Power loss when warm, overheating

[Trucky McTruckface]

There are a lot of little issues here, some unrelated but bear with me. I have a 1981 Rabbit Pickup 1.6 IDI that I picked up about 4 or 5 months ago. I rebuilt the shift linkage, and changed all the filters and oil with some other non-engine related odds and ends. The truck since I've had it has run great and immediately starts up but the temp gauge has not read right. It didn't pay it much mind since the truck was running great. I've been taking it on longer trips. sometimes an hour or two with highway driving with good performance.

A few days ago on the highway I noticed the car seemed to "miss" and loose power which got progressively worse. I made it home ok and checked around but didn't notice any leaking but did notice that it was low on oil. I topped it off and the next day it ran great again on a little trip in town. Yesterday I tried to take it on a longer trip and it started and ran great for about 20 minutes. Then I started to notice the lack of power again. It got worse and worse until I could barely go 15 mph and pulled over. I check around to see if anything was wrong but I didn't notice anything. I didn't notice any smoke from the exhaust at the time and there was enough oil (although less than before). I got back in a restarted and it started right up and ran great again for a few minutes until the same thing happened. I was almost home now and I was at a light. When I shifted into first and pressed on the gas I heard a thud and then my engine noise became VERY loud with lots of vibrations but seemed to have more power. I made it home and it sounded like the coolant was boiling and I noticed some coolant around the reservoir tank which must have leaked out. Oil level again lower but acceptable. I didn't have any more time to look at it so I had to leave it for the next day

Today I changed the coolant temp sensor and drove the car. Again at the start when cold the car starts and runs great although the exhaust is still loud with lots more vibrations. Sure enough after driving and warming it up to about the halfway mark the car starts to stutter and loose power on harder acceleration. I let it idle in the driveway and noticed that the radiator fan does not come on until the temp is almost in the red. While it was warm I revved the engine a bit and then notice a lot of whitish maybe bluish smoke coming out. The coolant level does not seems to change

At this point I know it burns a lot of oil (maybe from worn rings) and it seems like I have a bad head gasket and/or warped head (possible from overheating from a bad fan switch). But what I don't get is the whole thud and vibrations and engine noise? What caused that? Did I have an exhaust blockage? Maybe it's unrelated? I'm assuming a compression test is next but just want to know if anyone else has ideas.

[TylerDurden]

Might be more than one issue here...

I would:

• Check the crank sprocket: if you can loosen the crank bolt with less than a major breaker bar, you may have trouble with a damaged key/keyway.
  Replace the crank sprocket if needed, certainly the timing belt.
  Re time the engine (crank/cam/IP).
  Run a compression test.
  Check for emission vapors in the coolant.

[Trucky McTruckface]

I put a socket on the crank pulley center bolt and went back and forth on it. I was able to rotate the engine and transmission and actually move the car (it was in gear). Seems to be ok. Thank you for the tip.

I definitely think that there are exhaust gases in the coolant since it is probably seeping out of the top from pressure and I think I notice condensation. I'm almost positive I have to do the head gasket and a new timing belt will come with that. Also I will replace the radiator fan switch. My real fear is the block and piston rings. I really don't want to be in for a full rebuild. The vibrations are what worries me since I really can't figure it out and I'm hoping it not from some internals. I checked my motor mounts but the seem ok although I really don't know if I would be able to tell if they were bad. They are not obviously broken. I have a broken rubber exhaust hanger but holding pressure up against the exhaust with some rags didn't seem to change the vibrations.

I suppose the one thing it has going for it is that the truck starts and runs beautifully with out any hiccups every single time even now when cold. Problems are only when it heats up. The vibrations are always there though. Hot or cold. Are there any common causes of bad vibrations on these trucks?

[Trumper]

What you have described in the first post is exactly what I had in an engine (many years ago) when I had one of the combustion pre-chambers partially drop out into the cylinder and then get beat back into the head with the piston rotation. Exactly.

The head got to temp and then the pre-chamber fell down......bang. Then, everything seemed better when it got beat back into the space where it is supposed to be. I drove it 70 miles because I HAD to get down to the farm to check on my elderly parents and feed the cows. I lost a lot of power in the last 25 miles and ran a little hot.

By that time, all I wanted to do was make it to my destination because I had several more of these cars there. I kept driving it. I shut it off and walked away. Couple of days later, I returned and tried to start it. I would not start. I kept trying. It eventually started and then totally dropped the pre-chamber and it was game over.

With autopsy of the engine, it was CLEAR the pre-chamber had been moving back and forth and beating the head and piston to oblivion. Eventually, it jumped ship and turned mostly sideways in the bore. Only engine I EVER destroyed. They were rather plentiful back then. Times have changed.

[Fatmobile]

Get clear fuel lines.
I'm almost certain you have a a fuel line restriction that will show itself as air in the fuel lines.

[Trucky McTruckface]

I am in the process of taking off the head to inspect it then doing the head gasket and the motor mounts. On inspection of my mounts they were pretty much all destroyed and I think the last klunk was one of them breaking. I have the engine mostly apart with the special injector pump and camshaft locking tools in place. I am also going to replace air conditioner components while I am here so most of that is out as well.

