Hello all,

ENGINE: 1977 Dodge 6.6L/400 Big Block, with standard external oil pump

VEHICLE: 1977 Dodge, W300, 400/6.6L, 2-bbl, 4-spd manual, 4x4, 1-ton, ex-fire truck (brush truck)

CONDITION: The engine has about 35,000 original miles on it.

PROBLEM: Sudden complete oil pressure loss and extreme valve train noise.

BACK STORY: The tuck ran great for about two months and then one day just suddenly lost oil pressure while sitting at an idle (no-load) at a stoplight. The oil pressure gauge bottomed out and the valves instantly began rattling terribly. The temp gauge read normal range, it was full of oil, there were no strange happenings prior to that, just normal driving around town. It was about 40 degrees outside that day.

I immediately stopped in a parking lot. I attempted to replace the oil pump with a high-volume pump but could not because that truck frame has a clearance issue; I would have to grind the pressure relief valve hole in the frame to enlarge it. I did clean and inspect the original pump, change the oil and filter, and the problem disappeared. I had good oil pressure again and no other issues for two weeks.

But then it happened again. This time the oil pump was replaced; standard volume pump. The the oil and filter were also changed and the problem was solved again, for about two weeks (again). We have been using Valvoline (dino) 10W40, Marvel Mystery Oil, and Carquest filters.

It happened again yesterday (3 times now). Unfortunately, this time an oil and filter change did not resolve the problem. I dropped the pan and this engine is CLEAN! There was no metal, no metal flake, no sludge, and no dirt of any kind in that pan...

Seriously, I could have wiped the oil pan out with a paper towel, poured some Campbell's soup in it, and ate my lunch right out of it. I don't get it...

The pickup tube looked new. The screen was bright silver and clean. There were no cracks in the tube, it was securely fastened into the block (screw in type tube), and I could not find any reason for oil not to be getting to the pump.

I removed the new pump and blew a whole can of carb cleaner through the pickup tube, from the intake port in the oil pump back down through the tube. After about two seconds, the solvent was coming out clear/clean. I blew cleaner through the oil pump output (pressure) port and into the engine. The cleaner dripped out from the #1 main bearing. Nothing seems to be blocked in the engine. WTH???

The only other consideration (incident) I know of was the owner once started this truck when it was about -10 degrees out and gave it about half-throttle right away to "keep it running". He did it in front of me and I chewed his *** immediately about revving a cold engine. I am wondering about a spun bearing because of that. BUT, there was NO material in that oil pan, I did not see a spun bearing when I had the pan off, and the issue has been intermittent. I would think a spun bearing would have spun and caused this oil pressure problem right from the get-go; and would have blown the engine by now...

What could be causing a basically new engine to suddenly lose oil pressure like this? Are the new style oil filters designed incorrectly for this old engine given that they are mounted horizontally on this engine instead of vertical? I keep thinking air is somehow cavitating the oil pump because of the horizontal filter. Am I crazy?

ANY ideas??? I will appreciate any ideas not listed above folks!

Thanks, -C.R.

 

You may have already checked, but take a look at the oil pump driveshaft. It'll take maybe 3-4 minutes to get at it. I'm suspicious of the hex engagement, and perhaps the rivet up top. Let me know. Good luck.

 

Thank you for the quick response Mr.4spd.

The engagement of the Intermediate shaft and the oil pump drive socket are like brand new. We did check that last night. I put the impeller back in and tried like hell to turn it one way or the other and it was like new; no play whatsoever.

Thanks again!

 

I am suspect of the junk oil filter your running. Cut one open and see if you sucked it inside out. Run a Wicks or K&N filter. One other thing. With a high volume pump you will suck a 5 quart pan dry at higher RPM's and starve the main bearings. This will cause oil pressure lose. This can happen and you won't see any bearing material unless you cut open the oil filter.

 

bremereric,

Thank you, I have ordered the correct Wix filter and see what that changes.

-C.R.

 

What does anyone think about proper brand, type, and weight of engine oil for this old rig?

I keep reading I should run straight (dino) 30W in it, I don't know about that...

Does anyone have experience with this idea?

Also, does anyone know if the Dodge oil filters back in 1977 were a different type, like a "by-pass" instead of the newer "anti-backflow"?

 

You need to cut you old one open to check for bearing material. A new filter won't correct that.

 

bremereric,

Will do that tonight.

Thanks, -CR

 

I would not recommend straight 30w oil. It would have horrible flow characteristics at cold start up. Oil weight is determined by manufacturer based on bearing clearance for acceptable film strength so no metal to metal contact occurs. To heavy a weight is just as bad as to light.

x2 what Bemereric said above.

Use an ice pick or sharp awe to puncture non threaded side and let it drain. Place it on a vise and use a carpet knife or comparable tool and cut off the cover at the rim. Dont use a sawzal as it will cause metal splinters and shards and you wont see difference between two metals if there is bearing material in there.

