Replacing head gaskets, what else?

[Big Bart]

As you mention you need a diesel compression tester. If your glow plug compression tester fitting is the same as the leak down tester you can use that on your glow plug fitting. Harbor Freight has a cheapy (Have to cut off the bottom part of the glow plug adapter as I recall.) Or buy a OTC one for something that will last. Or find a used Snap On off CL, Offer Up, or Ebay.

Ford did not document what proper compression limits should be, they just stated no two cylinders should be more than 20% differnent. I was teasing another member the other day that even though he had zero compression across the board, according to Ford he was good to go!

But for your reference many of us get 400-430psi on compression stroke 5 or 6 with a lower miliage engine. (Under 200K) Some are in the 300's doing the same test but their trucks run good. But if you are in the 200's you should be thinking rebuild VS just heads. Unless your heads are the issue.

The leak down test is basically sending compressed air down each cylinder while it is at TDC in the compression stroke. (That means both valves are closed.) The tester will show how much difference between the air pressure you sending out and what the cylinder holds. In your case you will take off the oil fill cap and listen. You may hear a little air and that is ok. (Some air is likely to get past the rings.) But if you compression test said 225psi on cylinder 5, you can hear and feel air pouring out the oil cap. Well you know your rings or piston are shot and need to be addressed. (No use doing heads, to have to pull the motor in 5,000-15,000miles for rings.

In a normal leak down test you would also listen at the intake manifold opening and tail pipe to determine if either valve is leaking. In your case you are doing a valve job so not needed in this example.

Also you will need to hold the engine at TDC for each piston. (The air is going to push the piston down.) So use a wrench or socket on the damper nut. Also start at say 50psi and go up to 100 PSI if your system will allow VS starting at 100psi and the crank trying to turn. If you are losing more than 25% of the PSI going in and you hear and feel a lot of blow by coming out of the oil fill port, then you should think about doing rings and bearings at a minimum.

Also its probably 50/50 if the valves and piston collided you will need to replace the piston. (Send pics, collectively we can tell you what is the best course of action.) If pulling one piston you would simply replace all the pistons, rings, and bearings. Probably at least have the cylinders honed or bored, cam bearings replaced, if needed decked, and crank checked.

But then you have a long term runner!

 

[RSchanz]

Ok so I performed my compression test yesterday. The needle would peak around these numbers but the pressure wouldn't remain in the tester. I'm assuming that it just doesn't have a check valve but I was watching the gauge while someone turned the key. Does it matter if there isn't a check valve? Numbers are as follows (6 strokes on each cylinder):

Pass side front to back:
1:300
3:300
5:250~
7:300

Drivers side front to back:
2:300
4:300
6:280-300
8:300

300 more or less all around... not bad? Not great? Thoughts? 5 and 6 both being slightly lower seems interesting since they are opposite of each other. Could this be because the head gasket is leaking in those rear corners? I would have thought the back two cylinders (7,8) would have been the worst because of their location to the rear leaks. Btw, the leaks are pretty solidly plugged now after using bluedevil . Upon removing the plugs I did find that autolite were in it , ordering Beru replacements.

Coolant still seems to be mysteriously disappearing and pressure remains under the cap for days without running it. There are no signs of coolant oil/mix and I wouldn't describe any excessive smoke either. I warmed the engine before the test and when I took the air filter off there was smoke coming from there. Does anyone know if this is abnormal?

I still need to perform a leakdown test, so I'll report back after that. Thanks to @Selahdoor for helping instruct me on how to rig up an HF compression test kit that fits without needing to modify anything besides the gauge.

 

[IDIBRONCO]

I warmed the engine before the test and when I took the air filter off there was smoke coming from there. Does anyone know if this is abnormal?

This isn't smoke. This is (I believe) just crankcase gasses coming through the CDR into the intake. Perfectly normal for our engines.

 

[RSchanz]

This isn't smoke. This is (I believe) just crankcase gasses coming through the CDR into the intake. Perfectly normal for our engines.

I believe you’re correct. Smoke wasn’t really the correct term. You save me every time, any input on the compression numbers? Think the fact that there isn’t a check valve means I’ve gotten an inaccurate reading because of a leak somehow?

