I have installed a new instrument cluster in my '84 Grand Wagoneer, due to the original having burned up in a fire.
Everything is installed and appears to be functioning; however, my H2o temp is well below the green arc, and my oil pressure runs at about
25-30 psi. It might reach 38 psi when cold, but I'm worried about it being that low all of the time. It doesn't seem to change with temperature. We've had zero-degree weather the last few weeks and now it's up in the 40s (F). I am running Castrol 10-30 oil.
As always, any suggestions, advice, etc., very much appreciated.
Temporarily install a mechanical oil pressure gauge to check what is really going on before you start replacing any parts.
Does the radiator and radiator hoses get too hot to touch? Let the engine warm up with the radiator cap off and then swipe the thermometer from the kitchen drawer and dip it into the coolant. What is the temperature?
Be sure to clean it thoroughly before you return it. If caught plan on replacing it without an disagreement you won't win.
A thermostat that is stuck open will slow or prevent the engine from warming up properly. It can be tested by removing it from the engine an putting it in a small pot of water on the stove. It should open shortly before the water starts to boil.
I'll do all that. I strongly suspect a stuck Thermostat; the only thing indicating against it is the fact that the heater seems to work OK, but we're probably talking about a difference of 30 degrees or so in the colling system, which may not make that much difference in terms of heater output.
When my temp gauge runs low, so does my gas gauge. I am not sure, but I think your Wagoneer uses the same type of gauges as the CJ7's. The temp and gas gauges run off a mechanical voltage regulator. Mine has a bad attitude. Well, it is actually a bad contact on one of the pin rivets inside the gauges.
I don't know if this will help, but here is a good page on the CJ gauges:
formatting link
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: N>
That does help, thanks. And quite often, when one guage is reading low, they all are. That's why I have not yet begun to worry too much about the oil pressure reading.
As others have suggested, if you're worried about the oil pressure shown on the dash you should check it at the block with a real mechanical gauge. I haven't checked but you might even be able to rent a proper oil gauge from your local chain retailer (Autozone, etc.) -- it isn't a tool you're likely to use very frequently. Keep in mind the gauges on the dash were never designed to be diagnostic tools, they're really just indicators and the numbers on the dial might just as well be letters. Not that there's anything wrong with that, mind you. If you know that when the gauge says "25" it really means "within recommended range" and it keeps on lying to you like that for the life of the engine you're fine. It will still warn you when the pressure goes out of range and that's really what you want to know, the difference between 31psi and
33psi isn't significant. It's like the gas gauge lying about that 1/4 full tank -- _you_ know how much further you can go on it, it doesn't need to be gallon-accurate. Jeep oil pressure senders are notorious for going bad, but usually they simply fail to full on or full off.
The temp gauge might be another kettle of fish, or it might be the same one. You recently replaced the instrument cluster, so it should be the first suspect on your list - you don't know that it was in perfect order when it was pulled, you don't know that there isn't now a poor connection (either B+ or ground) to the cluster. But the cluster is going to be a pain in the ass to get to so start with the easiest, cheapest, least messy, cold and wet test first: The sender.
I'm guessing that you have a volt-ohm meter left over from your headlight switch adventure. Use the information on the Jeep CJ gauge diagnostics URL that Mike provided and test the coolant temperature sender's resistance. If you've got the 258 inline-6 engine the sender will be a small post pointing straight up at the very back of the head, hard up next to the valve cover, on the manifold side. It will have a purple wire attached to it and covered in 20 years worth of oil, grime, dirt, feathers and twigs. (If you've got any other engine you're on your own for finding the sender). Pull the wire off. If you have a range of resistance settings select a low one, 100 ohms or so if you can because you're looking for 2-digit values, not megohms. If you have an analogue meter touch the probes together and set the meter movement to "0". Now ground one probe on the block and hold the other one to the post on the sender. You should get about 73 ohms cold, if it is much more that a couple ohms higher than that the sender is bad. The system is counterintuitive: The lower the resistance, the higher the gauge will read. With the engine warmed up you should get between 13 and 36 ohms, so the value range is really very small.
If the sender checks out OK then it would be between the thermostat and the gauge cluster. My money would be on the voltage regulator in the cluster -- mostly because that's the most recent unknown and only partly because I hate to have antifreeze dribbling down my arms in winter. If, as Mike asked, your fuel gauge doesn't go very far up either suspect a bad voltage regulator in the gauge cluster -- and that would explain all of your low readings.
Good luck with your beast.
Oh, and if you do need to spill antifreeze, watch out for your pets. Dogs in particular find antifreeze sweet and tasty but it is toxic to humans, fish and other mammals. Surprisingly small amounts will destroy their kidneys and leave then dead dead dead in a matter of days or weeks.
Ah. I'd suspect either a bad connection to the cluster (either B+ or ground or both) or a bad gauge voltage regulator. This isn't the regular syatem voltage regulator, it is a little kludge that's part of the fuel gauge, it sends the gauges little pulses of power that are supposed to _average out_ to 5 volts. For CJs the fix is to replace the fuel gauge -- because the regulator is part of the gauge. I'd guess the same is true for your Full Size Jeep.
In my case, it is a bad connection inside the gauge. I bypassed the regulator externally with an electronic one I made and it only worked for a few minutes, then started reading 1/3 low like the other mechanical regulator in it's moments.
If it's like my '77 Cherokee, the CVR as it's called, is built into the temperature gauge. Another possibility is that the year model of Grand Wagoneer your new instrument cluster came from uses different sending units on the block than your original. Check with a Jeep dealer or parts house. You may just need to replace them.
Can't say for Jeep but some cars have an extra regulator that provides precise voltage to the instruments. If voltage in high/low they will read wrong. Sounds likely since all your guages are off.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.