I have seen the plastic ring from a quart bottle of oil in the crank case and the aluminum cover / seal on the larger bottles in the crank case too. Both will caused issues but they worked free to the pan and were in the screen on the pickup.

Also look at the grommet on the pcv / breather and see if the under valve cover side cracked off and is in there causing blockage.

Hope its something small. Good Luck!

 

PK1,

Thanks for the additional insight. I have to go over and get the oil filter. My buddy who owns the local NAPA is going to lend me his oil filter cutter so I should be able to tell something by tomorrow night.

Thanks again to all who have helped thus far, I appreciate it.
-CR

 

1977 Dodge 400 / 6.6L sudden oil pressure loss FIXED!

Gents,

I possibly solved the issue for good

I cut open the oil filter as you all recommended, and (fortunately or unfortunately) there was NOTHING in it accept oil...(see pic) So, I was still at a loss for what the hell was causing the oil pressure loss.

I then pulled the distributor and the intermediate shaft out. The intermediate shaft looks absolutely NEW (see pic). There is barely any shiny wear on worm gear! The pump that was in it was supposedly "new" and was installed by a local "expert mechanic" because I had been out of town. I then blew air back through the two channels leading to the pump, and got good easy pass-through in both. Then I ran a section of old speedometer cable from a '56 1-ton through the two channels, sort of fish-tape style, and they were clear.

FIX:
I bought a high-volume oil pump and a NAPA Gold filter. I ground the driver's side motor mount to clearance the taller pump body. I welded up my own "primer tool" from a piece of cheapo 5/16 allen wrench welded to the end of an 18" piece of 9/32 cold-rolled rod that I polished with steel wool and carb cleaner and oiled-up prior to inserting it. The new pump took a prime almost immediately and so far, it is working fine. It gets 40-psi at idle (at op. temp.) and approx. 70-psi running.

So, I guess we'll see. It's been two weeks of daily driving and no complaints...

Thanks for your ideas friends :drinking:

 

Excellent idea! and nice FIX!! Glad you got it running correctly.

 

Just be carefull with that high volume pump. At high rpms in 5900-6000 rpm range you can suck a stock 5 quart oil pan dry and starve the main bearings. Been there and done that. You should run a 7-8 quart pan with a high volumne pump and maybe a 1/2" pickup tube.

 

bremereric,

Thanks, that makes sense, I didn't think of those things.

Where is the best place to get those parts, Jeg's, Summit?

-C.R.

 

Since yours is truck rear sump it may be hard to find one.

 

Ok, again, I thought I had it fixed, apparently I did not...

I have figured out that the pressure relief spring in the pump is sticking open and/or the spring is wearing out and weakening (not holding the valve shut) after a couple of weeks.

I have replaced the pump in this truck 5 times now, with five new pumps (at the wishes of the owner), and each time we get the same results, it works fine from the first restart and for 3-4 weeks and then it loses ALL pressure.

So, I did an experiment. I cut a piece of brass rod to replace the pressure relief spring and to not allow the pressure relief valve to open. I got normal oil pressure for about 3 minutes and then it blew out the oil filter seal.

When I had the pan off of the motor before (pictures in previous posts), I blew high-pressure air through all of the channels associated with the oil pump. The air flowed freely so, I figure there is nothing solid blocking the oil channels from the pump to the crank. What the hell would cause it to get so much back-pressure it would blow the filter seal, yet let air pass freely? :banghead:

To make matters worse, of all the pro mechanics in Colorado Springs, I cannot find anyone who has enough knowledge about the Dodge 400/440BB to help me out.

Y'all are my only hope. So, thank you for all the advice thus far.

I am ready to just pull and disassemble the damned engine but I'd really rather not if it can be avoided. There's nothing like disassembling an engine with 56,000 original miles on it. However, the owner, being a particular type of moron, used to like to floor his "Colorado winter morning cold" engines to "warm them up". He did so until I caught him at it and threatened his life...literally. The man is dumb but his checks never bounce so, whatever.

Could a bearing be partially spun? If it was, would it make these kinds of problems? If I do pull the motor, what should I be looking for (other than the obvious spun bearing) anything not easily caught without testing with gauges?

 

bremereric,

I have gone back to the stock volume pump because with either pump, the process of failure is the same, good pressure with new pump and failure after 3-4 weeks. As I described in my last post, I believe the pressure relief springs are failing.

Any ideas on this theory?

 

Any leaks?

 

Is your pressure gauge electric or mechanical? I read through the thread but I may have read over it.

 

You have replaced HOW MANY??? pumps? This is ridiculous

Let's get to basics.

Oil filters on these engines can NOT cause total pressure loss, unless two things happen AT THE SAME TIME

1 the filter would have to somehow become completely and utterly clogged

2 the filter bypass (not the pressure relief) that is built into the filter would have to fail closed

I'm wondering if you have a crack, either in the block or the pickup tube, that is allowing air to enter, losing prime?

