is removed from the Volga, then this is one sequence of procedures. As for the 402 Gazelle engine, here the dismantling technology is slightly different. In order not to get confused, consider the classic process of removing a motor from a Volga car.

So, what sequence of operations needs to be performed by the motorist, what to remove the engine from the vehicle:

1. First, the battery is dismantled and its shelf is unscrewed.
2. Next, you need to remove the air filter and carburetor.
3. Disconnect the front pipe from the exhaust manifold.
4. We unscrew the spark plugs, remove the wires and the distributor.
5. We drain the engine oil.
6. Disconnect the fuel system.
7. Remove the fan impeller.
8. We dismantle the starter and generator, as well as the wiring associated with them.
9. Disconnect the clutch from the gearbox.
10. Dismantle the oil filter housing.
11. We remove the radiator and pipes of the cooling system.
12. We dismantle the intake and exhaust manifolds.

Further, when everything is disassembled, we completely remove the hood so that you can be unhindered, pull out the engine. We dismantle the power unit by hooking it onto a hoist or winch. Now, we install the motor on a special stand, if there is none, then on pallets and proceed to disassemble it. The motorist needs to disassemble his engine completely.

To do this, remove the parts in the following sequence: clutch, valve cover, oil pan, cylinder head, oil and water pumps, pistons, yoke, crankshaft. Now you can start the procedure for diagnosing the condition of the parts.

Diagnostics of engine parts begins with an inspection of the integrity of the cylinder block and crankshaft. If necessary, the body can be welded with special welding. If the block is very susceptible to destruction, then it should be replaced with a new one.

The next step in the diagnosis is cylinder measurement. The standard for ZMZ 402 is the size of 92 mm. But, if there is an elaboration on the walls, scratches or shells, then you will have to sharpen it to the next size. And if the measurement showed that the walls have already been repaired, then it is imperative to sharpen it to the next one, since the cylinders have a depletion and it must be eliminated.

Consider a table of the dimensions of repairs for the power unit 402 and its modifications:

Actually indications for overhaul 2 - this is an increased consumption of gasoline and / or oil. In principle, everything. Any engine malfunction (and not only, as well as chassis, for example) one way or another will lead to an increase in fuel consumption. At the same time, the car will not lose in dynamics (well, unless everything is extremely neglected, like a burnt-out valve piston). For any car, the manufacturer indicates the normal consumption of both gasoline and oil. In the case of the Volga with ZMZ 402, gasoline consumption in the city should be 13.8 liters per 100 km, and oil should be consumed no more than 250 grams per 100 km.

In my case, the consumption was 25-30 liters, while the oil had to be topped up by a liter per month, with a mileage of less than 400 km. Gasoline consumption was measured by the odometer. As further developments showed, in addition to the wear of the engine itself, a slipping clutch and a wedging brake pad, as well as a muffled EPHH system, also contributed to the increased consumption.

The capital was made a year ago, upon completion of the running-in, it turned out that in winter, with normal driving (without slipping), it fit into 20 liters, in summer the consumption was 14-16 liters when driving with a moderate degree of aggressiveness. During the run-in, the problem of oil leaks was actively solved and by the time the run-in was completed, the engine was switched to synthetics, which it still drives.

The oil pressure before the capital was satisfactory, so I did not plan to remove the crankshaft. Nor did I plan to change the earbuds. From the spare parts, I took a set of valves:

New valve springs. It is imperative to change them with capital, Evgeny Travnikov constantly repeats this, they say tired valve springs squander power at high speeds. It seems to be true, after 3000 the motor with new springs began to pull much more fun.

A re-turning was also planned, for which a set of bushings was purchased.

A set of gaskets was also purchased for the overhaul of ZMZ Zolotaya Series. This set turned out to be a rare gamma, so I advise you to buy separately the valve stem seals, the front crankshaft oil seal, crankcase cork gaskets, valve cover and pusher covers. For all other gaskets, I advise you to buy oil-resistant paronite and cut the necessary gaskets in place yourself.

From the tool you will definitely need:

Torque wrench for 12 and a head for 17 is required.

