Odd Pressure/Temp problem

[bnesse]

My 99 (3.2) has recently started exhibiting an odd problem when it is cold. Until the engine warms up, I get no temp reading, and my oil pressure runs very high. The problem rectifies itself after the engine warms up, but it is disconcerting.

If it was just the temp, I'd guess it was a bad/sticky thermostat, but the oil pressure concerns and confuses me. I couldn't find anything resembling this in the archives. As anyone ever seen this? Or any ideas as to the cause?

Thanks,
-Brian

 

[NSX 3.0]

I have a similar problem with my 91 and chances are my oil pressure sending unit is bad. I talked to a couple NSX guru's and that is what they came up with they run about $160 with a NSXCA discount. Here is a picture of it located under the front spool valve.

 

[hlweyl]

Brian, when you say your oil pressure runs high, how high is it? and is this at idle?

 

[bnesse]

Yesterday, at freeway speeds, say around 3K RPM, it was pushing the upper limit of the gauge (maybe one tick mark from the top). This was higher than it had reached on Friday when I drove it. I believe it is also running high at idle, but not nearly so high as when the RPM's are up. Today, I left it parked.

I pinged the local service department today and this didn't ring a bell with the service advisor either. I've got an appt. scheduled (for next Monday ) just in case. Hopefully another solution will appear before then. If not, I'll post the results when I get them.

 

[hlweyl]

Typically, you do get higher oil pressure readings as rpms increase. What are you getting at idle and are you getting and check engine lights? Any other symptoms like smoke?

First thing I would do is check the oil pressure with a mechanical gauge. Check it at idle and again at higher rpms. Good luck

 

[Bilulan]

My 99 (3.2) has recently started exhibiting an odd problem when it is cold. Until the engine warms up, I get no temp reading, and my oil pressure runs very high. The problem rectifies itself after the engine warms up, but it is disconcerting.

Same thing happens for me. 98 - 3.2. It takes several minutes for the temp guage to start rising and then the oil pressure guage goes down respectively to somewhat expected readings. At idle the oil pressure guage reads 6's and under anywhere from 2k to 7k rpm's it goes to 1 tick below max (until the car is warm)

I have one additional symptom. If I start from cold, I have to let the oil pressure guage rise all the way up before I can attempt to let out the clutch while in gear. Not that the two things are correlated, just providing a specific points of reference. If I try to start the car from cold and then immediately drive, the car stalls. Note: it takes about a 5 second pause (from cold) before I can drive.

 

[Paul]

You state that “when the engine is cold” the temperature gauge is not reading. This should be normal because the engine has not warmed up and therefore the coolant is still cold. The temperature gauge is actually working its just that the car is not warm yet. It takes a few minutes for the engine and coolant to warm up.

Without getting too technical, oil is affected by temperature. As the temperature of the engine rises the oil flows easier. Or another way to look at it, the oil is thick when cold and does not flow as easy. Your engine is designed to flow a certain amount of oil once the engine has warmed up. A cold engine (with cold oil) is not able to circulate the oil as well. The cold oil is thick and causes resistance which causes the oil pressure to go up hence the oil gauge reading extremely high even under moderate loads when cold.

Once warmed up the oil pressure gauge should register normal. You should also be able to watch the oil pressure gauge read at about the halfway mark at low rpm’s and increase as the rpm’s go up.

Both the symptoms you state in your FIRST post sound normal for a cold engine. As for your second post…you got me b/c your engine should be up to normal operating temps by time your reach the freeway unless you live right beside it. Have you checked your oil level? What oil filter are you using?

Paul

 

[bnesse]

David,
Yes, typically, my pressure increases with RPMs, but the gauge would typically be hanging around the mid-range and increasing to about 3/4 range under load, not spiking the top. No, there are no other symptoms whatsoever.

Bilulan,
Yep, that basically sounds like what I'm seeing. Though without the clutch issue. I'm not certain about the exact numbers, as I can't verify it at the moment, but they sound about right.

Paul,
Everything you said makes sense, and I agree with all of it. But, I've been driving this car daily for 10 months, and just noticed this within the past week. I'd like to think I'm more aware of my surroundings than that.

I should note that "cold" is a relative term in this scenario. The ambient temperature here is still in the 70's - 80's. Not cold enough to significantly thicken my 5W30 Synthetic to a point were it wouldn't flow normally.

