No compression after changing head gasket?

Hi,

Is the 25 PSI compression on all cylinders? Are you sure the timing belt/engine timing was installed correctly? If it is out of time, this will happen.

If possible, record it cranking and upload it for me to hear. Also, if the compression is 25 PSI, it won't run.

I attached some important information for the installation of the timing belt. Take a look through them and let me know if this is how you did the repair.

Let me know,

Joe

See pics below.

Yes, 25 PSI on all 4 cylinders. And yes, we did the timing like the pictures say. We followed a Haynes manual for that truck for the specs. I am not anything but a driveway mechanic. It's my son's truck and he overheated it. We could have the timing off. We set it to TDC on 1 with both intake and exhaust Valves all the way "up" so they should have both been open. It's possible we got that wrong.

At first, I thought when he took off the distributor it was off 180. But I checked it, and it was fine. I also have not done a leak down test to see where we are losing compression.

Hi,

When you set to the dead center (TDC), both valves on cylinder one should be the furthest away from being open. Both should be closed. If you have them open, that is the problem.

Also, there is no need for a leak-down test. If they are all at 25 psi, it isn't a leak from a valve leaking, worn rings, or a head gasket. The timing is off.

Let me know if that is what you meant.

Take care,

Joe

At TDC the rocker arms on #1 cylinder were all the way up. If I understood correctly that means the valves are open?

I'm not sure why someone would tell you that. The valves need to be closed when the cylinder is at TDC.

When timing the engine, there are marks on the crankshaft and camshaft that need to align. Take a look at the attached two pics. Pic 1 shows the camshaft and pic 2 shows the crankshaft marks. Check to see if they are aligned. If they are, the timing is correct. If they aren't, that is the likely issue.

Also, look at pic 3 below and let me know which side was all the way up.

Let me know what you find.

Joe

See pics below.

Yes, the timing marks are lined up. On Pic 3 the rocker arm is all the way up. On both the intake and exhaust.

Hi,

If the side that has an arrow on it is all the way up, the valves should be closed, which is what we want. However, if you are one or two teeth off with the timing, they can be in that position but open too early causing low compression.

Unless the head is leaking equally at each cylinder, the compression rings are totally faulty, we have an evenly warped head, or the valves in each cylinder are equally stuck open, timing is the only other thing that makes sense. The aforementioned possibilities are nearly impossible to happen.

Did you remove the timing belt cover to check the timing marks? Can you take a few pics of the timing marks, rocker arms, and valves so I can see what you are dealing with?

Let me know.

Joe

My son overheated it, ruined the head gasket. We had the head machined and clean/tested they said the Valves seat ok. I'm at work so I'll have to get pictures later tonight. We very possibly could be off a tooth or two on the timing. I am hoping he did not ruin the rings.

Yes, I did remove the timing cover, the arrows do line up, as well as the mark on the crank. This is the only picture I have taken so far and saved.

Hi,

Thanks for the update. It's hard for me to tell from that picture. Can you tell me what the white line on the belt is for? Also, the belt doesn't appear to be running true on the cam pulley. Looking at a picture, I can't be 100% sure about that, so let me know.

Joe

The white line is where I had my son make his marks for putting the timing back where it belonged before he took everything apart.

Hi,

Okay, I had a feeling it was something like that. Try to get pics of the marks when they are aligned. I've been wrong before and will be again, but I really feel we are slightly off on the timing.

Take care,

Joe

Update, the timing is off the timing on the crank is off of TDC 1 mark forward. We moved the belt a tooth back and it moves it off 1 mark backwards. The timing belt tensioner pulls is also missing (must have broken) so I believe that the missing spring is not allowing for correct timing.

Hi,

Thanks for the update. The timing was my first suspect. I attached the directions for the installation of the timing belt above. Take a look through them and let me know if it helps.

Take care,

Joe