The mandrel for pressing on the valve stem seals will not interfere:

Be sure to need a 9mm sweep:

The valve dehydrator will make life easier and save the bushings:

One of the most expensive items is cutters:

To remove the cylinder head, first remove the axis of the rocker arms, then carefully unscrew 10 nuts. I had a couple of nuts creaking, so you need to unscrew it smoothly. Important! In order not to distort the cylinder head, the nuts must be unscrewed in the same order as when tightening, little by little. That is, first we pull off the nuts from their place. Then we sequentially unscrew all the nuts, unscrewing them by a third of a turn. Further, all the hope is that the collective farm with the previous installation of the cylinder head was not (such as a stuck solid oil). However, even in the absence of a stuck gasket, there will most likely be a problem with the penultimate hairpin on the passenger side:

The next stage of the overhaul is the removal of resinous deposits from the parts. This is how the cylinder head looked a year before the overhaul, after 1.5 years on semi-synthetics:

Washing was carried out with dishwashing detergent (any will do) using a toothbrush. The technology is as follows - we drip with dishwashing detergent and with three toothbrushes, wipe it dry like the slurry turns black with a paper napkin. And so on, so almost all the details were washed away:

First of all, the washed cylinder head must be sanded:

The combustion chamber was covered with a thick layer of carbon:

Next, remove the old valve stem seals. I didn't have much oak, and a couple were generally cracked:

The next step was to turn over. I wanted to use the technology of Evgeny Travnikov:

The next stage of cylinder head repair is the trimming of the saddles. It seemed to me that only a 45-degree chamfer was cut from the factory, but I cut all 3, which is why the valve should close more tightly and gas exchange should improve. I heard a lot about the hardness of the cylinder head ZMZ 402 saddles, but with the above set of cutters, my saddles were cut quickly and easily. The central chamfer was made in the region of 1 mm so that after lapping it would increase to the prescribed 1.5 mm.

The next step is lapping the valves - this is the most tedious step. I didn't bother much about checking with diesel fuel, etc. assessed visually by an even pattern around the circumference of the saddle. Do not forget to sign the valves so as not to confuse them during assembly.

Also, to improve gas distribution, I grinded down the steps at the valve seats:

At the end of the cylinder head repair, we press on new valve stem seals using a mandrel. IMPORTANT! Before pressing the MSC, put on the lower valve plates, then they will not fit 🙂... After that, you can dry out the valve. Let me remind you once again that the springs must be changed during a major overhaul. The old valves were dirty and worn out - they had both scuffs on the stem and did not protrude enough above the plate, that is, as the rocker arm wears out, it will begin to press not on the valve, but on the plate:

I started the assembly by replacing the tank with a new one from a gazelle, screwing a fitting 18 into it:

In the thermostat, I filed away casting defects with a file, which will improve the coolant circulation by a fraction of%:

I also slightly "screwed up" the oil supply channel from the hole to the support of the rocker arm axis (seen in the photo), there were small burrs:

Then he proceeded to replace the piston rings. Before that, I carefully scraped off the carbon deposits from the piston (it turns out to be aluminum):

Next, we change the gland packing. I bought a cheap one for 15 rubles, changed only in the lower holder, since I did not remove the crankshaft. Despite all this, this 15-ruble packing has been holding TNK 5v40 synthetics for a year with periodic engine promotion up to 5000 rpm. As far as I understand, the packing flows with large beats, with strong wear on the necks and liners.

The next step is to install the cylinder head on the studs, I wound fum tapes, due to the fact that it is Teflon (fluoroplastic), and it is extremely chemically resistant and quite heat resistant. In general, I wind fum tape on all pins / bolts prone to souring, in loaded places it will break and fill the cavities, which is why rust does not form in them. The fum tape itself is not going anywhere:

I put the gasket with triangular windows. From the factory there was the same:

I also applied a little know-how, wrote on my head the procedure for tightening the nuts 🙂:

The primary grinding of the rings was carried out with a barrel organ (crooked starter), that is, when the cylinder head was not yet installed, I poured oil from above into the sleeves and twisted it. That is, what a pause stood out, I approach - 50 revolutions. It became especially tight after replacing the packing, in total I did it with my hands in the region of 500-1000 rpm, as a result, the engine started with a starter without straining. I ran in the same oil that I drove to the capital - semi-synthetics TNK 10v40. While driving, I tried to keep 2100 rpm without spinning more than 2500. Without any dynamic overtaking. Having driven around the city for a week, then made a circle of honor around the city, about 80 km along the bypass road. At the same time, I was driving strictly 2100 rpm in 5th gear - this is about 80 km / h on the railway station, according to the speedometer it was 90. All the time I was running in I was at war with oil leaks, and by the time 1000 km was completed all leak channels were eliminated and I switched to synthetics with a clear conscience ...