The Bentley manual does not really go into detail at this point about removing the head. I have loosened the injector unions to the injector pump hard lines but it seems I have to take out the lines completely or move the pump to get them away from the injectors. Any tips on this?

Also, the intake and exhaust manifolds are still connected to the head. I have read a few places that people leave these on and take the head out as one whole unit with the manifolds on but I think is rather try to get them off. The Bentley manual says to undo both the exhaust manifold and the connector pipe to the rest of the exhaust. Would I be able to just take the exhaust manifold off of the head and leave it on the rest of the exhaust?

And last question. To get to the passenger side motor mount it looks like I have to take off the sprocket on the injector pump. If I remove the nut with the special tool in place and then take off the pulley, take off the bracket, and replace the pulley and special tool will this keep the timing or will it have to be reset?

[TylerDurden]

If the passenger mount is shot, you'll have to pull the IP and lines. Not much work there.

The manifolds' are a bit awkward to get to, but I think they can be disconnected in place. (The intake probably needs to come out.)


Any time you slack the belt or pull the pump, you want to reset/check the timing.

[Trucky McTruckface]

I suppose I should be a little more specific. To get the head off, how to i remove the injectors? Do I disconnect the hard lines to the injectors AND the pump (both ends) or do I move the pump out of the way.

I did manage to get the intake manifold off from underneath the car and will do the same for the exhaust manifold but want to know if I can leave the exhaust intact (unbolted from the head but manifold still connected to the rest of the exhaust) or do I have to disconnect the manifold completely? The manual says to disconnect the manifold from the rest of the exhaust but i can't for the life of me see why and I'd rather just leave it there intact.

[TylerDurden]

I undo the lines at both ends while they are all fastened together in their looms. The important part is making sure the bubble flares are seated properly when re-installing.

If you can get the exhaust mani off/on the head without popping it off the toilet bowl, I say go for it.

[Trucky McTruckface]

Re-read the post saw you answered the question. Yes I see the injection pump has to be moved to get that bracket. It seems that if I wanted to do something like a compression test I could get away with just removing the hard lines at both ends.


Also I unbolted the exhaust manifold from the head and left it on the exhaust. I placed a support under the exhaust to support the weight of the manifold. I assume that would be the only reason to disconnect it completely.

[Fatmobile]

Put some caps on the injectors and pump fitting so dirt doesn't get in them once you remove the lines.

There are different kinds of exhaust downpipes. The toilet bowl will let you swivel the exhaust away from the head so it won't be in the way when you go to put it back on. the 4 into 2 into 1 pipe not so much.

Most of the reason for removing the intake and exhaust, other than it being very heavy and hard to remove for one person, is because if you use studs to line the head up when putting the head back on; it can be hard to lift the head over them without hitting the rain tray with the intake.

Don't use the "upside down man" motor mount on the p-side. Get the good strong inverted V type.

[Trucky McTruckface]

I noticed the edges of the intermediate shaft pulley are damaged. Someone probably did it with a gear puller doing the water pump in the past I would guess. I've read that these had smooth edges on later models (not raised on the edges to keep a belt aligned). Two questions. I'm assuming I can just pull the gear and the intermediate shaft isn't "timed" since it has no teeth and the Bently manual only talks about setting the crankshaft, camshaft, and injector pump. Also, can i grind down the edges of the intermediate shaft pulley?

[Trumper]

Correct, no timing on int. shaft.

I have removed the sharp edges on all of my int. gears for over 20 years. I use a small hammer (with the pulley on a soft wood block for cushion) to remove the edge. Then, use a round file and a flat file to smoothen the surface. A grinder is fine if not over done.

Just determine if the pulley is bent prior to removal and be careful removing it from the shaft. Gentle hands do good work.

[Trucky McTruckface]

Thank you. I am going to work on that today.

I read in the Bentley manual that they recommend knocking out the pre-chamber insert to clean the head. It doesn't mention how to get them back in however. Do they need to be pressed in by machine? What holds them in? Trumper's story about the fallen pre-chamber has me a little nervous about messing with them. This is my first diesel and they don't have these things on gassers!

[Trumper]

I NEVER remove them. Other people will say different things. They are simply held in by interference fit.

The only time I would remove one is to replace a cracked one and I would employ an oven to heat the head prior to that procedure. If done that way, the valves and springs would have to be in the head to keep the valve seats in place. Obviously, the stem seals would have to be replaced after the procedure. You would have to measure and compare the height of the pre-cup and machine the top of the pre-chamber (to be inserted) to ensure fit/depth once inserted into the head.

I personally hand sand the face of heads using a precision ground block (flat) and various grades of sand paper. I use a straight edge to carefully determine flatness in multiple readings (places) on the face.

You will get differing opinions as some are reckless (quite frankly). You will be told the cups can be unceremoniously knocked out with a punch and hammer......no thanks.