One way to check if the pump is doing ANYTHING is to operate the starter after REMOVING the filter. The filter is the first thing the pumps sees at it's output, so if you can get "oil on the floor" with the filter removed, this means the pump is turning and doing "something."

There is an oil ring on the snout where the pump enters the engine. This must be present and unbroken. I do NOT recall that a failure of this O ring will cause total pressure loss, I believe it will just cause "some" loss.

Investigate if damage from hitting the motor mount is cracking the pump??

I am assuming, and dearly hope, that you are checking pressure with a mechanical gauge.

The chances of relief valves continuously failing so many times in rapid succession are less that the chances of you winning millions at the lottery. In other words, zero.

I don't remember how a B/RB intermediate gear goes together anymore, but it would be worth replacing if you have not. I can't imagine this causing these symptoms.

Have you torn down the "failed pumps?" Is there evidence of scoring, indicating dirt or debri? Any damage or debri in the relief? Even if a relief "failed" there should be SOME oil pressure. Ask yourself "how" is a relief going to fail? If the spring was to break completely, yes, no pressure. But if it simply got some debri caught (which should not BE there!!) in the relief valve, it might have lower pressure, but not NONE.

If you take these pumps apart, you can easily see where everything flows, because of their construction. "Several" problems are eliminated on these pumps because they are external. That is, a gasket failure on the pressure side will cause an external leak, where other engines would be leaking oil back into the pan. So you can SEE these types of failures, including the pump--to -- block gasket.

You have a shop manual? They detail how to inspect these pumps

 

I was just waiting for the MAN to chime in on this one....

 

I remember reading somewhere about a 440 had some kind of adapter on the oil filter was causing a pressure loss..

 

sounds like excessive bearing clearances or an oil gallery plug or something can really be plugged up
drop the pan and break out the plasti-gauge

 

A friend had exactly the same problem but it was with a small block , he had glass beaded the intake & the glass bead was stuck between the heat deflector plate under the intake , the glass bead was continually falling out of the intake & would get into the oil & jamb the the bypass spring & lose all pressure . is there any chance something was not cleaned properly like this ?

 

Next time it loses pressure, use the priming rod to see if you can restore it. Also, get a gauge to see how much pressure it has at normal idle speeds. If you need another 400 engine, I have a few.

 

And sounds like it may have excessive bearing clearances, causing the oil pressure to drop to 0 when hot. Again, a gauge would be very helpful here.

 

You will probably find that the pressure is gradually getting lower, and when it drops to 0 PSI, then the lifters start to make noise. Back in the 60s a friends Mom had a 383 Fury. When it ran low on oil, and she went around a curve, the oil light would come on. And the lifters would clatter. Then on a straight away, the light would go off and the lifters would quiet down. Ha Ha! Thats when I realized how tough these motors were. Hey you might try checking your dipstick. I have seen a too long one put in, which made it read full when it was almost empty!

 

Hello again all,

Sorry to be so long in responding, I just got back from 90days overseas.

Thank you all for your continued advice!

440roadrunner:
I have inspected all 5 of the failed pumps I have installed on this thing and in all 5 cases, I can't find any sign that there is anything wrong with them accept the bypass spring gets weaker over time; no metal shavings, no scoring, no heat damage, no damage whatsoever.

Worst part is, as I described in my last post, when I blocked that bypass valve, it blew the seal on the oil filter and put 2 qts on the ground within 30 seconds of startup.

I WISH I could find some metal somewhere. There's none anywhere; no simple answers :banghead:.

To try to answer everyone's questions:
- No external leaks on the pump or engine
- No damage to pump, pump gasket, pump stem O-ring (was extremely careful)
- Using mechanical oil pressure gauge
- I have not checked the dipstick length, but I have drained the oil and there was at least 5-qts in it the last time I had this issue. The engine itself has low (42,000) miles on it and fortunately has no gasket or seal leaks. Anyone know the factory length of the dipstick??
- No adapter on the oil filter. Just the pump itself.
- NOTHING in the oil pan every time I remove it. (I really wish there)

I am going to pull the pan (again x3 ) this week. Fortunately I bought the good reusable rubber pan gasket...

Garys69RR:
I'm going to pull the caps and see what the bearings look like. Because, as I described in a previous post, I think I have a partially spun main bearing. The owner is an IODIOT and was giving this poor engine about 3000rpm pedal-stomps in order to "warm it up" in -10-15deegreee Colorado winter weather. I think he started to spin a main, that's all I can figure. Something seems to be moving and blocking the high-pressure side of the pump. But yet there is no noise to indicate a bad main bearing.

I will look for cracks in the oil pickup tube and bearing clearances this week.

Thank you all

 

Keep us informed. This has me curious

 

What brand of pumps are you using?
Melling is the only pup to use IMO , I have seen other pumps that will not reprime after a simple oil change . When you have oil pressure how much pressure do you have ?