Repair of ZMZ-402. Disassembly and troubleshooting

The internal cavities of the engine were heavily contaminated with a mixture of grease and soot, almost a centimeter under the valve cover. When opening the crankcase, the main nut was unscrewed.

The nut was stored in a pallet.

The stuffing was brought up in order, it was installed with a Christmas tree in rotation, i.e. vice versa.

The exhaust valves are flared with fungus.

The camshaft upset most of all, on 4 cams there are nicks, the cams are sharpened by 1 mm.

On the intake valves at the top of the cut.

To measure the stiffness of the springs, such a device was made.

Based on the results of parsing the camshaft for replacement, grinding the knee, valves for replacement. I will cut the head of the ZMZ-402 under 92 gasoline.
Internal springs are within tolerance, external springs are rather weak (46 mm, 23-25 ​​kg).
The piston is in the tolerance, at least not to change something, I will change the ring current.

So, at the moment, I have assembled a block. First of all, I eliminated factory errors in the manufacture of the block, the channel after the pump is clogged with flash and casting defects.

But after using the file, everything goes away.

Next, we unscrew the plugs of the oil channels, and clean the insides with a wire and a compressor; in three channels, the remnants of drilling were found, it looks like they are still from the factory.

We level the sharp edges on the oil channels of the crankshaft so that they do not cut off the liners, the main thing here is not to make a bump along the edge.

I spin the crankshaft, not over my head, but the crankpin plugs.

It got from the crankshaft.

We put a knee and drive in the piston, grease all the mating parts with oil, which I will then fill in for running in.

Tie on two clamps and strips of sheet metal 30 * 290mm

Installation of the ZMZ-402 camshaft.

I put the adapter on the Zhiguli filter, drilled out the oil channel, it was very small.

Adapter for Zhiguli filter.

The pulley spread apart had to be knocked down and grabbed.

I painted the covers from ZMZ-402.

On the left is the Volgovsky bracket, on the right is the UAZ one, for comparison

A Fenox basket was selected, driven by any UAZ one for the desired shaft (they are also different).

For comparison, on the left is an old Volgovskaya, on the right is a new one, at the back there is a lever. I will not say exactly where it came from from UAZ or GAZ, 6 springs, seemingly more powerful than from UAZ. I read from the reviews that the diaphragm link is weaker than the lever one, a small test stepping with the heel into the place of pressing the release bearing with my stunted body of 100 kg, I can say that the old Volgovskaya and the lever linkage bent 1-1.5 cm, and the new nifiga did not bend.

I read that the flywheel on the ZMZ-402 is lighter than on the UAZ (8 kg versus 13 kg), well, figs knows, maybe I have it from old age, but it weighs 13 kg.

And his diameter is like this.

It is desirable that the bell be universal, like mine.

Summarizing, we can say that to introduce the ZMZ-402 from the Volga to the UAZ, it is enough to buy a pressure plate and front engine mounting brackets. Well, the exhaust has to be altered, the gas pedal control… these are trifles.

I also had to change the ring gear, knocked down the old one with a hammer, put the new one in the oven for 10 minutes at 250 degrees, like ten minutes. I lubricated the flywheel with a thread lock in advance and put on a crown. Collected after cooling.

It happens that antifreeze runs away through a hole in the block along a hairpin, this one

Secret hole threaded at 10.

I did not check, but simply screwed a bolt in there.

Collected the cylinder head. The head was sanded under 92 gasoline, cut off 3.5 mm, the height of the cylinder head was 98 mm, it became 94.5 mm (standard 94.4 mm).

The outlet to the stove, the so-called tank, in the rear of the cylinder head rests against the wall of the engine compartment and needs to be removed, and the question arises where to get the outlet to the stove. Well, if there is a sensor in the upper part of the cylinder head, then the question disappears, but in this place I had only a technological influx of aluminum. In short, there is no hole. But the absence of a hole will not stop normal boys, I need to do it, I got married like that in general. Okay enough demagogy closer to the point.
The cylinder head was like this:

I took a 19mm drill bit (I had to take it for 18mm, but it worked out fine anyway) and half-inch taps for pipe threads, they can be seen in the photo, and rushed.

We drill and cut threads, everything is just enough space.

Then I checked the oil channel, it did not coincide a bit with the block, it was filed with a file.

Grinding the mating plane.

I checked the input-output channels for coincidence with the spider, sawed off.

Not a scratch remained on the valves from the purchased lapping, although the belt on the saddle was already packed almost 2 mm, I repeated it with a homemade one made of abrasive, it went a little.

