Burning coolant - need opinions

[Raphial]

Hello, I've got 1995 E420. I've had it for some time now, and recently had to rebuild the throttle body (that was fun), some maintenance, and had to rebuild the fuel rail.

When I pulled the fuel rail turned out two of the injector caps were missing, and the injectors RTV'd in place. Thinking the caps popped off and fell into the valves, I went ahead and pulled the intake manifold whole. Rebuilt the entire fuel rail, cleaned up the intake really good (hadn't been serviced in many years) and put it all back in. I put a thin coating of black RTV around the coolant ports, being conservative about how thick of a coating there would be. Turned out the caps were just missing, someone never got new ones.

For context I've built many engines, and have a lot of experience with classic cars and custom rigs.

However after putting everything back together the car runs but is burning coolant from somewhere. I presume the intake gasket. No misfire, runs normal, idles down, etc but has a ton of white smoke when I fill up the coolant. It's obviously burning.

I've replaced this intake gasket twice now and it still burns. I'm ripping my hair out at this point as I have to wait for these gasket sets to mail in, and I need this car out.

Is there something I'm possibly missing? I properly torqued down the intake and in sequence after waiting one hour for the RTV to set after being only snugged down. I've never ran into this before.

Head gaskets are fine. Compression is fine. Misfiring and coolant burning was not a problem before removing the intake manifold.

Any opinions would be great, thanks

 

[gsxr]

I wouldn't jump to conclusions that it's burning coolant just yet. Are you losing coolant? Can you pressure test the cooling system and see if you lose both pressure and coolant during the test?

RTV should not be needed on new gaskets and isn't recommended, but also should not cause a problem either. Make sure to fill the block via the upper radiator hose, and/or use a vacuum fill tool, to avoid air pockets. The cooling system isn't happy if you only fill it from the plastic reservoir.

 

[Raphial]

I wouldn't jump to conclusions that it's burning coolant just yet. Are you losing coolant? Can you pressure test the cooling system and see if you lose both pressure and coolant during the test?

RTV should not be needed on new gaskets and isn't recommended, but also should not cause a problem either. Make sure to fill the block via the upper radiator hose, and/or use a vacuum fill tool, to avoid air pockets. The cooling system isn't happy if you only fill it from the plastic reservoir.

If I run the car for a few seconds before refilling the coolant, it idles without smoking much. Maybe a tiny bit. I add coolant then it starts to bellow out white smoke. Like burning ATF fluid through the valves.

I don't have the equipment to pressure test the coolant system, I'm gonna see if a parts store can lend me it.

Otherwise it runs fine. I had a hunch it could be running coolant through the EGR port (coolant and EGR port are close together in the front corner of the passenger head) but doesn't seem to be the case.

Just to humor the idea.. what else could suddenly be burning white smoke if not coolant? Some coolant did get into valves when I removed the intake manifold. I thought it could just be burning out but I drove it around the block the first time and it still smokes.

 

[Raphial]

I wouldn't jump to conclusions that it's burning coolant just yet. Are you losing coolant? Can you pressure test the cooling system and see if you lose both pressure and coolant during the test?

RTV should not be needed on new gaskets and isn't recommended, but also should not cause a problem either. Make sure to fill the block via the upper radiator hose, and/or use a vacuum fill tool, to avoid air pockets. The cooling system isn't happy if you only fill it from the plastic reservoir.

I haven't ran it long enough to see if it's losing coolant for sure but I'll let it idle for a minute and check.

 

[TerryA]

I had a 67 230 Finn Tail that had a bad brake booster check valve to the vacuum system. When I stepped on the brakes white smoke billowed out of the exhaust.

Have you disconnected or changed any vacuum hoses? Possibly reversing a check valve somewhere.

Just a thought

 

[Raphial]

I had a 67 230 Finn Tail that had a bad brake booster check valve to the vacuum system. When I stepped on the brakes white smoke billowed out of the exhaust.

Have you disconnected or changed any vacuum hoses? Possibly reversing a check valve somewhere.

Just a thought

That's a good thing to check, good call. I have all of the vacuum hoses as they are in the service manual diagrams, and I'm usually pretty good about hooking them back up where they belong (I'm used to lots of vacuum lines on the cars I work on).

