Rad exploded, now won't start. O-rings and compression fine. s5 NA
 

We had an overnight super deep freeze a while back. The next morning I was driving to work and the temps took off and then top of the rad exploded. Moments later the car snuffed. I had to tow her home. The rad has been replaced. The car cranks just fine but she won't catch. I finally had time to dig into her today.


No blown fuses that I can find. Battery fulled charged.

Cranked the car with the rad cap off. No geysering, no visible activity at all from the inlet. Coolant level unchanged after cranking. So the o-rings are okay.

Did part one of the poor-man's compression test. Just over 90 on both 1 and 2.

Tied L1's plug to the strut bar and cranked it. Saw lots of spark, but it looked a little weak. More on that in a sec.

*Almost* pulled the fuel line off between the filter and the rat's nest - a little spurted out. So there's pressure in the line.

Pulled L1's plug after three short cranking attempts, including a crank with the fuel cut. Plug smelled slightly of gas but was completely dry.

12v between the batt and the EGR solenoids.

Weak spark - I checked voltage on coil 1. Between the either nut under the black plastic cover and the battery's neg terminal gets 12v. BUT when checking B/Y on the coil's white plug I get ~6.5v. I've cleaned the coil's grounds and re-checked and still got ~6.5v. Gonna swap in another leading coil tomorrow.

I've been associating the engine's snuffing with the rad blowing. I assumed something got hit by that blast/bolt of coolant that caused the engine to shut down. At this point the culprits are air, fuel or a big, fat vacuum leak. I'm iffy on blaming spark and am wondering if the coil wasn't weak before the incident. I did a quick once-over and didn't find anything that would have been a major air leak - visible vac hoses seemed fine as did the intake snorkel et al.

Tomorrow I'm going to check power to the injectors and try to further confirm that fuel is really getting into the engine. I don't think the plug should have been as dry as it was.

Comments welcome. :)

check the CAS and see if it has been soaked.
one thing that you could try is to get a hair dryer and go over all the wiring,and try to get it "dry".It won't completely take off coolant but it will help.

Good idea. :)


I think that's going in the wrong direction. I don't want spend hours standing over the engine bay in sub-zero weather with a hair dryer. I think the key to this is to use troubleshooting to isolate the source of the problem. I don't have any evidence yet to suggest that coolant on the wiring is responsible and I won't focus on that until I do.

I'm going to look again for vac leaks when the sun's up, and then focus on fuel delivery until that's either borne fruit or is off the list. :)

Did you make sure it's not flooded? In the cold temperatures, even piston engines are hard to deflood if they do get flooded. Only way is to use heat to make sure all the fuel evaporates...

Maybe when the rad exploded, coolant got sucked into the intake snorkle and into the engine?

In the course of working on it this afternoon I pulled both plugs, in part to re-apply anti-sieze to them. Both were bone dry. I wpied their ends on a rag and they didn't even leave black marks behind. It would be the driest flooding I've ever seen. ;)


The air intake (I'm using a K&N) was directly shielded by a custom airbox, as well as by the rad's upper hose neck. The explosion happened roughly where the red line is below, except it was a stock rad (it's strangely hard to find a pic of one of those online.) There are puddles of coolant on top of the engine, and traces on the wiring and piping on the passenger side of the engine. The battery, p/s pump and everything behind it went untouched by the blast. I'd say the air pump, the alternator and the front of the UIM got the worst of it.


https://www.rx7club.com/attachment.p...1&d=1264224975

OIL in the spark plugs holes... unless you have verified no fuel, checked the pressure?? and what about the coil, any change when you replaced it?

I had oil on hand when I did the compression test. Didn't use it when I got the strong returns.

I've sort-of confirmed that there is pressure between the filter and the rails. I'll be checking tomorrow that the injectors are getting power. Checking the CAS as suggested will be part of that.

Coil hasn't been replaced. It's cold and dark out there now. :chicken:

pressure wash it and blow it with compressed air. there is probably coolant in everything so unplug and dry out all the connectors.

No pressure washer nor compressed air where the car is parked. Plus there's the whole icing up and freezing issue (possibly inflicting new damage) for any water I fail to clear away.

then my only suggestion is wait for spring or get it somewhere where you can work on it.

coolant and electrical do not mix.

Replaced the leading coil, it metered like the old one and the car didn't start. Curious part - if I meter between the connectors I get ~6.5v. If I go from b/y to ground I get 12v. Where's ma 6v goin'?

Key on, pulled a secondary injector connector and got 12v.

Started to pull the CAS, unit wouldn't budge and I don't want to pound on it. I'm leaving it alone for now.

