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Low Oil Pressure and Overheating

11K views 27 replies 11 participants last post by  KThaxton 
#1 ·
I have changed the oil pump in my RC and I still have low to no oil pressure and the engine is boiling after driving 20 miles or so.  I do have some leakage I believe is coming from the rear main but not enough to cause low pressure, I would think.  I am losing about a quart a month at most.  The oil pressure gauge has always shown low pressure but not this drastically. The pressure completely drops out when I come to a stop. The oil light will go off when I put it in neutral. What could be causing the low oil pressure and severe overheating? I have looked thru dozens of postings and have not found one that was exactly like my case.  Planning on replacing both main seals and valve cover gaskets.  But this certainly won't stop the overheating.  Anyone have any solutions?
 
#2 ·
  Well for starters lets start with the radiator is full,  the belt is on,  the fan is turning,  if it's a clutch fan it's working correctly or it's spinning slow?,  your radiator is clear....nothing blocking it,  plastic bag, paper, ect. 

  Oil psi,  when you replaced the pump...did you replace it with a HV pump, did you clean or replace the pick-up tube,  did you clean the pan thoroughly,  did you use a motor douche type cleaner in the oil prior to or after the new pump was installed
 
#3 ·
The oil is the primary coolant for engine internals. If oil isn't circulating, that causes major friction and friction builds lots of heat. Did you soak the pump in oil prior to installation? Did you prime the system before start up? I had a similar problem with my 383. I didn't seal the threads on the pick up tube and I didn't thread it in far enough, so when the pan went on the pick up was smashed against the bottom of the pan and too far in the corner. It would have good pressure on start up, but would soon drop to almost nothing, and the engine would get hot fast! I caught it in time and back tracked, then corrected it, but big block truck motors you have to pull the engine to rotate the pick up tube. If you have run any distance in that condition, you probably have metal chunks in the pan.
 
#4 ·
Yes to all of the above. Cooling system is perfect.  Engine was cleaned out before drained. Put in new standard pump and new filler tube and screen. No change in performance or pressure or temperature. After another look it seems the tranny is leaking, but I already knew about tranny problems.
What now?

The pressure has shown low for the 6 yrs I've had it. I have driven maybe 5000 miles since the overheating started but engine started performing badly about 250 miles ago. And very little metal found in pan.
 
#5 ·
  How and when does it overheat,  at speed or when in traffic,  explain how it happens,  is there any sign of water in oil or vice versa,  was anything else changed recently 
 
#6 ·
It always overheats. There are no circumstances that it doesn't run hot. It only has to be running long enough to overheat. Again, the cooling system is perfect. No problems with the oil itself. Not even sure that it has ANY leaks of any kind at the moment. Pretty sure the tranny pan is leaking though. Only have oil on the tranny side, not in front of the bell housing. No smoke. No runs. No drips. Only errors. ???
 
#9 ·
Well, another thing to consider, if you are using a thin oil, and the engine is overheating, your oil pressure will go away when it gets hot, and it will only compound the overheating problem.

If I use 10w30 in my truck, hot (180) at idle it reads 10 psi, if I use 30w, hot (again, 180) at idle it reads 17 psi.

Are you sure the water pump is not a reverse rotation style ??  Cuz if it is, it will not pump on your engine.  Does the radiator heat up quickly with the engine, or not ?
 
#11 ·
ED's questions are most relevant...  especially the fan clutch function?
and shroud... is your fan shroud in good shape?
and,...  I'd add...
SIMPLE STUFF FIRST:  have you pulled and tested the thermostat ?

How many miles on that water pump?
The vanes do just plain wear down with many miles...

Notes:
318s have notoriously low oil pressure at idle.
I wish you had installed a high volumn pump, but stock is OK.
Overall, losing one quart of oil a month is no big deal.
Clean the engine really well, then look for the oil leaks.
The rear main seal doesn't have anything to do with oil pressure.
Your factory oil pressure gauge sender may be poohing out.
 
#12 ·
I am currently using 10w30 and have been for a couple years, 10w40 before that.  Water pump is the correct direction type. I need to get a mechanical oil pressure gauge and a compression gauge and check those out. I work on call and money is extremely thin now. Just checked the plugs and they are wonderful. The timing chain needs to be replaced, think it is the original. Please send me some money so I can do all this stuff!  ;D  I am begining to think there may be something stuck in the oil canals or whatever they are called. The water pump and thermostat I replaced a couple months ago. Even put in 160 degree therm to make sure it would circulate early. Coolant is having no problem circulating. Fan is in good working order. Timing could be causing the overheating, but what about the pressure? Don't think the timing could cause oil pressure problems unless it was far off. Going to clean the engine with water hose(puts out pretty hard stream with our 40-60lb water pump.)

No checks please!  ;D
 
#14 ·
Alot of times running a low temp thermostat like you are using will actually cause more problems. The water just won't stay in the rad long enough to get rid of any heat, it will open and then stay open. Would also help too know where you are from so we could tell if environment is a factor, are you in the antarctic or the mojave desert? Probably be a good idea to check your timing also.
 
