2.5td Compression

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DougLang

Active Member
Posts
131
What sort of compression pressure should I expect from a 2.5td. What would be the minimum before rebuild? Throwing oil into air filter, hard start and rubbish up hill. Pessures please if anyone knows them. Thanks
 
As said in the other thread:

500PSI? That would be a compression ratio of about 34:1.

The compression on these engines is 308.7PSI, as its a 21:1 compression ratio on the 12J and 19J engine.

While I am at it, the 200tdi & 300tdi engine is 286.65PSI as its 19.5:1.
 
As I said on the other thread this seems very low as good. Is 300 really a good pressure or a pressure for a rebuild. I would expect 500!
 
I am told by you guys that 300psi is the compression pressure for a 2.5td. Mine has oil ****ing out into the air filter and has massive of gases at rocker cover and dipstick. So I tested it. It returned 18bar (261psi). I then added 5ml of oil to bores and it then returned 22bar (319psi). How can it be higher than new with 5ml of oil. The oil should improve it if it is the rings but make it better than new? Also... is 261 really bad for this engine. To rebuild or not... that is the question. I am in your hands..... 200tdi or not!
 
A new engine doesn't have the advantage of a 'perfect' seal. Liquids are incompressible, so by adding the oil, and slightly subtracting the oil's drainage through the piston ring gaps, you have 'perfect' compression.

In other words, take a new engine with the piston rings left out, use a thick enough shot of oil per cylinder, and you get 300psi.

Your shots of oil just make up for the wear.

Having said all that, I'd bet that new 2.5 engines fell short of 300psi.

Perhaps look for other causes for positive pressure? Worn valve guides/seals?
 
As said in the other thread:

500PSI? That would be a compression ratio of about 34:1.

The compression on these engines is 308.7PSI, as its a 21:1 compression ratio on the 12J and 19J engine.

While I am at it, the 200tdi & 300tdi engine is 286.65PSI as its 19.5:1.
Hi all,
I am no mechanic. It seems that the 19j biggest issue is the pistons and piston rings. Is there no way of boring out the cylinders and buying new stronger pistons and rings? Surely this would fix the problem and if you could adapt the 200tdi's intercooler to fit, this will keep temperatures lower limiting the chances of cylinder block cracking?
Then maybe you would get some of the reliability back on a otherwise strong engine. As I say I'm no mechanic and as I have a 19j that has either popped a ring or the timing belt has slipped, I'm looking at a longer term fix.
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As I say I'm no mechanic and as I have a 19j that has either popped a ring or the timing belt has slipped, I'm looking at a longer term fix.

Fit a 200/300TDI.

Boring out would weaken the block, these engines were tough as nails in the NA form, but all the additional stresses from the turbocharging cause issues, the head cracked too, the block had to be beefed up a bit and even then it could let go.
 
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