Hi Guys
I am writing from Cape Town, South Africa. I have an 88 model Euro spec Supra MA70 with the 7MGTEu engine installed. Before I start, just wanna say that I have built and rebuilt a few engines in my days and am a qualified Mechnical Engineer as well. My career is in IT though, so cars are a hobby but I know enough to get by and have a decent home workshop to do most jobs myself.
So to my problem, this is the first time I have experienced something like this, thus the advice.
I did an engine rebuild on my worn 7MGTE with new rings and bearings after I knocked the big end bearings due to running the engine at high revs with too little oil - my fault that I didn't check oil knowing that my valve stem seals were passed their due date!
Once the engineers had it, I had to source another crank as mine was bent after the knock so I found a complete stock sub for little money. After rebuilding the sub with new bearings and rings (thankfully cylinder bores were well within spec), I fitted new KING bearings and Grant rings and had all the clearances checked and double checked by the engineers to within factory specifications.
After assembly, I fitted a new EQUUS mechanical gauge as I am running an aftermarket full management system which tach adaptor so my oil pressure gauge never worked before and I wanted to make sure all was well. Now, I find that the oil pressure on a cold-start would be fine at around 3 bar but as the engine warmed up the oil-pressure would drop to the 0.5 bar mark. After a vew blips on the throttle, the oil pressure would drop to zero and be so low than you could literally see the air pockets in the clear oil line. Naturally, I removed the engine and sent it back to the engineers. They checked clearances again and I checked and all was correct at which point they adviced me to fit a new oil pump even though my used one just needed a slight pump body shim to be within spec and was boosted on the relief valve.
I replaced the oil pump with an original Aisin unit and boosted the pressure valve again a 3mm spacer behind the spring and still the exact same result. Pressure is fine when oil is cold but when operating temperature is reached oil pressure drops. I am using a 10W40 Castrol Futron Semi-Synthetic Oil which in our climate of 22 to 28 degrees C at the coast is more than adequate for this engine.
Then some idiot who claims to know the 7MGTE told me that the engine has high volume low pressure and that it is fine to drive the car like that and after 1 2nd gear prod in the boost (0.5bar boost currently) I heard a bearing rumble. Lifted the motor off the mounts, dropped the sump and replaced all the big end bearings again! Only bearing number 5 ran slightly with no visible damage to the crank. My conclusion is that this engine is not getting the oil feed it needs.
Another source told me that the oil cooler adapter on the side of the engine also has a pressure relief valve and this could be the only other source of my problem. Anyone have oil pressure problems caused by an oil cooler adaptor? I do not want to buy another motor as I have felt this 7MGTE in all its glory and on a measly 0.5bar boost it was really strong so I would like to diagnose this issue. I have already bought a used oil cooler adaptor but before I replace it would like to hear other experiences.
I have already followed the other advice on the forum regarding engine rebuilds and the oil pressure woes so this is quite frustrating for me.
Thanks guys and compliments of season to all
Turbo6Supra - Cape Town, SA
I am writing from Cape Town, South Africa. I have an 88 model Euro spec Supra MA70 with the 7MGTEu engine installed. Before I start, just wanna say that I have built and rebuilt a few engines in my days and am a qualified Mechnical Engineer as well. My career is in IT though, so cars are a hobby but I know enough to get by and have a decent home workshop to do most jobs myself.
So to my problem, this is the first time I have experienced something like this, thus the advice.
I did an engine rebuild on my worn 7MGTE with new rings and bearings after I knocked the big end bearings due to running the engine at high revs with too little oil - my fault that I didn't check oil knowing that my valve stem seals were passed their due date!
Once the engineers had it, I had to source another crank as mine was bent after the knock so I found a complete stock sub for little money. After rebuilding the sub with new bearings and rings (thankfully cylinder bores were well within spec), I fitted new KING bearings and Grant rings and had all the clearances checked and double checked by the engineers to within factory specifications.
After assembly, I fitted a new EQUUS mechanical gauge as I am running an aftermarket full management system which tach adaptor so my oil pressure gauge never worked before and I wanted to make sure all was well. Now, I find that the oil pressure on a cold-start would be fine at around 3 bar but as the engine warmed up the oil-pressure would drop to the 0.5 bar mark. After a vew blips on the throttle, the oil pressure would drop to zero and be so low than you could literally see the air pockets in the clear oil line. Naturally, I removed the engine and sent it back to the engineers. They checked clearances again and I checked and all was correct at which point they adviced me to fit a new oil pump even though my used one just needed a slight pump body shim to be within spec and was boosted on the relief valve.
I replaced the oil pump with an original Aisin unit and boosted the pressure valve again a 3mm spacer behind the spring and still the exact same result. Pressure is fine when oil is cold but when operating temperature is reached oil pressure drops. I am using a 10W40 Castrol Futron Semi-Synthetic Oil which in our climate of 22 to 28 degrees C at the coast is more than adequate for this engine.
Then some idiot who claims to know the 7MGTE told me that the engine has high volume low pressure and that it is fine to drive the car like that and after 1 2nd gear prod in the boost (0.5bar boost currently) I heard a bearing rumble. Lifted the motor off the mounts, dropped the sump and replaced all the big end bearings again! Only bearing number 5 ran slightly with no visible damage to the crank. My conclusion is that this engine is not getting the oil feed it needs.
Another source told me that the oil cooler adapter on the side of the engine also has a pressure relief valve and this could be the only other source of my problem. Anyone have oil pressure problems caused by an oil cooler adaptor? I do not want to buy another motor as I have felt this 7MGTE in all its glory and on a measly 0.5bar boost it was really strong so I would like to diagnose this issue. I have already bought a used oil cooler adaptor but before I replace it would like to hear other experiences.
I have already followed the other advice on the forum regarding engine rebuilds and the oil pressure woes so this is quite frustrating for me.
Thanks guys and compliments of season to all
Turbo6Supra - Cape Town, SA
