Oil System Issues
08-21-08, 09:36 AM
#1
Oil System Issues
Backround:
Car is a '91 NA with 170K miles.
Prior to my purchase two years ago, the car was originally owned by a Mazda specialist (of somewhat dubious reputation) and then a series of unknown owners.
At some point, the engine was "rebuilt" but there is no documentation and a lot of questions about what exactly was done. My current mechanic has been familiar with the car since it was new (he used to work for the original owner).
After purchasing the car, I completely replaced the cooling system (rad/pump/hoses, etc.), full tune up (and lots of other non-germane stuff) and the car has been a very reliable daily driver- always starts and runs fine. Did not smoke at all, oil consumption right at a quart every 3K miles, consistent 16 MPG city.
It does have low compression (@75-80 PSI) and the oil pressure has always been low (@ 10-15PSI at idle (after warmup) and 40-45 PSI above 3K RPM- this is read from an aftermarket gauge, not the stocker).
So, I've been aware that this motor is in need of either a rebuild or replacement (Turbo or V-8?), but need more time to get my ducks in a row.
And, I repeat...the car runs fine, so I was hoping to eke out a few more months before crunch time arrives.
Alright- sorry for the extended exposition...
At the last oil change I decided to see if anything could be done about the low oil pressure and the easiest/first option seemed to be shimming/replacing the e-shaft thermal pellet, which is reputed to be good for an extra 10PSI.
I also opted to use 20w-50 Castrol GTX instead of the 10w-30 previously used.
Well, the oil pressure did increase- dramatically.
From a cold start I was seeing 75-80PSI (it's never read that high) and once warmed up, idle pressure was 25-30 and anything over 2500 RPM showed 60-70 PSI.
This was a completely unexpected magnitude of change.
Unfortunately, there are two bad side effects.
The most troubling is the oil temp which has also increased dramatically.
A few months ago the oil cooler thermostat was replaced, since then the oil temp has mirrored the water temp- pretty steady at @190°F.
Now the oil temp is running about 20° higher, even at low RPM boulevard cruise speeds. Highway speeds raise the temp to 220°F or so.
The oil cooler is hot across the matrix and I have no reason to suspect that it suddenly failed. Water temp has not changed.
Secondly, she's started to smoke noticeably.
Especially bad after sitting at idle (like for a red light), it clears up after a block or so but she never did this before.
It seems logical that the higher oil pressure is stressing the (probably worn) oil control rings/oil seals but we can't figure out why the thermal pellet replacement (from Rotary Aviation, I believe) made such a marked difference (practically doubled the pressure).
It has been suggested -possibly out of desperation- that I dump the 20w-50 and go back to the lighter weight oil, but it seems to me that would cause it to smoke even more, although I could almost live with that if the temp would come down.
Any thoughts/suggestions welcomed.
A rebuild/replacement is not possible at this time, looking for a short term strategy until the right thing can be done.
Car is a '91 NA with 170K miles.
Prior to my purchase two years ago, the car was originally owned by a Mazda specialist (of somewhat dubious reputation) and then a series of unknown owners.
At some point, the engine was "rebuilt" but there is no documentation and a lot of questions about what exactly was done. My current mechanic has been familiar with the car since it was new (he used to work for the original owner).
After purchasing the car, I completely replaced the cooling system (rad/pump/hoses, etc.), full tune up (and lots of other non-germane stuff) and the car has been a very reliable daily driver- always starts and runs fine. Did not smoke at all, oil consumption right at a quart every 3K miles, consistent 16 MPG city.
It does have low compression (@75-80 PSI) and the oil pressure has always been low (@ 10-15PSI at idle (after warmup) and 40-45 PSI above 3K RPM- this is read from an aftermarket gauge, not the stocker).
So, I've been aware that this motor is in need of either a rebuild or replacement (Turbo or V-8?), but need more time to get my ducks in a row.
And, I repeat...the car runs fine, so I was hoping to eke out a few more months before crunch time arrives.
Alright- sorry for the extended exposition...
At the last oil change I decided to see if anything could be done about the low oil pressure and the easiest/first option seemed to be shimming/replacing the e-shaft thermal pellet, which is reputed to be good for an extra 10PSI.
I also opted to use 20w-50 Castrol GTX instead of the 10w-30 previously used.
Well, the oil pressure did increase- dramatically.
From a cold start I was seeing 75-80PSI (it's never read that high) and once warmed up, idle pressure was 25-30 and anything over 2500 RPM showed 60-70 PSI.
This was a completely unexpected magnitude of change.
Unfortunately, there are two bad side effects.
The most troubling is the oil temp which has also increased dramatically.
A few months ago the oil cooler thermostat was replaced, since then the oil temp has mirrored the water temp- pretty steady at @190°F.
