engine problems - HELP

[marcpgl]

Hi everyone,

my d40 is an '07 model, about 140,000km on the clock. Took it in to get serviced and the mechanic said he thinks it has a cylinder/head problem.

Heres the details

- Rough Idle
- 1st and 2nd low range is jumpy on take off sometimes
- Small amount of pressure built up in radiator
- Compression tested, cylinders 1 and 2 read 320 and 308 respectively, with 3 and 4 reading 380

My original mechanic has said its the head gasket, and said may aswell do the timing chain while the head is off, he has quoted $3000 total.

I just rang another mechanic to have ask for their price, and he said compression lower on 2 cylinders generally doesnt mean a blown head gasket?

Could anyone share some advice, and also what would be a fair price to pay for head gasket & timing chain kit?

Thanks!

 

[Old.Tony]

I don't think it's the component cost but the amount of work involved, especially with the timing chain.

Best thing to do with the timing chain - if you're looking at replacing it - is go grab one from yd25.com.au (if you ring them, ask for Paul and tell them you are a member of this forum). He'll ship you a double-row chain, which will never need replacing - the single row shipped from factory is nowhere near as strong.

With the varying compression rates, it could mean a couple of things.

First, there's definitely something wrong. Compression (in psi) is supposed to be 363 minimum, and the largest variation across cylinders is 71psi. You JUST exceed that different in Cyl2->Cyl3&4.

There's a procedure in the manual (download it, it's worth having) on page 237 of EM.PDF. Basically it says you should:

* Remove all glow plugs after cleaning the area to prevent debris from entering the cylinders

* Conduct the compression test

* On the lower cylinders, pour a small amount of engine oil into the cylinder and test again. If the pressure rises, it's probably piston rings/bore damage. If not, it could be valves. If pressure is low in BOTH front cylinders after applying oil, it's probably the gasket.

Now if it's the gasket, you'll need to replace the head gasket, the engine oil and the coolant.

Head gaskets can be purchased from Nissan for around $ ... wait, do you have a first-born? Try sending a private message to Nizzbits on this forum for a better deal.

 

[06nav]

Old.Tony where is this manual I keep reading about?

 

[Old.Tony]

Try looking in the first post of this thread. Link worked a week ago when I tested it.

 

[marcpgl]

quick update on this topic;

got the car looked over by another mechanic, they compression tested it and found it was fine for compresseion, they also found that injector 2 had failed and got the injectors replaced, now ute runs alot better.

quick question though, the radiator pressure is still there, i took the cap off after about 2 weeks worth of daily driving (around 500km) and there was obvious pressure build up in there, coolant flowed out the top of the radiator for a few seconds and then dissapeared back into the radiator,

is that normal? any help appreciated cheers!

 

[Old.Tony]

Did you get the coolant tested for gas contamination? That will tell you if the head gasket is leaking combustion gas into the water jacket.

 

[doc]

The cooling system is a pressurised system. When heated, the coolant expands. The pressure in the system helps raise the boiling point of the coolant. So yes - a certain amount of pressure in the cooling system is entirely normal.

I'd be more concerned about those compression test results...that much difference warrants further investigation.

 

[kernels]

If you always check the coolant when the car is properly COLD, I wouldn't expect any residual pressure in the cooling system. There should be an expansion chamber for the coolant to expand and contract into and out of, make sure this is only filled to the high level, not filled all the way up.

It might be a good idea to redo the compression checks by a third party to see if they actually are an issue. It's always possible that there could be a tiny leak into the coolant system from a cylinder. As OT said above, analyzing the coolant will tell you.