JPS SPEEDSTER - with 2.5 Suburu SOHC FI engine - OIL OVERHEATING - Any tips are most welcome!

I owned a Fiber Fab Speedster that the Beck builder's Special edition converted to 2.5L Subaru power and they are Converting my Magnum Dino replica currently. Are you sure the oil is actually running hot, and gauge just isn't faulty?  Maybe Carey Hines of Special Editon will chime in. He knows a lot about the Subaru engine you are running. If the oil is in fact hot as your gauge says he may know the reason. Do you have good oil pressure? If it is actually overheating the coolant temps would probably be running hotter as well because of the built-up heat in the engine. Are the coolant temps running normal. The oil pressure usually drops considerably when overheated as well. If your oil pressure is normal and the coolant temps are normal and you aren't getting smoke out the dip stick tube when you pull the dipstick, or the dipstick feel super-hot to the touch it may not be overheating. In my experience it is many times the simplest answer. I hope you get to the bottom of this. Let us know how it goes. If Carey doesn't post on this thread you may want to PM him. I think is username is Chines. Good luck.

Is the oil temp gauge on the dash still reading oil temp or is it now coolant temp? If it is coolant, and it's not boiling over, could be nothing much.

It could also be a head gasket leak. Ask me how I know.

Agree with Jimmy: check your oil temp with a long candy thermometer that you calibrate to 212F. Just stick it down the dipstick hole. If it's much above 195, the oil's a little hot.

If the oil temp gauge is actually reading antifreeze temp that will be trickier to diagnose.

When Special Edition converted my Speedster to Subaru they did change the oil temp gauge on the replica 356 gauge to coolant temp so in fact you may be running high coolant temps. The standalone fuel management computer JPS uses could be running lean for some reason and cause the engine to run hot also. This would be better than a possible blown head gasket that these engines are known for.  I think JPS uses or did use JDM (Japanese domestic market) used engines in their cars which raises the likely hood of having a blown head gasket as well. Special Edition builds their own Suby engines starting with a brand new warranted short block from Subaru America and uses rebuilt donor heads from the Impreza they buy for each Suby powered car. They powder coat all the engine parts to the color of your choice and use the stock Suby ECU and drive by wire throttle. First class and best in the business.

Well the question is pretty broad because we have no clue how they put the car together from engine, coolant lines, radiator, fans, controls etc.  On top of that we have had guys here who had a miserable time chasing stuff in a subie plumbing but it was in the end user error or rather builder error.   Can you draw something out

I would bet dollars to donuts that your guage is wired up to read water temperature. That's easy to do and it's usually the reading the computer wants to know for engine temp. Setting up a subaru to read oil temperature is harder and short of racing I'm not sure why anyone would bother. So let's work from that assumption for now. You say the temp is high, what is it reading? Does it have degrees on the guage face, or just L and H?

Now that I think of it, I wouldn't be surprised if the water temp sensor was wired up to an oil temp guage (that would be very on brand for JPS) so who knows what the heck you're actually looking at. A sensor/guage mismatch will give you garbage readings.

In any case, the cooling set up on a subaru conversion needs to have the air bled out of the system. With the low front radiator and the possibiity of high spots in the hose runs, these air pockets are easy to get, hard to fix, and bad for cooling. Step one is making sure that is done. I don't know exactly how yours is plumbed, so I can't give you a step by step. Look for the high points in the system. You can burp them sometimes by squeezing the hoses and working the air towards the bleed point. I'd start there and see if that helped.

i concur with the comments here ...the oil temp is most ;likely the water temp on Dr. Jekyll's subaru car's.....i advise locating  a good mechanic /experienced HOT ROD GUY in your area and have him go from stem to stern and check all the possible short cuts done by the madman Mr Hyde....i advise a good set of autometer gauges oil/temp/volts and learn the SR-71 or U2 3 second rule to monitor the vital signs....as well as your shifter....remove the shifter and check the shift rod ball socket...that SOB left a 50 yr old worn out part in my $40K car!...a huge job to replace since a radiator is in the way...then put a EV4Unow.com  composite bushing in the hanger and check the trans coupler as well  @gemcc1  my dealing with that man is well documented here if you care to do a search....DM me if you want further details