But on the rest, I did not achieve the same effect, I spilled it with a solvent, it didn’t seem to flow and was dry.

In the set of gaskets there were gaskets for everything, I had to do it myself around the back plug of the cylinder head. It is convenient to hit holes with a sleeve 7.62,

For stuffing the caps, a brush came up clearly.

The passage diameter of the angle 15 is approximately 14.5 mm, the tank is 9.5 mm, i.e. the passage in the corner is more than 2 times.

I drove the holes for the engine studs with a 13 mm drill, cleaned out a lot of dirt and removed the aluminum flattened to the thread.

Ideally, the guides would be changed (clearance 0.5 with a max tolerance of 0.25 mm), but it is expensive, and there is no suitable set of tools. On sale, the scans are bad.

The engine is assembled and dries up. The head is screwed on, the valves are adjusted. I drilled a hole in the pump for a half-inch brush so that the coolant outflow from the stove was equal to the inflow.

I drove a sleeve from the shock absorber into the tee to reduce the flow of fluid in a small circle, so that the pump sucks more from the stove.

I screwed all the nuts, pins and bolts onto the thread lock, where it is red, where it is blue, something I like it very much lately.

Disassembly, assembly and troubleshooting of ZMZ-402 completed.

Engine: ZMZ-402.10 1996 release. pistons 1992

Mileage 4600 km. real.

I did not find an article or topic on ZMZ-402.10. There are 406.

After an unsuccessful refueling, I received a breakdown of the gasket in the lubrication system. The oil became very liquid from gasoline. The level was at a minimum. It flowed from everywhere. Candles are black, flooded or dull black.
The engine is removed and disassembled. There is no experience in such matters.
Read books on the operation and repair of GAZ 2410/31029 from this site.

ZMZ-402.10 did not find an article or topic on repair on this site. There are 406. I didn't find anything special about other resources. Close to life in garage repair found the video JfdwOUVrMiEeWf. If anyone shares a useful link, I would be grateful.
Inspection gave the results:
Nagar in the intake system (film), matt carbon deposits in the exhaust, the head, the carburetor turned brownish. There is a lot of carbon deposits on the guides, valve shanks.
On the valve discs, on the chamfers, there is a gray dense coating. Some of the valve chamfers and seats (3,4 cylinders) at the points of contact have a gray coating.
Rings. lay down on cylinders 2,3,4. Soaking in diesel fuel does not give much result. The pistons are washed, but the top 2 rings are tightly clamped. On the 2nd piston, I removed only the lower dial and middle ring - it cracked in half. The reason for the clamping of the ring is rust. I took off this ring for a long time.
How to remove the rings on the remaining pistons?

Piston. There is almost no wear and tear.

Liners. The condition is about the same. Traces of weak hone and slight abrasions in the working area are visible. there are traces of rust in the block at the joints on the aluminum. There is nothing to check the liners for ellipticity. Is it necessary to remove them to seal the fit? Whether to change them or not. How to find out? If you change the cylinder + piston + finger + rings?

Liner [caps 3 connecting rods fell out by itself during removal. The rest are holding on. The connecting rod bushings are worn out (scuffs, minor scratches). An insert that has a hole and a weak groove (groove) in the connecting rod, and not in its cap, from the edge of the insert to the hole. Those. 1/4 of the diameter of the liners.
What's the best? Why is there no groove along the entire diameter? Replacement connecting rod bushings. Which company to take. and is there +0.05 ?

Crank pin. on the 4th cylinder the piston rotates more freely than on the others. there is no backlash. Change?

Crankshaft. On the necks of the connecting rods, the surface is mirror, but there are small scratches. Can I grind it myself?
On the crankshaft main bearings, there are no wear marks, on both halves there is a groove along the entire length. KV has no scratches. There are inclined notches under the packing. Axial clearance 0.4 mm. should be 0.125 - 0.325 mm. Is it worth changing the washer while removing the gear? There is no stripper, and the hand does not rise to knock down.

Gears. The teeth are not eaten, they sit firmly. The marks are aligned and stand according to the book.
I'll leave it as it is.

Camshaft. There are no traces of cracks, no wear - there is a little on the sharp tips of the eccentrics. There is an axial play of the shaft of 0.4 mm instead of 0.15. Need to change the thrust flange? Or can you use a steel washer?

Pushers. Circular groove at the bottom of the last pusher 4 cylinders deep

0.3 mm. Replacement? Others have a polished strip at the point of contact.

