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Discussion Starter #1
Just drove home a 1989 Roadtrek Class B motorhome built on a Dodge B250 body and engine. I haven't bought any repair manuals yet but I think it's a 318 engine with 119,000 km on it. The transmission has been rebuilt and the previous owner has repair records since 2003. No major engine repairs are listed.

Driving it home today for the first time I noticed that the oil gauge was reading only one bar above the bottom line. Thinking it was low on oil I checked the oil dipstick when I got home and it looked to be slightly over full.

Now I'm wondering what to check next.

I've never had a vehicle with a gauge but I assume it should be reading somewhere in the middle of the gauge like the temperature gauge does.

Before I try a new oil pump are there other things I can look at to see whether I'm getting a faulty reading?

thanks
 

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DO NOT FEED THE TROLLS!
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hmmm... Obviously there's a sending unit, and however the wiring is set up to the gauge. I don't know if theres another test port that can be accessed, one may have to either figure out how to hook a meter right to the sending unit or else try a new sending unit to see what it reads.
 

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Measure the actual pressure with an accurate mechanical gauge to see if the low indication is real or not. Sending units do get tired and dash gauge calibration can fail.
What oil is in there? A 10W-40 may bring pressure up.
If it is an engine wear problem, the oil pump itself is probably OK (best lubed part of the engine), but is unable to keep up the oil volume necessary to lube the excessive clearances of worn bearings, etc.
Spec is probably a minimum of 4 psi warm idle. Is the engine quiet?
 

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First thing I wonder is why is it overfull? Does the oil smell?
Overfull may mean that it was actually overfilled. It may also point to excessive fuel or worst case antifreeze. Any of those three would usually produce a low oil pressure reading.
A simple oil change can help a lot and you should still have an oil light on the dash along with the gauge. Have you ever seen the light come on?
 

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Discussion Starter #5
It's a new purchase so I'm just starting to feel my way around the vehicle. At this point things like an overfull oil pan are things I can speculate on but can't explain.

I'll try to test the sending unit over the next week. That would be the best case since it looks like a lot of work to drop the oil pan to access the pump.

I've bought fresh 10 W 30 to change out the fluid that's in there now. The guy in the local store couldn't even guarantee me the filter would fit. I'm just starting to see the pitfalls of dealing with a vehicle this old. Not regretting the purchase yet. Should be lots more questions on this forum coming up though.

At this point I still have to finish a safety, pay someone to get it appraised so the government can tax the vehicle for the 8th or 9th time and make sure they get every cent they deserve. This still boggles my mind...but that's what has to happen on vehicles in Ontario older than 20 years. Finally it has to pass a smog test. This will certainly identify whether there's more to the oil issue than a bad sender or oil pump.

Although I initially trusted the nephew selling the vehicle on behalf of an elderly uncle, the more I look at things the more I wonder whether there's an extra 100k or two on the five digit odometer despite his claim that it's just 119,000 km. Although we have to spend $20 on a used vehicle information package here, there are no odometer readings listed. Very frustrating on old odometers that roll over at 100k.

Despite the things I need to fix and the mystery items like the oil pressure gauge, it starts up right away every time and behaves quite nicely on the road. For something that's heavier than a small tank, from what I can tell, anyway.

I've got my fingers crossed that I can get it on the road and take my kids to California this summer without doubling the van's price in repairs.

As always, thanks for the tips.
 

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DO NOT FEED THE TROLLS!
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This is the compatible oil filters list that I made for my '82 Dodge D350 318 and also works for my '78 Chrysler Cordoba 360...

K&N HP-2004
Fram 43 Series
Pennzoil PZ7
Pentius PLB16 or PLB43
Bosch 3402 or 72198
Mobil M1-204
ACDelco PF13
Advance Auto AA16
Purolator L14670 or PL14670
Mopar MO090
STP S16
Motorcraft FL300
Valucraft V16

I make no judgement on the relative quality of the filters, though I like the K&N for the hex thing they weld to it to make removal easier.
 

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Discussion Starter #7
Yep the filter from the teenager at the local hardware store was too small. I think I'll be done with that place for a while. When a pair of parking brake cables I asked them for arrived it turned out they set me up with a couple of hardware kits instead of the parking brake cables I asked for.

Luckily I was up at the local Chrysler dealer yesterday picking up a gallon of ATF (I found a quart of dexron under a seat so I figured I'd better swap out the slop in the transmission) so I asked about the filter since the one I had was smaller than the one from my old caravan.

Ended up with a Mopar filter which matched the one I pulled off and fit just fine.

Unfortunately I also discovered that parts I later ordered from a very reputable and large local parts dealer had problems too. One of the pair of rear brake cylinders had two slits in one boot, straight out of the plastic bag (I installed it anyway due to time constraints) and one of the brake cables I ordered had the incorrect end on it. Didn't realize until the part was installed and the brake back together though. ugh. At least I know a guy there so it shouldn't be a real hassle to get another part.
 

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Discussion Starter #8
Down in California I took the van into a local garage that deals with lots of older vehicles to have the cooling system fixed and before he started that he said he wanted to have a look at the oil pressure because if really was low, the engine might need a rebuild and I could save myself some money by combining the jobs.

As soon as he looked at how low the gauge was reading, he said it was unlikely to have made the 2600 mile drive if the pressure really was that low.

He tested the gauge for resistance and got low and high readings of 5 ohms and 73 ohms which were normal. He put a mechanical gauge on the engine and got a 60 psi cold and 40 psi warm, which were also normal, so he suspected the sender.

When I picked the van up after the coolant work he said he managed to get the sender working again and the gauge now reads midway. I didn't ask for details of how he got it working. I assume it was corroded.

The best part is he didn't charge me for the inspection or the fix. Maybe the $1600 I spent on the other reapairs covered it.
 
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