I will agree to how easy it is to have air in the coolant system on a Suby/speedster. I had to change my thermostat housing and liked to never get the air out of the system. I wound up adding a couple of Prestone coolant fill gizmos in a couple of spots to get the job done. The air pockets fill with super-heated steam and can overheat the engine and do great damage when they arrive and stay in the block. Before installing the extra fill points, I tried everything including having the front of the car jacked up so high it almost looked like it was hanging from the rafters. Still no joy. The great thing about running the stock ECU is that I could monitor all the temps the ECU followed with scan gauge plugged into the stock port that all modern cars have. The Special Editon Suby cars can be worked on by any Subaru mechanic or dealership service dept. if need be. My car stopped running almost 18 months after Special Edition converted it and they sent Mike their main engine guy to my house, and I live 4 hours away. Turned out to be a faulty power connector. Now that is Service. They calibrate the oil temp gauge in the replica multi gauge to read water temp., but it is still a yes or no idiot type gauge. That is why I ran a scan gauge with blue tooth that displayed all the ECU read outs on my phone when I wanted to. This gave me actual temps. in real time. I have heard more than a few people that have had bad experiences with JPS cars and got little to no assistance from JPS. I hope your situation is not too hard to straighten out.

oil in my Por runs around 200-215,,,if it gets to 226 I put the car in "sport" and it drops back to 198 range..

JPS does not use factory ECUs. And Jimmy, I remember filling the cooling system and bleeding it in my Vanagon. I believe the front had to be raised a minimum of 14" or something like that. There was a bleeder at the top of the front radiator and another bleeder in the engine compartment.

But these custom cars are NOT that. You need to come up with your own procedure and YES GET THE AIR pockets out, they will kill the motor.

Just a question because I'm curious. We evacuate refrigeration systems. Would drawing a vacuum on the cooling system and then filling into the vacuum help get the air out?

Yep.

@Stan Galat posted:

Just a question because I'm curious. We evacuate refrigeration systems. Would drawing a vacuum on the cooling system and then filling into the vacuum help get the air out?

Refrigeration systems are "evacuated" via a vacuum pump to boil/remove the moisture, not to assist in filling with refrigerant.  

But perhaps as you suggested, using vacuum to "suck" in the coolant may prevent air pockets in an automotive cooling system.

Jason

@JasonC posted:

Refrigeration systems are "evacuated" via a vacuum pump to boil/remove the moisture, not to assist in filling with refrigerant.  

But perhaps as you suggested, using vacuum to "suck" in the coolant may prevent air pockets in an automotive cooling system.

Jason

I've made a life in commercial HVAC service for the last 40 years as a union steamfitter and owned my own supermarket refrigeration service business for the last 26 of them. I'm pretty sure I understand why we do it.

I didn't think it was such a dumb question - but then again, I'm not the smartest guy in the room. It seems like pulling a vacuum on the cooling system would draw coolant into every corner of the system - but since I'm just an ape with a keyboard, I'll go back to eating my crayons and leave you to it.

I remember Carey mentioning making use of a vacuum at one point but I think they made the routing of the hoses more amenable to gravity aeration.

In my case I have aircraft or rather pressure welded tubing and there are drains or venting valves at the four wheel wells and the two radiators.  I also use Evans cooling because I asked myself if I ever wanted to visit this again and again and the answer was no!   Then I had an overflow tank to the overflow tank done to contain the fluid for boil over at stopping of the engine made which has totally eliminated my issues with heat and gurgling over at engine stoppage.  

Some people actually have a circulation pump continue till the temp goes down I have not needed it. ADDING a Engine Guard cylinder head and tranny temp is valuable knowledge as well.

@Stan Galat posted:

It seems like pulling a vacuum on the cooling system would draw coolant into every corner of the system

Absolutely, if you could pull a vacuum it would fill the system. The possible difference that AC hoses and parts are designed to regularly contain a vacuum as well as hundreds of pounds of pressure.

I have some doubts that a regular antifreeze cooling system would do well being pulled to a vacuum. My bet is that the radiator would hold up just fine, but that the hoses would collapse pretty quickly. Perhaps they wouldn't totally seal as they collapsed and you could still pull a vacuum.

Only two ways to find out, ask Bing's AI persona... or try it .