Now the oil temp is running about 20° higher, even at low RPM boulevard cruise speeds. Highway speeds raise the temp to 220°F or so.
The oil cooler is hot across the matrix and I have no reason to suspect that it suddenly failed. Water temp has not changed.
Secondly, she's started to smoke noticeably.
Especially bad after sitting at idle (like for a red light), it clears up after a block or so but she never did this before.
It seems logical that the higher oil pressure is stressing the (probably worn) oil control rings/oil seals but we can't figure out why the thermal pellet replacement (from Rotary Aviation, I believe) made such a marked difference (practically doubled the pressure).
It has been suggested -possibly out of desperation- that I dump the 20w-50 and go back to the lighter weight oil, but it seems to me that would cause it to smoke even more, although I could almost live with that if the temp would come down.
Any thoughts/suggestions welcomed.
A rebuild/replacement is not possible at this time, looking for a short term strategy until the right thing can be done.
08-21-08, 11:53 AM
#2
Update:
I retrieved the original stock thermal pellet from the shop and tested it in boiling water.
Nothing happened, so I can confirm that as reason for my previous low pressure (or at least, one reason).
My shop routinely replaces the stock unit with the aftermarket solid pellet when rebuilding and has no history of problems, so we're still at a loss why the oil temp has gone wonky.
We're searching for some stock units- replaced in previous rebuilds- for me to test and will probably try one of those (assuming a good one is found).
I retrieved the original stock thermal pellet from the shop and tested it in boiling water.
Nothing happened, so I can confirm that as reason for my previous low pressure (or at least, one reason).
My shop routinely replaces the stock unit with the aftermarket solid pellet when rebuilding and has no history of problems, so we're still at a loss why the oil temp has gone wonky.
We're searching for some stock units- replaced in previous rebuilds- for me to test and will probably try one of those (assuming a good one is found).
09-09-08, 10:01 AM
#3
Another update:
Situation got weirder.
I found a stock thermal pellet which tested good and we decided to put it in and see what happened.
Well, that's what we wanted to do but the car was having none of that.
The e shaft bolt refused to budge. The first time we worked on it, the bolt zizzed right out...this time it resisted all attempts at removal.
The shop decided that heat was going to be necessary but we didn't have a new seal and o-ring (both of which might be damaged by heat) in stock, so we had to delay while they were ordered.
Naturally, Labor Day slowed everything down so I had some time to think. Meanwhile, the shop suggested I replace the 20w/50 oil with 5w/30...they are big fans of the lighter oil (better for cold starts and mileage, supposedly), so I dumped the brand new oil and used Castrol GTX 5w/30. The smoking issue disappeared but everything else stayed the same.
The main thing I was thinking was WTF is up with this bolt and how badly can things go trying to get it out?
We called Atkins Rotary (supplier of the replacement solid pellet) and they were as mystified as we...it was expected that the oil pressure might increase by maybe 10psi (assuming the stock unit was bad, which mine was)- my oil pressure almost doubled- and it should have no effect on oil temp- mine skyrocketed.
So, while waiting for the seal/o-ring- and hoping to avoid any disastrous outcomes with the recalcitrant bolt- I decided to explore every other possibility.
The obvious first avenue was the oil cooler thermostat- mine had been replaced just a few months ago, but it was a used part so it could be failing again.
This time I decided on a brute force approach and ditched the thermostat altogether and blocked off the bypass hole with a nut and bolt.
It helped- some.
On the highway, all was fine...temps ran parallel to water temp but as soon as speeds slowed down the oil temp climbed to @210° and stayed there.
So now I'm thinking, "OK, the oil cooler is clearly working but maybe the fan isn't pulling enough air at idle".
I was slightly suspicious of my fan's thermoclutch anyway since I couldn't feel a big difference in resistance from cold to hot...it seemed to spin freely all the time.
Naturally, the only clutches I could find locally were S4 units and they wouldn't fit my waterpump nose, so decided to go back to my Taurus efan setup.
This also helped- some.
Now, the temp would drop as expected at stoplights but the oil was still running hotter than I'd like- @200- 205° under light load conditions.
So, now I have a confirmed full flow oil cooler and a fan that pulls well at idle/low speeds (you can feel the airflow from the front of the car) but the temps are still too high, so what's left?
Still trying to avoid potential problems with the eshaft bolt/pellet I decided on a hail Mary shot and dumped the 5w/30 oil and went back to 20w/50.
And... IT WORKED!
Temp spikes at 195-200° under high load/RPMs and drops to 185° (quickly!) at idle/low speed cruise.
Oil pressure is a nice steady 30psi at idle and 60-70 psi above 3k RPM.
No smoking.
At this point, we have no idea WHY any of this happened and frankly, I don't care.