I sprayed several shots of Quick Start into the UIM and then cranked her. She fired right up and ran for about 7 or so seconds. I was able to rev her repeatedly during this. So I'm going to continue to pursue fuel as a cause. I'm going to dig down to the primary injectors and see what I find. Right now I'm thinking either voltage isn't getting to them, or there's some ice or a frozen line or something preventing flow. We'll see. :)

Standard diagnosis. Check AFM, injectors and spark. Remove the manifolds, secure injectors to rails via zipties, remove CAS, key ON, turn the CAS gear and observe the injectors. You may get lucky with guessing but keep this as a last resort. And breaking the CAS is nearly impossible, its metal.

sounds alot like the AFM is not powering the fuel pump, can you do a voltage test on the pump? You could also try jumping the intial set connector so that the pump runs without the key in the start position. which you will have to do anyways to follow the cas turning instructions above.

Manifolds are ready to come off. Came back to get a fresh battery for my mp3 player. :D


I will be doing this with the primaries if I can't find anything else down there.


It still has electronic and plastic bits inside. I'm going to use a spare for the injector testing above.


Just checked it. Disconnected the fuel line between the filter and the piping to the rails. Put the hose end into a jar and cranked her - jar is now half full of gas. Fuel pump is working properly and fuel is getting to the rails. :)

Dammit. :(

The primaries seem to be fine. Both are happily clicking away when the CAS is spun. I didn't actually pull them, though. I left them in and listened, and then did the poor-man's stethoscope by using a screwdriver pressed to my ear. The only thing I haven't done is actually watched if they're releasing fuel. It's gonna be a pain, but I think that's next.

I was surprised to find that there wasn't any coolant pooled in that low area where the primaries sit. The coolant didn't get down there at all.

12v on the b/w for the rear's primary. Jumped right to the CAS test without checking the front's voltage.

It's looking a lot like fuel delivery is a-ok. When everything's back together I'll try cranking with the AFM disconnected. Other than that, this looks like it's back to either spark or compression for a cause. Which brings me back to:

https://www.rx7club.com/attachment.p...1&d=1264277607

When I did that test I got ~6.5v. And yet I also found that 12v was being sent to the coil... :scratch:

Could this low voltage at the leading coil be the result of a failure of the condensor connected to B1-09? Or should I turn my attention to the g/y wire and the ecu?


https://www.rx7club.com/attachment.p...1&d=1264281144

Honestly, the wiring is pretty good at keeping water out, I usually wash the engine bay with no problems, (but it could be possible i suppose)... have you tried starting it with oil in the plug holes, crank over for 15-30 seconds with the EFI fuse out and spark plugs out and gas pedal down all the way to the floor. Then put the plugs and fuse back in and crank it over without stepping on gas pedal? If it tries to start like sputtering, then keep trying this until it starts....

On the other hand, one more thing you should check is the water thermo-sensor located on the water-pump itself. I believe this guy will give you hard starts if it's failed...

You have fuel, you have spark, you have air.... It should start with all those conditions met and the only thing that happed before was the rad exploded.... I would also worry as to why the radiator exploded, did it freeze? If so, it could cause metal to crack. Did it have an extreme pressure causing it to pop? This would be bad for seals...

I really want to emphasize that just a tiny flood in cold weather will make a car not start. I had a friend the other day tell me he was called to help start a car, it turns out it was flooded, it was cold here and there was no way he was able to start and unflood it. He tried removing spark plug, cranking without fuel. Nothing worked. He ended up using a blow dryer directed at the cylinders. It started right up after that....

Okay, the primary injectors check out. Fuel delivery is off the list. I put everything back together and came in without trying a start with the AFM disconnected. I'm cold, hungry and I didn't have a light. Maybe later tonight, tomorrow for sure.


Me, too.


I'm well aquainted with the deflooding procedure. It's on my to-do list if I keep coming up empty handed elsewhere.


I broke this on a past RX-7 several winters ago. I can assure you that it makes starting impossible in sub-zero temperatures. I looked at the sensor this afternoon and it was intact. I may test it later.


Apparently my coolant mixture was weak enough for it to at least turn slushy. After the explosion I pulled off the road and went to add water. When I took the rad cap off it was all slush beneath. I had been adding small amounts of straight water early in the fall as I was chasing a leak where I'd piped the temp sensor for my rad fan into the upper rad hose. I'd expected that 3 or so months would be more than enough time for that straight water to become intermixed.

What I think happened was the mixture in the rad was somewhere between slushy and frozen when I drove off, on my way to work. The coolant couldn't circulate. Shortly before the explosion my digital temp gauge started flashing (it does this once it hits 210F.) The last I looked at it, moments before the explosion, it was at 216F. Then steam was pouring out from under the hood and then the car snuffed. The stock gauge never left 1/2, btw.

