Intake Manifold Gasket Replacement This was the cause of the sizzling noise, burning smell and oil leak!

Unacceptable… strange noises and smells.

I’ve been wondering about this for a while now, such as the squealing noise when accelerating, smoke and a strange odor that seemed to be from under the hood. Furthermore, there was a burning smell coming from the air conditioner vents!

It seems to be interlocked with the boosting system of the turbo when listening to the noise while driving.

I don’t know the principle of the turbocharger, but the boost gauge on my surf that I used to drive before shows that the boost pressure goes up from 2000rpm to 3000rpm where the maximum torque comes out of, and the boost pressure goes down when it’s over that. I think it is linked to the transition of the boost pressure which is peculiar to the diesel turbo.

And the strange smell and smoke when I went up the uphill of the mountain road at a stretch and stopped.

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Is the manifold gasket loose?

According to various sites, the early model 4M40’s have a “blow valve” behind the intake manifold that can deteriorate and cause the boost to fall out.

However! My late model 4M40 doesn’t have that! Looking closely at the manifold area, the deepest part of the engine block is stained black with oil. Is it the head gasket? However, I couldn’t see any evidence of oil mixing with the coolant or coolant mixing with the engine oil.

So, suspecting that either the intake or exhaust manifold was leaking, I decided to unload the intake manifold, which would be easier to remove, with new gaskets for both the intake and exhaust.

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Removing the intake manifold was a surprisingly difficult task.

Remove all the sensors, air cleaners and hoses from the upper left side of the tappet cover to make the job easier. Next, carefully remove the EGR and heat shield from the manifold.

Once the intake manifold is completely bare, it’s time to turn the bolts that hold the manifold in place, but as expected, the second lower bolt is hard to turn!

The other bolts can be turned properly by using extension bars of various lengths, but only the second lowest bolt can be turned without using a universal joint. And the extension bar connected to the universal joint hits the metal hose in the water line!

I could manage to loosen it up, but it’s obvious that it’s going to get in the way of tightening it up.

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When I removed the intake manifold, the source of the noise was revealed.

When I took off the manifold….I knew it….the innermost gasket and the back side of the rectangle was completely blown off and I could clearly see the air and the blow-by blowing out of it. The cause of this must be this.

It’s a strange phenomenon. How come the gasket that was supposed to be sandwiched between the manifold and the block flew off so cleanly?

That question made sense to me right away afterwards!

As I found out when I was working on scraping off the remaining gasket glue…

At the time of manufacture, they were supposed to crimp the gasket and the manifold before the glue dried, but it seems that they assembled the manifold after the glue hardened. So there was a gap between the engine block and the manifold, and the gasket was blown off by the exhaust gas leaking out.

Another thing that bothered me when removing the manifold was that the bolts holding the manifold in place were unevenly tightened. Some parts were hard, some were loose…what’s up with that?

Removing the old gaskets is a lot more work than you might think!

Like the old gasket, it’s pretty hard for the manufacturer to remove the glue that temporarily attaches the gasket to the manifold when they assemble it!

I didn’t have any knowledge about it, so I used a flat head screwdriver and a utility knife to scrape it off… but actually, there was such a convenient thing as a gasket remover. I just realized it now.

You should use these things. It’s pretty hard. It’s not easy to remove.
If you don’t remove the gasket, it will cause another boost leak.

The removal of the old gasket and glue will be the key to this project. This is the key to this job.

The fastest way to assemble a manifold

After thinking about how to put the gasket and manifold together, I decided to use some kind of glue to put the gasket on the manifold first, like the manufacturer did. So I used regular instant glue.

Since it was the middle of winter and it was cold, it was not easy to stick it to the manifold. But somehow I managed to get it to stick, and then I had to assemble the manifold before it was completely dry so I wouldn’t make the same mistake as the manufacturer… and then I had an idea!

Wouldn’t it be easier if you put a bolt through the manifold from the beginning?

Fortunately, all the extra stuff around the manifold has been removed, so you can get to the head without having to tilt the manifold. Gently tighten the two bolts at the back and front of the manifold. Pre-tighten the other bolts as well. Why do we need to tighten the other bolts temporarily? Actually…

I couldn’t get the bottom two bolts to tighten properly.

When I disconnect the metal hoses, they leak coolant! So be sure to prepare coolant in advance!

The bottom two bolts are difficult to insert with my fingers, and when I tried to insert them into the socket with the universal joint connected, I had to remove them because the metal hose for the coolant leading to the turbo inevitably got in the way. Although.

As soon as I took it off, water gushed out of it. I hurriedly reconnected one of them and put some appropriate stuffing on the other one, but it didn’t stop completely. I decided to insert the second lower bolt in that condition.

I worked carefully so that the bolt would not fall off, and inserted it safely. Carefully tighten the bolts to the same torque for all 8 bolts. Be careful not to over-tighten! The head is made of aluminum and if you over-tighten it, you’ll fuck it up!

Impressions after the restoration

I’m going to assemble everything and start the engine.


Best engine start! After that, I went back and forth about three times on the usual mountain pass (laughs), but the “swooshing” noise was

It’s completely gone.

The smoke in the engine compartment is….still a little bit, but that’s probably due to the oil stains and other things that are still burning. I think it will go away gradually.

I should have used a parts cleaner to clean off the gaskets during the gasket replacement process, but unfortunately, I was out of parts cleaner, so I couldn’t do it.

The most surprising thing was the engine noise. It got better and quieter… I guess it was knocking. The engine couldn’t take in a normal amount of air if the boost was lost. It was a bit of an abnormal combustion.

A 4M40 engine with no problems is the best!

Gasket replacement, then

It’s still good. No more blow-by-oil buildup. And the smoke and odd odor after high load operation is completely gone! No more oil leaks of any kind.

I wonder what the cause and effect of the blow-by oil not building up in the oil catch tank is. I wonder if it has something to do with abnormal combustion.

Anyway, I’m very happy that the problem that has been bothering me for a long time has been completely solved. Another step closer to a new car?

<Working data>.
Work: Intake manifold and gasket replacement
Expenses: gasket cost? Dollars?
Work time: about 6 hours
Something I noticed: you should have some coolant (about 2 liters) on hand to replenish it.

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