454 TBI - A couple questions

[kickdeez]

I've been battling a few issues since I got the top end of my motor put back together after having to replace the heads due to burning coolant (ended up being a bad head rebuild job). Long story short, i have replaced the bad heads with new (rebuilt) heads and got the truck running again. It is not burning any coolant, and after some tweaking here and there, it appears to be running pretty well. My questions are as follows:

1. What is the typical operating range for oil pressure in these motors (idle and wide open)?

2. I have flushed the cooling system (with the thermostat removed) 4 or 5 times to try to clean out any residue from the top end rebuild. The water still seems to be getting discolored, and turning a slightly stained brownish color. Not dark stain, but still not clear water. Is that normal?

3. I started the truck up today and let it run in the driveway for about 10 minutes with the radiator cap off. It warmed up to a little over 220 while idling, with occasional revving to get it up to operating temp (currently no thermostat). When I turned the truck off, a considerable amount of water immediately started spraying out of the top of the radiator. Is this a normal occurrence? If not, what would cause water to gush out in that manner? To me, it doesn't seem like this should happen. But I'm no engine building expert, just a guy trying to fix a truck.

Thanks in advance for any guidance.

 

[bucket]

Don't run it that long with the radiator cap off, you will be fine. If the coolant was mucky and brown before, it takes a long time to get all of it out. If you can run it now and it still resembles coolant when you look at it, that should be good enough.

Mine have been about 25 psi at warm idle, and it increases with rpm. As long as you have 10 psi for every 1000 rpm, you are in good shape.

 

[kickdeez]

Thanks for the quick response. The reason I ask about the oil pressure is because when i initially start the truck up, the oil pressure gauge pegs out past the operating range (well beyond 60 psi - according to the gauge). After the truck runs for a while, the gauge eventually kicks down and reads about 30 psi at idle, but as soon as I get back on the throttle, the gauge rises rapidly and pegs out again past the operating range. I don't know if its a gauge problem, an oil pressure sending unit problem, or an internal problem. Any thoughts on this?

 

[bucket]

Someone could have installed a high pressure style oil pump, but more than likely it's a bad sender or inaccurate gauge.

 

[Skweegle89]

Mine pegs out at 60 all the time, but it's got a high pressure oil pump in it.


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[kickdeez]

I guess it is possible there is a high pressure oil pump in there. I really don't recall what kind of pressure it was reading before I pulled the heads. I can't say that I remember the gauge pegging out when I bought the truck. And I think that's something I would have paid attention to when I got it. For grins and giggles, lets assume that it does not have a high pressure oil pump in it, and that the gauge was not pegged out prior to replacing the heads. That being the scenario, what possible causes (if any) would there be for the gauge to read like this?

 

[bucket]

I guess it is possible there is a high pressure oil pump in there. I really don't recall what kind of pressure it was reading before I pulled the heads. I can't say that I remember the gauge pegging out when I bought the truck. And I think that's something I would have paid attention to when I got it. For grins and giggles, lets assume that it does not have a high pressure oil pump in it, and that the gauge was not pegged out prior to replacing the heads. That being the scenario, what possible causes (if any) would there be for the gauge to read like this?

If the sender got bumped or bent during the work, it could very well be faulty now.

 

[kickdeez]

Where is the sender located? I have no doubt that it is possible something (or many things) got hit or bent in the process. There was a lot of crawling around on the engine, legs and arms contorted and placed for balance, as well as a lot of heartache and swearing that went into this job.

 

[bucket]

It's probably up front on the side of the block, driver's dide. Behind the power steering pump area. Could be back by the oil filter area though.

 

[kickdeez]

Perfect...i know exactly where it is. I remember seeing it, and thinking that's what it was.

Thanks for the help! I'm going to check the wires to the sender and go ahead and replace it. I'll let you know if that fixes it.

 

[kickdeez]

I replaced the sender last night. After doing so, I started the truck up, and the oil pressure read 60 psi. After i let it warm up for about 5 minutes or more, it eventually (and slowly) settled in to about 30 psi. It seemed to be reading fairly accurately (as far as what I would expect to see) once the motor was up to operating temp. But below operating temp, the pressure reads high. Any thoughts on this?

 

[bucket]

That's perfectly normal. The oil is thicker when cold so the pressure is higher.

 

[kickdeez]

Oh, and also, after letting the truck sit in the driveway running for about 10 minutes yesterday (with radiator cap on this time), the temp was up to about 210 -220 again. When i shut the truck off, i started to get a constant water drip out from under the radiator cap due to pressure build-up. The truck did not do this before I did the top-end rebuild. I was also checking the upper radiator hose while it was running. I could feel some water running through it, but it was not completely full, nor was it very pressurized. Is this something to be concerned about? I don't think it should really get that hot just sitting in the driveway, especially with no thermostat in it.

 

[bucket]

Have you actually driven it yet, or just let it sit and run? First, it sounds like your radiator cap does not seal properly, it should not leak no mater how much pressure there is. Second, you could have an air pocket in the system after your mishap with the coolant overflowing when hot. Let the motor cool completely, then make sure the coolant level is up at the top of the radiator. If not, top it off then put the cap back on. If it only runs hot while sitting and is cooler while driving, the fan clutch may be worn out.

 

[jeffro308]

Are you running a fan shroud?