 

[IDIBRONCO]

any input on the compression numbers? Think the fact that there isn’t a check valve means I’ve gotten an inaccurate reading because of a leak somehow?

Here's my thoughts on the compression numbers. They all seem to be getting toward the low end-BUT... First of all, don't worry a lot about that. I say that because, other than #5, they are all pretty even (I'm not sure why #6 has a varying compression reading and that just makes me say HMMMM). Remember that this engine is probably original to the truck so it has a lot of years and miles on it. Are they terrible? No I don't think so. The "lower" numbers could be due to valves that aren't perfectly (read as less than 100%) sealing or just, plain valve wear. I don't think that the lack of a check valve in itself would cause inaccurate readings, but it may (slight chance) be part of the reason for the lower readings. Maybe, instead of 6 strokes, you should try the compression test on all cylinders with 10 strokes (to throw out a number). The lack of a check valve MAY (again a slim chance) cause the compression readings to rise slower than they would with a check valve in the tester. See what another test with more compression strokes does to the readings (possibly nothing). Then do a "wet" compression test. Dump an ounce or so of oil into the cylinders. That will help to seal up the rings and may give you different compression numbers. Be sure to turn the engine over several times with the starter before putting the glow plugs back in just to try to clear out as much of the oil as possible. Post those results and the results of the leak down test for us to see and ponder over please.
Now for a different subject. I understand that the external head gasket leaks are stopped right now, but don't assume that it's in any way permanent. No amount of "Mechanic in a Can" will fix an actual mechanical problem. It may buy you some extra time, but still plan to replace your head gaskets. That will also give you the opportunity to visually inspect your heads/valves (and maybe have them repaired). Of course if a leak down test shows that you have leaking valves, then you know that the only way to fix them is to remove the heads.
These are my opinions and suggestions. Others may have different ones so don't take mine as gospel.

 

[RSchanz]

I'm fairly inclined to just get a different tester. Harbor freight has a new edition that I think is legit and shouldn't require any fiddling with adapters. Either way, I do feel like I should try the test again although I'm going to do it cold this time because a couple of the GP's are a PITA under the hard lines. I'm assuming obviously 1 qt split evenly amongst all of the cylinders? Will the oil in the cylinders affect the leak down test? Should I do the leakdown before I do the oil in the cylinders? Is there a tech 101 on leak down tests?

I totally agree with you on the temp. fix of the stop leak. The goal for me is to determine if I should pull and rebuild the entire engine/if any of this work is worth it based on the quality of the engine.

 

[IDIBRONCO]

Should I do the leakdown before I do the oil in the cylinders?

Yes. That would be the best way to go. Since the oil helps the rings to seal, it may affect the results of the leak down test is the rings aren't sealing well. I don't think that you'd need 4 oz. of oil per cylinder. If you do use that much, be sure to do a lot of turning the engine over without glow plugs to blow most of that oil back out. You may even want to let the engine sit for a few days to let the oil run out between the ring end gaps. I think that trying to start the engine with that much oil in the cylinders would hydro lock the engine. That would also probably bend a rod if there was very much piston speed before the hydrolock. That's why I only recommended using about 1 oz. of oil per cylinder. The different compression tester wouldn't hurt either. Of course, with a different tester, you would want to start at the beginning again. Do the dry compression test and record your numbers. I don't think that you'd have to run the engine to get it warm again if you do both the wet and dry tests. The reason for doing this is consistency. Different testers can give different results and they can vary by quite a bit some times. Which set of numbers is right isn't quite as important as consistency at this point. You are trying to determine the cause of the one low cylinder without dismantling any more than you have to. That is why consistency is most important at this stage. If you suddenly have all cylinders reading at 330 with a different tester, now you have different readings plus you don't really know why one cylinder was reading lower with the first test. Was it the gauge? Was it the operator? Was it something completely unexplained like the threads on the adapter just didn't like to seal as well with that one cylinder?

 

[RSchanz]

Sry, read 1qt when you said 1 oz. Will take everything you said into account and report back. I'll be out of town for 4 days starting tomorrow. I'll sprinkle work in here and there afterwards.

