QuestionQUESTION: My 150,000 mile 2000 Discovery II started leaking antifreeze @ the head gasket, passenger side nearest the firewall. I have owned this since new and have done the routine MX on it.
I made plans to have the gasket replaced but in the meantime, while a family member was driving it, they allowed it to run low on coolant, but shut it down when the red light on temp gauge started flashing. After allowing it to cool, and replenishing coolant, it ran normally.
Assuming the worst that a head was cracked, I purchased replacement head sets from Atlantic British, plus considering the mileage it did not seem unreasonable some valve work may be coming.
At the same time, I had timing chain & gears, water pump, head bolts & lifter rods replaced.
A visual inspection did not reveal any cracks on the heads after they were removed.
Also, my mechanic did say the engine interior had a sludge build-up when he opened it, though what I saw on the heads themselves when I returned them was not what I would say is a heavy accretion, particularly for an engine with this mileage. For the record, oil changes were typically done in 5000-6000 mile range with 10W40 oil; Since I live in a rural setting & it is 20-25 minutes into the city, the engine has always been operated at normal operating temps and not just for a few minutes and then shut down.
Problem: The vehicle runs well now, except it now has a low oil pressure issue.
At idle, the low oil pressure light comes on (turns off @ 1000-1100 RPM) and the lifters apparently start collapsing. Once the RPM increases, valve train noise goes away and all seems audibly OK.
For a brief period, the engine made no valve train noise, though the low oil pressure light would come on at idle, particularly after the oil was warm.
I drove it @ 50 miles and changed the oil/filter from 5W30 back to 10W40. This since the engine had been open and there is always the chance of debris finding its way in, possible defective oil filter and changing oil weights. No perceptible change.
I took LR back to my mechanic and, as I understand it, he placed an apparatus on the oil filter housing that monitors oil pressure. He states the pressure comes down to @ 5 PSI at idle and is 45-50 PSI @ 2000-2500 RPM. Also, the oil pressure fluctuates @ 15 PSI given a constant engine speed.
These numbers are after engine is warm.
I am seeking help diagnosing the new low oil pressure issue, which never existed before the engine was opened.
SOOO, why the new low oil pressure issue and what to fix it?
Thanks for your help!
ANSWER: It certainly sounds like the engine sustained some damage when it was run low on coolant. I would remove the front cover and check the oil pump. I'd also remove the oil pan and check the main and rod bearings. I'd guess the answer to your question will be found in one of those two places; maybe both. One final possibility I'd mention relates to your changing of the timing gears. If you did that, the front cover had to come off. When you refitted it, the gasket may have been installed wrong, or the wrong gasket fitted. That could cause the problem too.
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QUESTION: John,
Thanks for your quick response!
As I mentioned I ran the vehicle AFTER it ran hot, but BEFORE heads were replaced, as I ran the vehicle for perhaps 15-30 minutes. no overheating or noises such as I now am experiencing.
Your mention of front cover gasket issues seems the most likely given the vehicle ran normally.
I understand the oil pump can be purchased as part of the cover, or separately; it seems best to replace as a unit; is that correct?
Thanks again!
AnswerI did note that you ran the car after the overheating incident; however, 15 minutes might not have been enough time to see a problem like this. Lots of time low oil pressure does not show up for 20-30 minutes when the oil heats up. The oil is slower to warm than the coolant.
As to the pump - it is an integral part of the cover in that model year, and is not serviced separately. The oil pump parts you see are for older trucks