Crankshaft oil seal. The drips from the oil seal are not visible. The oil seal seems to be new. Change?
Stuffing. There are no drips from the packing, but the back of the basket is splattered with black grease. Where would it come from?
Replacement oil seal and packing?

Barbells. The length is the same. Spread + -1 mm. on several, the upper end is polished so that the pits in the center are not visible - is this a replacement?

+++ Before disassembly, there was a defect: the KV rotated freely if the candles were turned out and wedged in one place if the candles were screwed in. Where to dig.

What else should you pay attention to?

Added after 12 hours 41 minutes 52 seconds
I used to repair the clutch. Marked everything (disc, basket, even bolts)

white stationery proofreader in a tube with a brush (for correcting mistakes on paper with solvent). I knocked down the balancing only on the way.
How can you balance the flywheel, crankshaft and flywheel yourself? Because it is very far to carry such weights to the repair plant.

See Additionally:
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How to change giza and put a gasket here
assembly features here

The 402 engine is a major problem. At one time, this engine was good, quite reliable and kind of relevant. This is confirmed by the fact that it was exploited for many years. The design of this engine took place over fifty years ago. The positive aspects include the fact that it stoically endures overloads, it is quite competently implemented, and it is very easy to repair it, even on our own.

One of the biggest drawbacks of the 402 engine is that after 1986 its quality deteriorated markedly. Since centerless grinding is still used in old factories, this is accompanied by the fact that the main axis and the bearing axis of the crankshaft do not match. And the crankshafts themselves are poorly balanced, which can lead not only to strong vibrations, but even to engine failure. Another disadvantage is that the rear oil seal was replaced with an oil scraper packing. But, despite all these shortcomings and shortcomings, the 402nd engine continues to operate safely, and with the application of a minimum of effort - for a long time.

Let's imagine a situation that you need to adjust the thermal gaps. To do this, you need to do the following. Initially, we remove the carburetor, and before that, we disconnect the fuel supply pipe in the carburetor, as well as the air filter pipe. After that, having disconnected the drain and delivery pipes, we remove the oil filter. We remove the outlet and inlet pipes. Disconnect the drain pipe of the fine oil filter from the valve box cover. Then we open the cover on the valve box, but very carefully so as not to damage the cork gasket. Then it is necessary to bring the piston of the first cylinder, using the starting handle of the engine crankshaft, to the extreme upper position during the compression stroke.

Now we adjust the clearance: release the adjusting bolt locknut using a wrench; then we hold the pusher from rotation; we check the gap with a flat probe and at the same time rotate the adjusting bolt, while holding the pusher until we get the desired gap. Next, tighten the lock nut and check the clearance again. We adjust the first, second, third and fifth valves, but without turning the crankshaft. The crankshaft must be turned exactly one revolution until the mark on the flywheel is displaced. We adjust the fourth and eighth exhaust, sixth and seventh intake valves, as well as the thermal clearance in the valve system.

After a while, a knock may appear in the engine, or rather the valve mechanism. It cannot be eliminated by adjusting the thermal gaps. The knock is caused by an increase in the axial clearance of the exhaust rocker arms, because they do not have spacer springs that automatically eliminate the clearances. They can be eliminated by placing a washer between the spacer sleeves and the rocker arms on the roller. For this, shims can be used. If they do not fit in thickness, they can be adjusted using a file or grinding wheel.

In this video of the repair 402 engine, the author tells in detail how to disassemble and repair it.

Shows how to remove the valve cover correctly. It also draws the viewers' attention to the condition of the barbells as one of the frequent breakdowns and explains why they need to be changed.

Step by step disassembling the engine, the author draws his attention to the fact that all mounting parts must be in car oil. When disassembling, all channels must be cleaned, and if there are potholes, they must be sharpened. You also need to pay attention to the valves, they must be clean and not burnt out.

As it turns out on a video campaign, the whole reason for the breakdown is a malfunction of the camshaft drive gear.

The author does not forget to tell how the oil pump is removed, how the flywheel and pulley are removed correctly.

Draws attention to the piston, apparently, it has recently changed, although one of the rings is already broken. This suggests that the previous master overdid it a little.

The author carefully demonstrates the disassembly of the 402 engine down to the smallest details and elements. Shows how and how the parts are removed correctly, tells how they work, why they serve and what can cause them to break down. This video can serve as a good lesson and example in order to deal with the engine yourself at home.