I'm preparing for a 3500 mile trip in October and needed to know if the car was OK...it seems to be but I'm going to make a prerun this weekend- maybe 150-200 miles on the Interstate, just to see what happens.
Sheesh.
Situation got weirder.
I found a stock thermal pellet which tested good and we decided to put it in and see what happened.
Well, that's what we wanted to do but the car was having none of that.
The e shaft bolt refused to budge. The first time we worked on it, the bolt zizzed right out...this time it resisted all attempts at removal.
The shop decided that heat was going to be necessary but we didn't have a new seal and o-ring (both of which might be damaged by heat) in stock, so we had to delay while they were ordered.
Naturally, Labor Day slowed everything down so I had some time to think. Meanwhile, the shop suggested I replace the 20w/50 oil with 5w/30...they are big fans of the lighter oil (better for cold starts and mileage, supposedly), so I dumped the brand new oil and used Castrol GTX 5w/30. The smoking issue disappeared but everything else stayed the same.
The main thing I was thinking was WTF is up with this bolt and how badly can things go trying to get it out?
We called Atkins Rotary (supplier of the replacement solid pellet) and they were as mystified as we...it was expected that the oil pressure might increase by maybe 10psi (assuming the stock unit was bad, which mine was)- my oil pressure almost doubled- and it should have no effect on oil temp- mine skyrocketed.
So, while waiting for the seal/o-ring- and hoping to avoid any disastrous outcomes with the recalcitrant bolt- I decided to explore every other possibility.
The obvious first avenue was the oil cooler thermostat- mine had been replaced just a few months ago, but it was a used part so it could be failing again.
This time I decided on a brute force approach and ditched the thermostat altogether and blocked off the bypass hole with a nut and bolt.
It helped- some.
On the highway, all was fine...temps ran parallel to water temp but as soon as speeds slowed down the oil temp climbed to @210° and stayed there.
So now I'm thinking, "OK, the oil cooler is clearly working but maybe the fan isn't pulling enough air at idle".
I was slightly suspicious of my fan's thermoclutch anyway since I couldn't feel a big difference in resistance from cold to hot...it seemed to spin freely all the time.
Naturally, the only clutches I could find locally were S4 units and they wouldn't fit my waterpump nose, so decided to go back to my Taurus efan setup.
This also helped- some.
Now, the temp would drop as expected at stoplights but the oil was still running hotter than I'd like- @200- 205° under light load conditions.
So, now I have a confirmed full flow oil cooler and a fan that pulls well at idle/low speeds (you can feel the airflow from the front of the car) but the temps are still too high, so what's left?
Still trying to avoid potential problems with the eshaft bolt/pellet I decided on a hail Mary shot and dumped the 5w/30 oil and went back to 20w/50.
And... IT WORKED!
Temp spikes at 195-200° under high load/RPMs and drops to 185° (quickly!) at idle/low speed cruise.
Oil pressure is a nice steady 30psi at idle and 60-70 psi above 3k RPM.
No smoking.
At this point, we have no idea WHY any of this happened and frankly, I don't care.
I'm preparing for a 3500 mile trip in October and needed to know if the car was OK...it seems to be but I'm going to make a prerun this weekend- maybe 150-200 miles on the Interstate, just to see what happens.
Sheesh.
10-03-08, 07:23 AM
#4
I'm updating all my old "issue" threads and this is the last...
I did make a pre-run on the highway and things did not go well.
Oil temp ultimately climbed to @210°F and stayed there.
We had a return to summer-like temps (high 80's, low 90's) and normal traffic driving had the oil temp too high again.
Keep in mind that during this whole ordeal, the car has behaved flawlessly...if I ignore the gauge readings I would never suspect a thing.
At this point I'm considering just removing the gauges altogether- the "ignorance is bliss" approach- but decide to go for a Hail Mary, last ditch move...try different gauges.
I never relly liked the SPI gauges I had...they were cheap but had white faces and the lighting was horrible, so I decided to try some VDO units.
VDO offers a variety of temp sending units and I thought it might be interesting to try the one that replaces the oil pan drain bolt- theoretically the hottest part of the oil circuit. The SPI sensor had been in a Mazdatrix oil pedestal adaptor where it should have seen the coolest temps, being right after the oil cooler.
Parts arrive and are installed- nice black faces and far superior lighting, by the way- and it's off to see what happens.
Water temp readings are consistent with the old SPIs...normally 185°, rising to a bit over 190° under load and falling back at idle. Cooling system seems fine, fan working well.
Oil temp hovers in the 180-190° range (dial resolution not great at this area of the gauge) and in over 300 miles of driving, hasn't broken 195°- ever. Stop and go, highway, mixed- doesn't matter.
Conclusions are hard to draw.
Different gauge, and different sensor location means that a direct comparison is impossible to draw.