#15 ·
I'm in Texas, but it was only 103 degrees today.  8)  I just washed off the top of the engine and dried it as well as I could. Then started her up and opened up the throttle a bit for about 15 seconds hoping the oil pressure might rise a bit. It didn't.  I let it idle for less than five minutes. I found a oil leak under the EGR valve and between it and the valve cover. Not sure which is leaking though.  Also, blew the upper rad hose right above the thermostat.  Cooling system is definitely working, but getting way too hot way too quick.
 
#16 ·
Well, since that hose is off, look inside it to see if it was split inside and somehow blocking flow. :mad:

When you look in the radiator to see the water flow, do you see any bubbles...  I'm suspicious that, since it is heating up so quickly, you may have a leaking head gasket...  sorry to say so, but that would cause your symptom.  :'(

Some garages have testers that read the coolant for combustion byproducts...  ???

Then, since you're there... change that thermostat back to a 190... as all engines since the 70s have been designed to use a 190, 200 or 210 thermostat...  and make certain you put it in facing the correct way.  ::)

 
#18 ·
The spec's are:
Min oil pressure at idle = 8psi
operating range= 30-80 psi at 2000 rpm

A high volume oil pump wouldn't increase oil pressure, but would compensate for increased tolerances due to wear on bearing surfaces. Try a manual oil pressure gauge to rule out the current gauge, sometimes the sending units go bad. Is the oil filter new? A higher viscousity oil would raise the pressure if there is no restrictions in the galleys or passages. has the pan and pick up been checked?
 
#19 ·
Bubbles? Do I see any bubbles?  Only if you consider foam as 'bubbles'!  Opened up this rad cap after Smokey's reply and saw this thick foam rolling through the rad.  Also, when I took off the left-side valve cover there was fresh oil on top of the rockers. Would this indicate that there is at least some oil pressure?  Has started to idle irradically. Timing chain will be replaced ASAP.
 
#20 ·
mrick36 said:
Bubbles? Do I see any bubbles? Only if you consider foam as 'bubbles'! Opened up this rad cap after Smokey's reply and saw this thick foam rolling through the rad. Also, when I took off the left-side valve cover there was fresh oil on top of the rockers. Would this indicate that there is at least some oil pressure? Has started to idle irradically. Timing chain will be replaced ASAP.
sorry to break it to you but i do not beleive timing is your problem here, sounds more like smokeys diagnosis of head gasket may be right.

and yes the oil on top of rockers would indicate that you have oil pressure. i and several others on here would reccomend a mechanical oil pressure gauge, especially since dodge sending units are notorious for going bad or just plain reading incorrectly. then again i also understand the lack of funds issue.

if you decide to go with the mechanical gauge might i also suggest a mechanical temp gauge as well, you can usually pick up both gauges in a set alot cheaper than buying them seperately and both will be more accurate than your stock gauges.

i had a 360 awhile back that was doing exactly what you are describing, only read 10 pounds of oil pressure tops, and regardless of what i replaced it read 220+ degrees all of the time, even without a t-stat in (i know, i know, never run without a t-stat) within a week of all of this starting the drivers side head gasket went.

hope this helps a bit

eric

ps: let me do some looking, if i remember correctly i may have a spare mechanical oil pressure gauge lying around, if i do, then shoot me your shipping addy and you can have it
 
#22 ·
;D ;D ;D ;D ;D ;D ;D ;D ;D
FINALLY!!!!!!!!!!!   Not only was the timing just a hair off, but there was one thing I forgot.  When the radiator hose busted I never refilled the radiator with water.  Appearently I lost more water than I thought. Overheating problem fixed. When I hit the gas to test for power, I peeled out and hit 40 really quick(for this old thing).
I thank everyone for your help and suggestions!!!!!!!
;D ;D ;D ;D ;D ;D ;D ;D ;D

Will be shooting you that address soon.
 
#24 ·
i had a car in the shop the other day,knocking and sluggish to drive,it was down about 5 quarts of coolant.something needs to be said about regular maintenance............glad you got it figured out.
 
#25 ·
I'm having a similar problem.  I have an 89 RC with a newer Magnum 360 in it.  It actually has the original 318 intake on it.  I took it through some mud, caked the radiator, and overheated it.
When I got it home, I cleaned the engine, radiator, and replaced both head gaskets just for safe measure.  Immediately after the repairs, I've experienced low oil pressures, sometimes they go away when I revv the engine, but now it stays on all the time.
I still have the overheating problem, I noticed once that my upper radiator hose was bulging like a balloon, so I removed the thermostat and it helped the bulge but I still overheat.
The radiator appears to be in good shape, no missing fins, I now use oil like crazy, as well as coolant.  Any ideas?
 
#26 ·
Im betting its your head gasket.  Did you torque to specs?  When you refilled your radiator did you mix the coolant and water?  <---maybe a dumb question but ya never know.  Also you say that you cleaned everything off when you got home.  Did you let the engine cool first?  Or did you just start spraying cold water on hot metal?

Boo 
 
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