 

[Big Bart]

My two cents on your compression test -

That is the lower side of compression and yes your compression will increase if you have a schrader valve in the gauge. It will build up each stroke and likely improve by 25-75 PSI per cylinder. So I would try to get a new HF guage, but open the box before you buy it or in the parking lot.(So you can quickly return it.) You should see a valve (Like on a car tire or bike tire) in the end of the hose that hooks to the guage. It should also have a release button on the side of the fitting for the connection or up on the bottom of the guage.

Ford never posted what is good compression. Rather said no two cylinders should be more than 20% different. So as a guage, I have about 430PSI accross the board. Newer engines will likely be at 450-470psi. But I would not have an issue if mine was 300 psi but running stong. So in your case the 250psi is still more than 80% of the 300psi, so by Ford spec it is ok. The issue is your test is not with 5 compression strokes, its just one stroke, tested 5 different times. Think of a ballon, if you blow in and let it come out, it will not fill up. Blow into a balloon 5 times it will get bigger with each breath.

So the 250psi could stay 250psi and the 300's could go up to 325 or 350psi. (So not out of spec.) Or they all could go up. You will not know till you get a better compression tester. But clearly the cylinder that is 250 has something diminished. Rebuild at this point? Well that is a call we all of us have to make. Can we live with 7.5 cylinders as a Home Depot and dump runner, or do you tow 10,000lbs daily for a living and need something that is reliable.

So there are things you have to look at before running a diminished engine, you don't want to destroy it, that way you can rebuild it later. Do you have excessive blow by pumping oil into the intake manifold which can cause more damage. (A little is ok/normal. A working CDR valve will manage light blow by.) Do you have coolant leaking into the oil because of a head gasket. Is the cylinder dead above idle and now just leaks diesel into your oil, is diluting it, and thus will damage the engine. These engines are known for running fine on lower compression and to some extent weak cylinders. So if you do not have a head gasket issue or extreme blow by you should be able to run it as is till you feel a need. (Engine issues or lack of power.)

 

[Big Bart]

My two cents on the coolant/pressure issue.

This one is a little concerning.

1) I would start with a new radiator cap to just take that out of the equation, they are cheap. Get the one with the red tab on top, so you can release pressure and remove when hot. VS turning it loose and hoping it does not spray hot coolant on you.

2) I would borrow, rent one (Auto parts store.), or buy a radiator test kit. Then hook up to the radiator. Start the engine and see how the pressure builds up from cold to warm. If you see the pressure fluctuating (Like with each compression stroke of single cylinder.) or building rapidly you likely have a head gasket issue or a crack in the head or block. Do not let the pressure go above 13psi, most pressure testers allow you to pull the cap to the side and the pressure releases. But you may have to twist and lift like a radiator cap, if so use a cold wet towel and glove to prevent getting a burn.

3) If it slowly builds up to 13 PSI that would be normal, but if it builds up in 60-120 seconds there is a compression stroke leak into the coolant system. You may have to put the new cap on, drive and test. Repeat 4-5 times to see if you can catch it building rapid pressure. Maybe try accelerating the engine to see if at higher rpms (Higher compression.) you see something fluctuate.

4) Maybe the stop leak has fixed the issue for now, so maybe you will not have an issue or see an issue.

5) Your radiator cap is supposed to seal the system and hold at 13psi. So if your radiator is say 3-5 inches low on coolant, perhaps at 13PSI when you shut it off. Even when things cool down your radiator could still be holding 5-10 PSI. That would not be unexpected or un-normal. But I would not expect it to hold 13psi after things cool down and contract.

Let us know what you find.

 

[RSchanz]

Ford never posted what is good compression. Rather said no two cylinders should be more than 20% different. So as a guage, I have about 430PSI accross the board. Newer engines will likely be at 450-470psi. But I would not have an issue if mine was 300 psi but running stong. So in your case the 250psi is still more than 80% of the 300psi, so by Ford spec it is ok. The issue is your test is not with 5 compression strokes, its just one stroke, tested 5 different times. Think of a ballon, if you blow in and let it come out, it will not fill up. Blow into a balloon 5 times it will get bigger with each breath.

