Citroen C5 MK3 THP 1.6 Compression Testing

[Brian C5]

Update. Took rocker cover off and checked cam timing and it was spot on!!!!

Anyone got any ideas ?????

[wheeler]

Do you have a figure of what the compression should be on this engine?
Are you holding the throttle fully opened during the test?
Did you put a couple of squirts of oil down the bores first?

[Brian C5]

No I don't have any figures for this engine was hoping could get some via this forum.

Yes I did keep the throttle fully open whilst doing the test.

I only did dry tests.

Tomorrow I am going to remove inlet manifiold and inspect the valves for carbon build as this engine is very prone to this. If they as ok I will get the coolant checked for exhaust gases to make sure there is nothing wrong with the head gasket.

Thanks for the suggestions much appreciated.

[xantia_v6]

Are you sure that your new compression tester is sealing properly in the spark plug holes? It seems strange that you started with a problem on one cylinder and now you seem to have a problem with 4.

Did you run the engine before doing the compression test? If not, maybe the hydraulic tappets were not full of oil.

[Brian C5]

I find it very strange too. My old Laguna that's covered 132K was given readings around 130 PSI so I thnk the new compression gauge is ok. I did make sure everythhing was sealed whilst doing the test. I have taken off the inlet manifold off and examined the condition of the inlet valves. The valves are badly covered in carbon (the joys of direct injection) and I am in the process of cleaning them with egr cleaner and lots of different brushes and rags etc.. Not sure if this is the problem but the job requires doing anyway. After the long process of cleaning is finished I will try start the car and see what happens.. I will update you on what the outcome is.

Thanks again for your help.

[Brian C5]

Car was put back together and it fired on all cylinders but was running too rich. Cleaned the MAF sensor and this made a big differnce. Took it a run today and it is running very well and the mpg has improved greatly. Hope it stays this way as it is early days yet! Thanks for all your help and advice.

[xantia_v6]

Which version of the engine do you have? I have been assuming it is turbocharged 156HP, and they don't have MAF sensors. They do have a MAP sensors either side of the throttle.

[Brian C5]

It was a keyboard error it is a MAP sensor on the 156 THP I cleaned. Car has now covered a 100 miles since cleaning valves and sensor and it's running like a new car. Acceleration and MPG has greatly improved and if it stays like this I will be a happy man. Thanks again for all your help.

[xantia_v6]

Thanks for clearing that up. Did you clean the sensor on the boost pipe, or the one on the manifold?

[Brian C5]

I did both as I had good access with all the pipework removed. I noticed the sensor on the manifold had an oily film inside not sure if that was causinging any problems but I cleaned it out anyway. Cannot believe in the change in the car it is running and performing like a dream. I wouls recommend anyone with this engine to clean the inlet valves no more than 40K. It's a pain but it really makes a big difference. I looked into walnut blasting but in the end decided to clean them chemically myself. I remember "Car Mechanics " did it this way on a project Peugeot 207cc fitted with the same engine. Hopes this saga/outcome helps someone else.

[gwest]

Brian that is a really useful bit of information to have on the forum. And I suspect some understatement of the pain fullness of the procedure! Any tips on the most useful scrapers and solvents would be useful- I did have some success recently on a dismantled N13B16 cylinder head cleaning the combustion chambers with kerosene followed by acetone using a bristle brush.

[Brian C5]

I cleaned the valves with EGR cleaner (purchased from Europarts) and used a number of coathanger wires sharpened at the end and bent at different angles to get behind the valve stems. I also used a long thin screwdriver and filed a U shape on the end of the blade to help scrape the valve stem. You will also need lots of rags.
To ensure I didn't get any chemicals into the combustion area I removed the rocker cover and turned the engine over to position the camshaft lobs in the upwards upwards position (firing stroke) for each cylinder being worked on. You also need a torch and mirror to see the valves that you are cleaning.
It takes time to do them properly but it is worth it and it is a safe method to clean them. I was worried that walnut dust could get into the combustion chamber and cause more problems. I was getting quoted £400 for walnut blasting but I did it myself for about £10 . Hope this helps anyone with the same problem.

[MattBLancs]

Couldn't you (using a long spanner) turn the engine over manually?

You need to turn the engine quite a bit faster than you could by hand to build up decent compression.

To confirm, as tried various methods to complete a compression test on an engine on a stand (starter mounts to gearbox, engine on stand mounted via bellhousing bolt positions, so not able to rig up a starter)

Turning engine (socket on crank pulley bolt and)

• with a speed brace, easy to go fast enough until you reach compression stroke on the cylinder with the compression tester plugged in, grind to a halt and can't build compression quickly enough

• with a breaker bar and socket, easily overcome compression, but can't go fast enough

• with an SDS drill, chuck, hex to half inch drive adapter and socket. Insufficient torque to turn engine over, even without any plugs in. Torque limiter clutch on drill cuts the drive.

• 18v Makita drill driver, socket adapter and socket. Able to drive engine round without any plugs in, but can't overcome compression with tester plugged in. Very hard work for drill, gets hot!

Breaker bar was nearest to success, but compression values achieved all over the place, no consistency at all - repeating test of same cylinder giving different results.
Gave up as a pointless endeavour!

Glad to read on later in this thread that it seems to be fixed