andernamen

iTrader: (2)

GSL-SE with 210,000 miles - recently put another engine in the car that has some issues, I was so desperate for a running engine, I didn't fully check this one out. Low compression on rear rotor and, I think, some type of oil leak INTO the coolant. The car has the original radiator that admittedly was causing cooling issues with the previous motor. I took it to a radiator shop and they did a vibrasonic cleaning in a solution tank, and said it should be good. New aftermarket water pump. Fan clutch is working fine. New thermostat. At low speeds the temp tends to hover just above 1/3 of the way from cold. As soon as I get on the interstate, it jumps up between 1/2 and 3/4. Slow down, temp goes down. If I remove the A/C condenser, would this help? What should I do next?

DriveFast7

iTrader: (1)

removing the ac condenser would help especially if it's fins are all bent and blocking flow

did you chemical flush the engine cooling system too?

andernamen

iTrader: (2)

No

82transam

iTrader: (18)

I would flush the whole system, it's cheap and relatively easy- just a little messy. If you're up to spend a few bucks it might be worth buying a new radiator. Rockauto has them pretty cheap and they work very well.

Do you have a way to get actual temp readings? That would help greatly since the stock gauge is less than ideal. I run a T2 engine with A/C and even on hot days (90's are about as hot as we get typically) I rarely get over 200-210 degrees...

Rotaries rely heavily on oil cooling to keep temps in check, what shape is your oil cooler in?

I'm concerned that you suspect oil is getting into the coolant...

t_g_farrell

iTrader: (1)

Oil in the coolant is a new one on me. I thought with rotaries its very hard for the oil to mix with
the coolant unlike a piston engine with head gaskets and all.

Make sure the oil cooler and the lines are good. New oil cooler lines can help a lot sometimes.

andernamen

iTrader: (2)

The oil cooler is bent, but doesnt leak. How can i check it?

t_g_farrell

iTrader: (1)

Take it to a radiator place and have them leak test it and see how it flows. Not sure
what the flow rate should be speced at.

KansasCityREPU

iTrader: (9)

If you do take the FMOC to a radiator shop, make sure to take out the internal thermostat first.

82transam

iTrader: (18)

Yeah same here, it's usually the other way around. You get coolant in the oil when the o-rings start to fail...

Personally I would suggest getting some gauges (even just some cheap ones) that will let you monitor both the coolant and oil temps with real numbers. I realize it's not a 5 minute job to install, but it would give you a real good idea of what you're dealing with.

A cheaper, albeit more annoying option is to get one of those cheapo laser thermometers that harbor freight sells and once the car is getting hot (or hot according to your stock gauge) pull over and take a few readings, specifically off the back of the water pump housing for the water temp, and for oil temp you can try to get a reading off the oil filter pedastal or the short oil cooler line that comes off the front cover.

I've had some pretty shitty bent up oil coolers over the years and they still seem to do a decent job of cooling oddly enough, but like Repu said, pull that t-stat out before you bring it anywhere since they might not realize it's there... good luck!

rx7lives

Yeah, that's a weird one, the only thing I can think is the outside o-ring is leaking on the bottom of the engine right where the oil pan is.

Low compression on one rotor is bad, did all three lobes have appx. the same reading?

I had a 12a that I flushed out and then when I started it, it did the old start on one rotor and then once the water was pushed out, the other rotor kicked in. I think the flush pushed the inner o-ring into the combustion chamber a bit. In fact the motor was locked or at least it would turn with the starter the next day. I turned it backwards and got all the water to go out the exhaust port (drain coolant before you do this). Since the engine was toast and it was crap engine anyway, I put some gas down the thermostat hole hoping it would expand the seal, the only issue is if it expanded it too far, no chance then.

Drained the gas, started it with no coolant and then let it run with the cap off until I saw water flowing. Put the cap on and it actually drove like it always did but the temp gauge went to over the 3/4 mark. Oh well, I figured, I'd drive it to my house (17 miles away) and do the engine swap there. The coolant stayed in the same range and it ran fine. I was so disgusted I tried to see what would happen if I floored it in neutral (don't do this, if the rotor grenades and takes out the chamber you could cause some serious injuries). Funny thing is, it never skipped a beat.

When I replace the motor, the salvage yard motor I put in it was the best 12a I've ever driven, man I wish I hadn't sold that car. It took 2 1/2 hours from hood up to hood down to swap engines, a personal record which was destroyed when I spent my entire youth trying to get out a pilot bearing out of a 13b engine. Finally came. I bought Mazdatrix's tool and it's worth twice what they ask, my pilot bearing on the same 13b (this was a clutch change) was, if anything, worse off. The tool removed it in less than a minute. I also bought the pilot bearing driver that drove the bearing in so far, the seal fit perfectly.

