>Date: Wed, 15 Mar 2000 21:01:10 -0500
>To: Richard F Flynn <rflynn@dircon.co.uk>
>From: James Barrett <jamesbrt@mindspring.com>
>Subject: Re: Oil Temprature Question
>
>At 09:17 PM 3/15/2000 +0000, you wrote:
>>
>>My Tiger used to do this in traffic:
>> - idle briefly
>> - overheat
>> - leave puddles of coolant
>>
>>That problem seems largely solved, but I have a different problem which I
don't
>>completely understand:
>> - idle for much longer (though still somewhere south of 20 minutes)
>> - get rather hot - definitely +230F
>> - loose all semblance of oil pressure
>> - cease to run until cool
>> - doesn't lose any coolant
>>
>>Can someone explain to me what is happening here? Does it indicate a
mechanical
>>problem or is the oil losing viscosity or something else altogether?
FWIW, oil
>>pressure under normal circumstances is a robust 75 <whatever units are on that
>>dial>.
>>
>>Thanks in advance,
>>
>>rick
> Possibilities for low oil pressure when hot:
>(assuming there is not oil leaking from the motor)
>
> Crud blocking the oil pump pickup or pickup pipe loose?
>
> The oil pump has a pressure regulator valve in it. This is a simple
>steel piston backed with a spring. If the piston is getting hung up in the
>open position due to a skuffed piston or its bore then you would have no oil
>pressure. This is assuming that expansion of the parts contribute to the
>hangup. A loose plug that retains the spring could also be a problem.
>
>
> Too much gasoline in oil (if oil hasn't been changed in a long while.)
>
> Some aftermarket remote oil filter adapters have a thermal operated
>valve that is susposed to open when the oil gets hot to pass the hot oil
>through an oil cooler. If you have somehow installed this type of adapter
>incorrectly the oil from the pump may be going directly back to the sump
>instead of to the bearings.
> Likewise if you have a big oil cooler and low oil level it is possible
>that the above adapter is taking so much oil out of the pan that the oil
>pickup is sucking air. The thermal valve only operates when hot. Check
>your oil level immideately after you shut off the motor when you have lost
>oil pressure.
>
> There are a couple of pipe plugs near the timing chain that should be
>tight. If you lost a plug then the oil would flow directly down into the front
>of the oil pan and you would have minimal oil pressure. This should also have
>an impact on the pressure when cold however.
>
> A cracked block ( crack into oil passage) could open at high heat.
>
> Assuming you have a stock oil pressure gauge, then it is operated
>directly by the oil pressure so the only possibility ( I can think of) of heat
> related problem is that the oil pressure line ( 1/8" copper or plastic) is
>somehow getting blocked. If you have an electric sending unit then that could
>be defective.
>
> The reason you can not start the motor when overly hot could be
>vapor lock , badly skuffed pistons, defective/overheated starter, loose ground
>strap from frame to motor, Corroded connections at battery, bad battery to
frame
>ground connection, bad starter solonide, bad ignition switch, the
>wires from the switch to the solonide or or defective ignition.
> This is assuming that you do not have a piston hydralic locked due
>to oil from an internal block crack or water from a cracked block, head or
>bad head gasket.
>
> If you can idle for 20 minutes before the problem occurs then never
>idle for more than 15 minutes. Shut it off and wait for the traffic to clear.
>
> If this were mine, I would pull the oil pan, check the rod and main
>bearings/journals. If the journals were not damaged I would install new
>bearings and a new oil pump. I use a high volume, not high pressure pump.
>I normally get 60 psi cold and 55 to 60 psi when warmed up with new bearings.
>
James Barrett Tiger II 351C and others
|