This makes total sense and I didn't think about it like that before. I returned that kit and bought the newer kit that should work well. BTW- if you tell HF that the gauge isn't working or just the kit isn't working in general you shouldn't need to pay the restocking fee.

My two cents on the coolant/pressure issue.

This one is a little concerning.

1) I would start with a new radiator cap to just take that out of the equation, they are cheap. Get the one with the red tab on top, so you can release pressure and remove when hot. VS turning it loose and hoping it does not spray hot coolant on you.

I've tried 16lb caps, 10 lb caps and even 7 lb caps. Nothing really seemed to help. The rad is a new champion rad. I forget which cap is on now but I think I will go back to the 7lb for a little.

2) I would borrow, rent one (Auto parts store.), or buy a radiator test kit. Then hook up to the radiator. Start the engine and see how the pressure builds up from cold to warm. If you see the pressure fluctuating (Like with each compression stroke of single cylinder.) or building rapidly you likely have a head gasket issue or a crack in the head or block. Do not let the pressure go above 13psi, most pressure testers allow you to pull the cap to the side and the pressure releases. But you may have to twist and lift like a radiator cap, if so use a cold wet towel and glove to prevent getting a burn.

I didn't realize you could turn the truck on with it hooked up. That makes sense though... so instead of pumping it to add pressure I just put it on fire up the truck and watch it build on its own? I don't think it's low because it still squirts out when I loosen the cap.

 

[Big Bart]

Be careful as these trucks are aging, running a 16lb cap can push a part over the edge and create a leak. Head gasket, radiator, water pump, heater core, hose, etc.

You pump up pressure to find a coolant leak. Push it out the crack or hole. But that can be problematic if looking for a headgasket or cylinder head leak. (Hydrolock a cylinder and bend a rod if you do not pull the glow plugs.)

You can run the engine with a tester to see if you have rapid build up from a head gasket or cracked head. Just release pressure if you get above 13psi. As I recall on mine if I tilt the hose or cap it released the pressure.

The only time a idi would build pressure rapidly is if you had a head gasket leak to the cylinder or a cracked head. But you would know a severe leak (Gasket is blown out.) if you took the radiator cap off and ran it. You would see lots of bubbles and air. A small leak you would more easily detect with the radiator tester.

 

[RSchanz]

Alright! I'm happy to report that the new HF tester works great. As luck will have it by at least the last cylinder I realized I had nudged the IP wire back on and the IP started working again. I could see the diesel spewing out when I performed the test. Now, my question is... what does this mean? Does this mean the number for the last one is not accurate? I honestly think it may have happened on the last two because I thought it kind of smelled like diesel but figured maybe it was a nearby truck idling or something. Anyways, numbers are as follows and much stronger but kind of all over the place. Whats up with cylinder 3??

Pass side front to back:
1:440
3:485
5:400
7:460

Drivers side front to back:
2:400
4:410
6:410
8:435

I still need to perform a "wet" test and leak down.

Thanks

 

[chillman88]

Alright! I'm happy to report that the new HF tester works great.

Does the new version work without modifications? I've been thinking about picking one up myself.

 

[Big Bart]

Some thoughts on you varied compressions -

Did you only do 5 compression strokes on each test? To get the right results you have to use the same test criteria. So it could be 5, 6, or 7 but it has to be the same amount for each cylinder tested. It can go up each stroke.

Did you put a charger on the battery? It helps the accuracy if the starter rpm is consistent.

Keep in mind this is a harbor Frieght guage. So don’t expect it to read perfect.

Also if you partially filled the cup chamber with diesel, it would raise the compression.

Also did you either have all but that cylinder’s glow plugs in or out. My point is if after each cylinder test you left out that plug, well you first test had 7 compression strokes in between that cylinders compression stroke, your last one only had itself. So the starter would have turned the engine faster raising compression after each cylinder you tested.

Bottom line is you do not have a dead cylinder, you seem to have good compression. Now do a leak down test just see if any one cylinder has more blow by into the crankcase and out the oil fill hole. But from the looks of it you can just do the heads as your bottom end seems to be making good compression. Now if there is something visual with the heads off like a scorn cylinder let us know.