I've intentionally overheated an s4 NA (H on the stock gauge, no aftermarket gauge at the time so no idea as to the true temp) in the course of doing RETed's modified coolant flush with no apparent harm done. While 216F is nothing to smile about, I'm certain it's well away from being damaging.

Up until I did the compression test yesterday I was worried that the o-rings might have also blown out. The rad may have blown, but that didn't mean it was the only failure due to coolant pressure. I still don't know for certain that there isn't heat-related damage within the engine, but after the last two days it my feeling is that it's unlikely.


I hear ya. If it does come to using oil, we'll see what we get. :)

check the water temp sensor behind the water outlet. If its not working you wont get enough fuel to start in cold temperatures

This afternoon:

- went out cranked her after last night, AFM disconnected. No change.

- changed the noted condensor out for another. No change.

- checked both plugs after these attempts. Dry.

I haven't pulled the water thermosensor yet. When I broke the one I mentioned before, it still started in weather like this, albeit it took longer to fire up than normal. It wasn't until a morning when the temp was down around 5F that she completely refused to start.

I'm split right now between trying oil and pulling the thermosensor. I've got about 45 mins of daylight left and it's been raining out all day. Whichever one I choose will probably be the last thing for today.

That 6.5v on the leading coil is still bothering me. If the spark's at half the strength it should be at, maybe that's the problem right there. If the coil and the condensor are both okay, then that leaves the ECU, which I won't pull until the rain stops.

Did the car stall/die itself after it overheated? I'm guessing your 'poor man' test was to just use a piston checker collectively? At this point (and probably the first thing I'd have done, at all), I'd pull the two leading plugs, and turn the engine over by hand (19mm socket on the front e-shaft bolt), every half rotation should should hear a pulse from each rotor, and it should alternate from front to back every turn. Go around 3 times to check all faces. That'll let you know if at least all 3 faces are producing compression. If all of them sound even and decently strong, pull your EGI fuses and crank the shit out of the car in intervals, let it sit, repeat. Plug it back in, have someone crank with it at WOT and spray as much starting fluid as you can find into the intake, you should at least get some kind of attempt to fire.

I put some 5w30 into the engine. No change. :(

I'm beginning my search for a replacement coil. New forum searching today has found several posts stating the car will run even if it's only using the trailing coils. If that's true, then spark probably isn't an issue.

- not spark
- not fuel

leaving me with

- air
- compression

The butterfly linkages on the uim all seemed fine. I think I'll give them a closer look. I'll do another compression test as well, and see if I can't grab someone to do the cranking for Poor Man's part 2. :)


Yup, can't hold the valve open and crank the engine at the same time.


I did this by hand, pulling on the ps/ belt, after adding the 5w30. I could feel the resistance with each pulse, hear the whoosh and see the ripples in the oil that had dribbled out from the spark plug holes. I was doing this to spread the oil before it had time for much to dribble back out of the holes (some did anyway.) I did not watch it in that detail, though. Something for tomorrow. :)


There is already a fuel pump kill switch installed. Using it has made no difference.

As mentioned earlier, she fires right up with Quick Start.

https://www.rx7club.com/showpost.php...0&postcount=11

But since just about anything will run with Quick Start, this doesn't help much.

The car will start and DIE with the AFM Disconnected.(at least my s4 does.)
connect the AFM and try a shot of Ether in it,.
If everything is Ok,it will fire up and keep running.

The only things really left, given the above, is the quantity and time that they're introduced. So, it could be either an extremely large vacuum leak, lack of compression, or the time either the injectors or plugs fire.

The only downside I can see here is that usually trying to pull or turn by hand without some better leverage means it turns over slowly so you can't really get a good idea of the strength of the pulses. Try again tomorrow so you can get a good bit of a crank on it to better compare the sound.



Didn't see the quickstart mentioned, and usually I pull the EGI simply to avoid firing the gas that's still in the champer (so the plugs don't fire with the leadings out). My guess is something introduced a large vacuum leak, or you've got too little compression. If you can find a volunteer, try to modulate your AFM flapper by hand while cranking and see if you can get it to kick over or even start. Usually the quickstart will get it runnnig roughly enough to stay running with large throttle input or give you an idea of some other problem.

The last resort---

*Not Generally Recommended*
Pull the car to about 20 mph, let the clutch out, you should get the engine up to the 3000 to 4000 Rpm range. This is assuming it's really flooded, or low compression. i've had a few blown motors(too low comp) start with this way ONLY.