I just saw Ray's description of his system. That looks like it would handle a vacuum.

@Michael Pickett posted:

Absolutely, if you could pull a vacuum it would fill the system. The possible difference that AC hoses and parts are designed to regularly contain a vacuum as well as hundreds of pounds of pressure.

I have some doubts that a regular antifreeze cooling system would do well being pulled to a vacuum. My bet is that the radiator would hold up just fine, but that the hoses would collapse pretty quickly. Perhaps they wouldn't totally seal as they collapsed and you could still pull a vacuum.

Only two ways to find out, ask Bing's AI persona... or try it .

_{(... munching Crayolas...)}

Yeah - the hoses.

I clearly hadn't thought about that when I was asking my dumb question.

I wasn't thinking of drawing a vacuum into the micron range, just 25" or so to draw the coolant into the corners and crevices. I had wondered about how the cap would do with the pressure relief having a vacuum pulled on it rather than pressure applied to it (I'm 99% sure it'd be good) - but I can guarantee the radiator would be fine since a micro-channel condenser is built exactly like an aluminum radiator, by the same manufacturer (in point of fact).

Still, the larger radiator hoses would collapse for sure under even a mild vacuum, so you'd probably only be able to pull it to 10" or so.

... but what do I know?

_{(... back to munching Crayolas...)}

Why should we trust the observations of a guy who has dealt with systems like this his whole life? Let's go to the real fount of knowledge: Microsoft Bing powered by ChatGPT.

Fun, in a creepy kind of way.

My overachieving, Type A (+++), hyper-educated, fun, pretty, crazy smart daughter _{(who doesn't eat crayons)} sometimes runs her texts through ChatGPT to make sure she's not being too abrupt or unreasonable with slower people.

My other, more laid back, but equally beautiful and intelligent daughter _{(who also doesn't eat crayons)} points out that she's using a machine to help her be more human.

As per usual ChatGPT is eerily spot-on.

Regarding exposing the pump to coolant,even I know more than that. I have to buy my tools, so wrecking them by stupidity or negligence was not the game-plan.

If I were doing it (and I'm not going to because I'm a shaved primate, and therefore deeply committed to the primitive air-cooled life), I'd draw the vacuum on a tank with two valves and connection points (a refrigerant recovery cylinder, for example), and then connect the other tap on the tank to the cooling system.

I'd then draw coolant into the system from a dip-tube in a drum with enough capacity that I could ensure the system would not suck any air. Once coolant started running into the cylinder with the pump connected, I'd break the vacuum (by disconnecting the pump from the recovery cylinder) and see where I was.

@Stan Galat posted:

My overachieving, Type A (+++), hyper-educated, fun, pretty, crazy smart daughter _{(who doesn't eat crayons)} sometimes runs her texts through ChatGPT to make sure she's not being too abrupt or unreasonable with slower people.

My other, more laid back, but equally intelligent daughter _{(who also doesn't eat crayons)} points out that she's using a machine to help her be more human.

That made me laugh Stan, we could have a few laughs comparing stories about our kids

@IaM-Ray posted:

That made me laugh Stan, we could have a few laughs comparing stories

We should get together over a box of Crayolas!

Yes, we use airlift coolant vacuum system and it gets the system 90-95% filled but we still have to burp a little air.  We do the same as Boxster and lift the ends of the car forcing them to be the high point, plus we also have a air bleed in the crossover.

As for the OP question: you need to find out what sending unit you have (120c or 150c) and if it is showing oil or coolant temps.  I would suggest taking some measurements on your motor as well, so you can correlate actually figures with the unnumbered gauge.  For coolant you should be running the 190-210 range, and on a genuine VDO gauge using a 150C sender, 1/2 way is 190.

Would springs inside the radiator hoses help with the collapsing?

(This guy is over here eating lead paint, tastes better than crayons)

@DannyP posted:

(This guy is over here eating lead paint, tastes better than crayons)

You're eating paint chips? Any salsa to go with that? I'll be right over with some Tide pods and airplane glue.

P.S.:

Do the crayons affect your refrigeration knowledge? Asking for a friend...

Too many crayons and you'll start to wax poetic.  Your language may also become disturbingly colorful.

@JMM (Michael) posted:

So that's where that 10mm got to!