Low Compression in #8

[gardner]

I have had a rough idle for a while now, also i have replaced most all of the parts relating to this from following all the threads here. I finally had someone do a compression test and #8 was low. All other 7 were around 160 and #8 was at 105. I was looking for an opinion on fixing the one cylinder or since it's apart do the whole head? Or is there something else to check that could be causing low compression in that one cylinder.The car is an 03 w/ 66M miles.

[Merrill]

Understanding that compression has to be contained and that cylinder is not holding it as well as the others it can only be a couple of things. It is getting by the valves because of damage to a valve or valve seat, getting by the piston rings or getting out through the head gasket. Head gasket problems usually show other problems and cooling systems can be tested for combustion gasses to verify a problem there.

[gardner]

i don't think it's head gasket , i've had that before ,but i have had a puff of smoke out the tailpipe on start up on occasion. It seems like i need to tear down that head no matter what , do you think it's possible to just fix one cylinder or just redo that side.

[ctrlraven]

Now that you know compression is bad on #8 you should do a cylinder leak down test.

If you don't know what one is, this explains it.
http://www.youtube.com/watch?v=WgrfT0LFMhc
WgrfT0LFMhc

[ktt]

^^ i agree. A leak down test is needed.. U could be losing compression from int/exh valves. Hopefully its the valves instead of the piston rings. Marauders have a problem with left cylinder head having misfire codes only to find out its the heads.

[Mike M]

It's the valves, it's always the valves on these engines.

[LANDY]

Valve seat is most likely your problem, yes you can get away by doing just one head.

[gardner]

thank you!! It looks like i will have to do the leak down test next.
hopefully it's just the valves. Is it worth doing the coolant mod iv'e seen here once this is fixed. i was curious if that was the cause of the problem in the first place.

[ktt]

left side cyliner head had cooling issues. might wana change timing chain guides/water pump if leaking/cylinder head bolts/tstat etc.. since you will be in there anyway

[Talal DTR MM]

Same what happened with me..see link below.

http://www.mercurymarauder.net/forums/showthread.php?t=76161&highlight=comprssion+test

About month ago. Both heads had been removed, replaced timing chain, water pump but got another issue which is ticking noise ,specially from the driver side & after inspection from many mechanics, it was lash adjuster & i'm planning to replace it this week.

[MMBLUE]

I have had a rough idle for a while now, also i have replaced most all of the parts relating to this from following all the threads here. I finally had someone do a compression test and #8 was low. All other 7 were around 160 and #8 was at 105. I was looking for an opinion on fixing the one cylinder or since it's apart do the whole head? Or is there something else to check that could be causing low compression in that one cylinder.The car is an 03 w/ 66M miles.

Same thing happened to me. For me it was just cheaper to replace the whole engine.

[babbage]

Is it worth doing the coolant mod iv'e seen here once this is fixed. i was curious if that was the cause of the problem in the first place.


Yep. Get a rear head cooling mod on there or it will happen again.

[mtenderenda]

I had the same problem. Found out, before my power train warranty expired that its the cylinder head. The head would warp from heat. It was considered a defect. I brought it over to my closest Ford Dealer, explained to them exactly what is going on and what tests was performed and the results. They agreed to replace the head, under the power train warranty..

[gardner]

how long was the power train warranty for the 03 marauder?

[ctrlraven]

how long was the power train warranty for the 03 marauder?
3yrs/36k miles from the original sale date when it was first sold brand new. If you had an extended warranty from Ford it would be for whatever you warranty length and mileage you decided on.