Compression test - Diesel Forum

blksmoke · 06-23-2007, 04:49 PM

My intent is to determine if I have a bad valve from a ticking noise on the passenger side that will not go away. When engine is cold there is no noise, but when she warms up (7.3 IDI) the ticking begins, is constant and increases with rpm's. So, the question is who can help with a compression test? I have a gauge that goes to 300 psi and an adapter that threads into the glow plug hole. First will my gauge work? and second what is the procedure for the compression test? and third what range psi per cylinder is within specifications. I have done compression test on gas vehicles but never on diesel's. Is there much difference? Thanks!

cdnsarguy · 06-23-2007, 05:01 PM

First you need a compression tester capable of well over 500 psi. Some of the cheapazz stores like Harbor frt carry them but not with the adapter included?????? apparently.

If you have a broken valve spring outer or inner it would do that too, mine was outer and did similar.

Greg77 · 06-23-2007, 06:15 PM

Decent compression is betwween 300 and 400. The closer to 400 the better and the more even and consistant the better. I had a 6.9 engine with a tick in it just like yours (rear passenger side). I drove it for 6 or 8 months untill I got a different pickup. When we pulled it it apart the rear piston was cracked. I always thought it would be a valve too but the head was fine.

blksmoke · 06-23-2007, 06:21 PM

What do you think is the best way to locate a broken valve, compression test or removal of valve cover and inspect.If I did take the valve cover off would I be able to see or feel a broken valve and is there a valve in paticular that goes out (intake, exhaust or cylinder # ) What about the adjustment. If they are off will they tick? Thanks!

Greg77 · 06-23-2007, 06:29 PM

It takes less than 5 minutes to pull the valve cover. It may or may not tell you anything but if it's a lifter or such you should be able to see something that's not right. We pulled the valve cover before we pulled the head and didn't find any thing wrong but when we pulled the head we did. Good Luck hope it's not serious.

blksmoke · 06-23-2007, 06:31 PM

Gregg77, Was your ticking audible when the engine was cold after initial start up or did it become noticable after truck warmed up? Was it loud or difficult to hear? Thanks!

Greg77 · 06-23-2007, 06:53 PM

It wasn't real loud but I heard it when it happened and when going down the road you could always hear it. Also when you sped up the engine it became more noticable.

blksmoke · 06-23-2007, 07:19 PM

The ticking in my truck is not real loud. It is difficult to hear while driving allthough when I pull up next to another vehicle or wall/barrier on the road while I am at a stop and engine is at idle I can hear the ticking, and it is much more noticable when the windows are down. The best way to hear the ticking is when truck is at idle, standing outside next to passenger wheel well then it is very noticable, almost like an exhaust leak and after thorough examine no exhaust leak. Well, just waiting for truck to cool down and will remove pasenger valve cover. I will report back with my findings. Thanks again!

Greg77 · 06-23-2007, 07:40 PM

Let the truck run and put your hand over the exhaust. If it is a valve or piston you should feel a puff every so often. I think you can figure it out if you try it, if it stays even and consistant then it may be something else.

wtom24 · 06-23-2007, 07:47 PM

My truck has the same symptom intermittently. It is an exhaust leak near the rear of the passenger side manifold-you can see the stain caused by the leak. It hasn't gotten worse, so i have left it alone, now that I know what it is. Sounds just loke a valve noise.

blksmoke · 06-23-2007, 09:42 PM

OK, I took your advice on letting truck run and putting my hand over the exhaust. Before I started my truck I checked the oil level and it was 1/2 qt low, so I topped her off (I am very good about maintaining clean oil at proper intervals and levels). So then, I fired her up, got her up to operating temp and no ticking noise! I proceded to put my hand over the exhaust (got my hand good, hot and stinky) and what I felt was a nice even flow of exhaust with no puffs or missing of any sorts. Now what? I will drive her until ticking returns then put my hand over exhaust and have another feel! Maybe then cool her down and remove valve cover for visual inspection. What about exhaust leak at manifold? Are they usually intermitent and what type of stain do I look for (everything looks to be a consitant brownish color). What about an injector? If they are bad are they an intermitent tick and would I have any decrease in performance? Or how about the oil being 1/2 qt low. can that be low enough to cause a valve to tick? (as far as I know it never has in the past) You guys are great, giving me some excellent thoughts. Thanks!

cdnsarguy · 06-23-2007, 10:21 PM

The only time I have heard a ticking injector was when it was back feeding compression into the pressure line....... very hot to the touch the line that is. Get a mechanics stethescope or some plastic pipe about 2ft x 1" and listen around the engine to locate it......