The Mitsubishi Pajero Owners Club®

jimmy · Posted: Fri Dec 24, 2004 12:51 Post subject: EGR and head gaskets.. a Poll

Having just had to replace my cylinder head and head gasket, and having had the EGR valve blocked for 2 years I was wondering how many other people who have blocked their EGR valves have had Head Gasket or Cylinder head failures.

I know that the EGR valve has the effect of lowering the combustion temperature at high revs and that high temperatures will stress the head gasket and cylinder head possibly causing a failure.

If we can get some figures for people who have blocked EGR and had problems agianst those who have blocked EGR having no problems, and also the number of people who have had gasket/head failures without blocked EGR valves then we may be able to prove if their is any correlation between EGR blocking and higher chance of Gasket/Head failure. This would be useful to people considering the mod or who have carried it out and are concerned of the increased risk.

Hopefully there is no correlation as the Paj certainly seems to benefit from blocking the EGR!

Have a Merry Xmas Very Happy

James

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Crazy dog · *** Joined: 22 Sep 2003 Posts: 127 Location: South Wales

Sorry to hear your news..expensive business as I can cetainly relate to. Had to replace the cylinder head on my last 2.5 Pajero, owing to Balance belt failure which took out the cambelt too.
You don't say if you drive a 2.5 or 2.8, so can you please inform us?

Ian
1994 2.8 Exceed LWB

jimmy · Posted: Fri Dec 24, 2004 13:01 Post subject: EGR a Poll

sorry I have a 2.5, the 2.8 seems to suffer pump failure but is goood on head and gaskets (must be those ceramic inserts!)

James

PoCUK · Posted: Fri Dec 24, 2004 13:58 Post subject:

Hi Jimmy ...

you may be barking up the wrong tree ...

Without a massive response, you could collerate almost anything ... (OK ... hands up, I have a maths degree!).

You could, for example collerate the following :

cylinder head failure with the 2.5 engine (good, as there seems to be a direct colleration) ...

cylinder head failure with recorded miles (also good, as it seems to fail on higher mileage vehicles)

cylinder head failure with sex of owner (looks good, as the majority (not all!) of PJ owners are male, but obviously has nothing to do with it!)

Blocking the EGR valve performs a specific function ... it stops hot exhaust gases from being constantly recirculated back through the engine ... as the engine works most efficiently with cold air input, this can only be a good thing.

I suspect that the need to block the EGR valve is directly related to subsequent cylinder head failure, not the actual blocking of the EGR valve.... ie, there was an original underlying problem that causes the later failure.

Simon

SHED · Posted: Fri Dec 24, 2004 15:48 Post subject:

i had no egr plate and my cylinder head went on a 2.5,under warranty so thankfull for that

Richie · Posted: Fri Dec 24, 2004 16:34 Post subject:

Cylinder head & blanking plate for EGR valve are not related, never have been, newver will be, and never want to be related, just like me and my brothers !!

Nothing to do with the head problem what so ever, and in my opinion, one of the most common failure of head gaskets is: people relying on the temp gauge to much, on the 2.5, it is very very common for the temp gaufge to only go to half, whenit fact, you could make frothy coffee on the steam coming out of the head, and you dont see it.

Heads, best place by far at the moment, Milner, complete full kit availible.

Have fun.

Mork · Posted: Sat Dec 25, 2004 20:04 Post subject:

jimmy

Richie, the EGR valve failing to work can cause the head to crack and/or the head gasket to fail. The exhaust gases being fed back into the combustion chamber have the effect of cooling the combustion temperature significantly, if the engine has been designed to work at these lower temperatures then blocking it off will lead to premature failure. This is usually seen as a burn through in the head gasket near to a hot spot.

For the 2.5 4D56 engine the fact that the cylinder head and block are of different metals also means that if the combustion is hotter and the cooling system weak then the amount of expansion difference the Head Gasket has to deal with is greater again possibly leading to premature failure.

However having done some research in the 4D56 engine it seems that not all are fitted with EGR valves suggesting that they are being fitted to reduce NOx output from the engine (the lower combustion temperature prevents NOx) being produced, and not to keep the head expansion and hot spots within tolerance.

I agree the the cooling system is a likely root cause as the guage does not show reliable temp readings until it is too late Wink