I'm considering getting another temp sensor to install in the Mazdatrix adaptor (where the other one was) and toggling between the two...just out of curiosity.
For now I'm inclined to just leave be...I'm seeing temps that seem logical and, absent any other indications that the oil is too hot, don't have a compelling reason to worry.
Since I'm about to embark on a long road trip- the impetus for all this work to begin with- I decided to dump the oil yet again (third time in 5 weeks!- OPEC loves me...) and go back to 10w/30, operating on the premise that fuel consumption may be slightly better.
Temps did not change, so we'll see what happens.
Last year when I made the same trip, I averaged 26MPG over the 3500 miles- it will be interesting to compare results.
I doubt there will be much difference.
On a side note...
When I replaced the gauges, I only got water and oil temp (budget constraints) which left me with a mismatched oil pressure gauge. Since my stock pressure gauge in the cluster is OK I decided to pull the crummy SPI unit out and slip in a VDO clock from a Volvo- it semi-matched the new temp gauges, filled the hole nicely and worked...something my stock clock has never done.
Unfortunately, the clock's lighting is pathetic.
Flustered by my attempts at fixing the cruise control, I decided to detour and see if resoldering the stock clock might work- to my amazement, it did.
Now going on 7 days, working perfectly.
Trecherous bastard will probably flicker and die right after I remove the VDO clock...that's just the way things seem to be going lately.
Sigh.
I did make a pre-run on the highway and things did not go well.
Oil temp ultimately climbed to @210°F and stayed there.
We had a return to summer-like temps (high 80's, low 90's) and normal traffic driving had the oil temp too high again.
Keep in mind that during this whole ordeal, the car has behaved flawlessly...if I ignore the gauge readings I would never suspect a thing.
At this point I'm considering just removing the gauges altogether- the "ignorance is bliss" approach- but decide to go for a Hail Mary, last ditch move...try different gauges.
I never relly liked the SPI gauges I had...they were cheap but had white faces and the lighting was horrible, so I decided to try some VDO units.
VDO offers a variety of temp sending units and I thought it might be interesting to try the one that replaces the oil pan drain bolt- theoretically the hottest part of the oil circuit. The SPI sensor had been in a Mazdatrix oil pedestal adaptor where it should have seen the coolest temps, being right after the oil cooler.
Parts arrive and are installed- nice black faces and far superior lighting, by the way- and it's off to see what happens.
Water temp readings are consistent with the old SPIs...normally 185°, rising to a bit over 190° under load and falling back at idle. Cooling system seems fine, fan working well.
Oil temp hovers in the 180-190° range (dial resolution not great at this area of the gauge) and in over 300 miles of driving, hasn't broken 195°- ever. Stop and go, highway, mixed- doesn't matter.
Conclusions are hard to draw.
Different gauge, and different sensor location means that a direct comparison is impossible to draw.
I'm considering getting another temp sensor to install in the Mazdatrix adaptor (where the other one was) and toggling between the two...just out of curiosity.
For now I'm inclined to just leave be...I'm seeing temps that seem logical and, absent any other indications that the oil is too hot, don't have a compelling reason to worry.
Since I'm about to embark on a long road trip- the impetus for all this work to begin with- I decided to dump the oil yet again (third time in 5 weeks!- OPEC loves me...) and go back to 10w/30, operating on the premise that fuel consumption may be slightly better.
Temps did not change, so we'll see what happens.
Last year when I made the same trip, I averaged 26MPG over the 3500 miles- it will be interesting to compare results.
I doubt there will be much difference.
On a side note...
When I replaced the gauges, I only got water and oil temp (budget constraints) which left me with a mismatched oil pressure gauge. Since my stock pressure gauge in the cluster is OK I decided to pull the crummy SPI unit out and slip in a VDO clock from a Volvo- it semi-matched the new temp gauges, filled the hole nicely and worked...something my stock clock has never done.
Unfortunately, the clock's lighting is pathetic.
Flustered by my attempts at fixing the cruise control, I decided to detour and see if resoldering the stock clock might work- to my amazement, it did.
Now going on 7 days, working perfectly.
Trecherous bastard will probably flicker and die right after I remove the VDO clock...that's just the way things seem to be going lately.
Sigh.
Last edited by clokker; 10-03-08 at 07:26 AM.
10-03-08, 08:27 AM
#5
HAILERS
Join Date: May 2001
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https://www.rx7club.com/showthread.p...IL+TEMPERATURE
You might visit the RETED site.
I've long since removed my sender/gauge. My figures were obviously from a non summer period of time, what with the talk about temps of 80 degrees OAT in the day time.
You might visit the RETED site.
I've long since removed my sender/gauge. My figures were obviously from a non summer period of time, what with the talk about temps of 80 degrees OAT in the day time.
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