DriveFast7

iTrader: (1)

Ask them if they flush it with hot fluid, they usually do. I take mine to an ultrasonic cleaning shop and confirmed they push hot fluid thru it. FOr the thermostat to cycle.

andernamen

iTrader: (2)

Checked temps with a laser thermometer and found idling highest temp to be 184 around thermostat housing area. Highest oil temp around 165. All external readings after short period of driving. Gauge read little more than a third of the way up. Im beginning to question the gauge reading, but i have to get it on the interstate to check.

82transam

iTrader: (18)

Decent temps so far at least

88GTU_AutoX

iTrader: (1)

Hey guise, just hopping on in, here.

I have cooling issues as well, though I nearly never see them unless I'm autocrossing, in which case my temps get up to halfway in under a minute of hard driving. I'm debating a new rad, but I hadn't yet heard about the importance of a good, functional oil cooler on top of that.

I've flushed, back-flushed, changed tstats, replaced a blown hose, and used KeepCool and the temps won't stay down. I want something that I'd actually be able to track, and if it's getting from 1/8 above cold to 1/2 in a minute, it won't be able to take multiple laps on-track.

Also, I've never heard of oil in the coolant either, but you may want to make sure that it isn't going the other way around as well...

andernamen

iTrader: (2)

I'm rethinking oil in the coolant. I have flushed a few times now and haven't seen a sheen in the coolant. May have been left over crap in the engine or lines. I will keep an eye on the temps and if they stay relatively low I guess I'll replace the sensor. It is on the bottom left, correct?

82transam

iTrader: (18)

The sensor for the stock temp gauge you mean? It's the small bullet looking one on the rear iron of the engine kinda near the heater hose outlet and under the big oil pressure sensor.

88GTU_AutoX - If you are tracking the car you should really consider getting some real gauges instead of relying on the stock ones. And yeah the oil cooler is basically just as important on a Rotary as the radiator is for keeping things cool

From personal experience I can tell you guys that at 25+ years old the stock gauges are a guideline only. The FC I had would get to about halfway on the gauge after warming up but never move after that no matter how hot/cold etc the engine got - basically useless. On my T2 FB is a similar problem, the gauge gets to warmed up (1/4 of the way up on an 83) but won't go any higher unless the temp has increased dramatically - like it is has to go up ~20 degrees before that thing will move again at which point it climbs quickly.

88GTU_AutoX

iTrader: (1)

Bahahaha... I'll invest very soon then. Thanks. Is it just the gauge that needs replaced? or the sensor as well? I've never messed with swapping gauges before.

Thanks for the prior experience, btw.

88GTU_AutoX

iTrader: (1)

^^^ Don't answer that. I was feeling rather incompetent. How about: what size adapter is needed for a mechanical gauge on an FC?

82transam

iTrader: (18)

I've been using electrical gauges and just drill and tap a hole in the back of the water pump housing near the ECU's water temp sensor. I'm not sure what would be needed to put an aftermarket sender in the stock gauges sender location on the rear iron, although I'm sure someone has probably done it.
As for the stock gauge accuracy I'm not really sure if its the sender or the gauge, or both lol I've never really messed around with trying to fix them - like I said i just use them as a general suggestion lol

On a side note, I'm surprised no one has come in and argued with me about this. Whenever questions like this come up there's always someone that comes to the stock gauges rescue...

88GTU_AutoX

iTrader: (1)

Then I'll do that. I read up yesterday that the s4 temp gauge was FAR superior to the s5 gauge. Mine is obviously an s4 (by my username), so I'm thinking that it is likely pretty accurate. The argument is usually that the s5 gauge is clearly nonlinear, whereas the s4 gauge is accurate AND linear. My temps are always very predictable as well--from idle, 1/8 above cold line, from normal driving, almost 1/4 above cold line, and after a 1 minute autox run, nearly 1/2.

I'm still trying to eliminate possibilities, so I know that isn't low on coolant, it doesn't have a bubble and it isn't leaking. The fan clutch doesn't make sense, as I'm usually moving fast enough in autox to not need it at all.

So the possibilities are dwindling. the water pump isn't a gradual thing, so that's out. The rad doesn't look bent, though I will check for hot and cold spots when I get back home. The t-stat is only 5 months old, and the problem existed beforehand. I AM missing a section of the foam that sits under the rad to seal the air passageway and direct air through the rad. I'm not sure how much of a problem this is.

gahhh... This is driving me up the wall, as I've been wanting to spend some money on a track day, but I know my car wouldn't make it through in one piece...

andernamen

iTrader: (2)

Hot yesterday 90+. Put the car on the interstate and the temp gauge was well over half way up, but not all the way to hot. Stopped the car to take readings but kept the engine running. Highest temp I could find was 202 around the thermostat. The lower radiator on the left was about 180, and on the right about 10 degrees cooler. The oil cooler was around 165. I don't want to put too much stock in these temps, but I do think the sensor is probably bad.

82transam

iTrader: (18)

202 is well within the safe zone and 165 on oil is perfect if not even a bit on the cool side!

KansasCityREPU

iTrader: (9)

Here's how I put my electrical gauge sensor in. I used an old school water neck. I tapped it with a 1/8 NPT.

82transam

iTrader: (18)

^That works!