And, yes, once warm the pressure registers exactly as you describe (and thus exactly as what I am used to it doing)

The first time I noticed this, I pulled off the freeway and checked the oil level. I also checked it later cold. If anything, it appears to be slightly overfilled. It certainly isn't low. I'm not sure on the filter, as I didn't do the change myself, it's whatever they put in at the shop. Since I am due for another change anyway, I thought about just going ahead and doing that to see if the problem disappeared. Maybe I still should...

Thanks for all the feedback and suggestions so far...
-Brian

 

[Paul]

Brian,

Yesterday when you posted I had understood your worries to be only when the engine was cold but it appears that you are having trouble with oil pressure once the engine has warmed up. If that is the case, the first two things I would check are the oil level and the oil filter.

If you have too much oil in the engine this could cause the problems you are stating. The oil level should read “approximately” the same level on the dip stick cold or hot. So if it’s too full hot, it’s still too full cold.

I asked about the oil filter in my first post b/c this too can cause the problems you talk about if the wrong filter is used. I have seen an nsx come from a (less than reputable) Acura dealer around here with the wrong oil filter installed. Make sure the Acura tech installs only the correct Honda/NSX oil filter. I don’t have time to search the part number but make sure that they install only the OEM oil filter for the NSX. If you are taking the car to a Quick Lube shop they most likely do not have the OEM oil filter. They will install whatever they stock so you will need to take them an OEM oil filter.

You stated that you think it “might have too much oil in it” and you are not sure if the filter is OEM and I don’t know where you had your last oil change. My suggestion (which you said you are doing) is to take your car to the dealer and have them change the oil and the oil filter. Make sure they use the correct filter and then check the oil level when you leave. Once the car warms up I would think that it should be back to normal.

BTW my oil pressure gauge reads very high at high rpm’s even when the engine has warmed up to operating temps. But I have never seen my oil pressure gauge pegged out as you state.

 

[Paul]

Brian,

One more thing…I think you though I meant “cold” as in outside (ambient) temp. In my first post I am referring to the actual temperature of the engine. While the ambient temperature does have an effect on the actual engine temperature, the engine is designed to maintain a certain temp regardless of the ambient temperature. I believe our thermostats are set at 180 deg F (but don’t quote me on that). So even if it’s a cold day (say 40 deg F outside) the thermostat will not open as much thus restricting the coolant flow so that the engine can warm up to and maintain 180 deg F. On a hot day the thermostat would stay open all the way thus allowing as much coolant to flow as possible trying to keep the engine temp at 180. I hope I am not getting too basic. I am just trying to help.

 

[bnesse]

Paul,

No worries. I'm not easily offended, and I do appreciate the help. I have a good basic understanding of engines, though these days I usually let someone else do the work for me.

I did assume you were talking about engine operating temp. I just threw in the ambient temp as a data point.

I guess the difference between cold and warm, in this context, is how long it takes to get "warm". Usually, when I get on the freeway and notice the temp and pressure gauges, it's riding in what I would call their "normal" range (say mid range for both around 3K RPM). Lately it seems that I'm 3-4 miles further down the road, and I'm seeing low temp and high pressure at the same 3K RPM.

I see I didn't state it clearly, but yes, it does appear to be overfilled cold. So that sure could be the problem. And the info on the oil filter is good to know. And, yes that could be the problem too. The oil change was at a Quick Lube type shop, and I don't know for certain that they have the appropriate filter (though they claimed they did when I asked the first time I went in).

I just hate to think that this has been going on for the last 3000 miles, and I just noticed it for the first time last week I thought I was more observant than that.

I'll have to look into the oil & filter thing and see if that's where my problem lies.

Thanks again,
-Brian

 

[bnesse]

I had the oil & filter replaced yesterday. The oil pressure doesn't appear to be fluctuating as much as it was. (Of course it appears that they overfilled the oil too... why is it that you have to do it yourself to get the job done right? ). Since I had my wife take the car in, I didn't get the feedback on whether the wrong filter was installed previously.

Given the apparent improvement I guess I'll chalk this up to a bad filter and maybe being less observant than I thought I was. I guess I'm going to have to start changing my own oil again...

Thanks again for all the help and suggestions.
-Brian