So I did confirm the coolant did go down and I believe it is burning out. I ran the car for five minutes and it started to get up to temp before I shut it off. The idle started to periodically dip and go back up after it warmed up, but I'm sure that's because of the burning issue. Normally it would run fine.

It did idle down to about 6-700rpm, but held a steady 1000rpm on start up for 10-15 seconds.

I also checked compression on all cylinders. Just to be safe. All showed between 135-145 psi, most at 140. Turning over sounded healthy too.

I'm starting to wonder if the intake manifold is warped. I've seen that happen........ I'll tear it apart and test the clearances with some plastigauges.

 

[gsxr]

White smoke can be caused by other fluids entering the intake. If there's enough fluid transfer to cause that much smoke, a cooing system pressure test should show a pressure/fluid loss (and, you'd find liquid entering a combustion chamber). The affected cylinder(s) may have the spark plug look different than the rest of the plugs.

A cooling system pressure tester is not expensive, and is a VERY useful tool to have in your arsenal. I think some FLAPS / McParts will offer a "free" rental where you buy the tool and use it, then return for a full refund.

 

[Raphial]

White smoke can be caused by other fluids entering the intake. If there's enough fluid transfer to cause that much smoke, a cooing system pressure test should show a pressure/fluid loss (and, you'd find liquid entering a combustion chamber). The affected cylinder(s) may have the spark plug look different than the rest of the plugs.

A cooling system pressure tester is not expensive, and is a VERY useful tool to have in your arsenal. I think some FLAPS / McParts will offer a "free" rental where you buy the tool and use it, then return for a full refund.

Do any of the intake-to-head bolts need thread sealant?

All plugs look relatively the same, no noticable differences. I pulled all the plugs and also spun the engine for a few seconds with the plugs out to spit out any residual fluid left in any of the chambers, but didn't notice anything spray out.

 

[gsxr]

I don't recall any intake bolts requiring sealant, but double-check the FSM to verify... would seem strange for any to enter a threaded hole open to either oil or coolant.

 

[Raphial]

I don't recall any intake bolts requiring sealant, but double-check the FSM to verify... would seem strange for any to enter a threaded hole open to either oil or coolant.

I didn't think so, and I didn't see anything in the manuals... just thought I'd ask. If a bolt does need sealant, and the gasket surrounding the bolt hole isn't water-proof/ready it can seep through. Usually in cast iron blocks.

So an update.

I filled it up with coolant again, then unplugged all of the vac connections on the intake to rule out any possible vac leaks, to set a controlled start-up. It started right up and idled about 1100 rpm until it warmed up. Ran for about 15 minutes.

No sign of overheating, and monitored the tstat and exhaust ports on the exhaust manifold with my thermometer laser. Seems to be no misfires, all cylinders run at equal temps. Tstat opened about 8-9 minutes in at ~180* and held.

Car didn't smoke much at all for the first 3-4 minutes. Then it did it's usual thing, smoked up the whole shop. I still let it run directing the smoke outside. It was up to temp for 5+ minutes idling. The idle dipped once, then after blipping the throttle it even'd out and idled smoothly.

A lot of coolant went down the first two cylinders of the front of the block, and I suspect that it saturated the catalytic converters and covered the inside of the exhaust. The car was jacked up from the front, and would trickle the water down the pipe if it made it that far.

I'm starting to wonder if I'm burning all that coolant/glycol out of the exhaust. I ruled out the EGR, has a brand new fuel pressure regulator, searched for vac leaks and found none, all the signs indicate such.

I'm gonna burn some cataclean through the system and just drive it. Other than the smoke it seems to run normal.

Lastly, the coolant res is normal this time. I guess it wasn't full before... even after three times filling it. Now it stays at the max mark. Doesn't seem to losing coolant.

 

[Raphial]

Another update.

I smoked out the valves/cats trickling Seafoam through one of the larger vac lines. Burned out a lot, and seemed to help a little bit with the valve clatter and idle. Though it wasn't a big problem before.

I ran it pretty hard too, went around the block. Still burning out water, and it's definitely water. Comes out the tail pipe like vapor.

I checked the coolant again, still no change. No loss in fluid. After running it hard the temp went to ~100*C before I cut it off. I ran it for about 20 minutes.

Other than the cats or smog/air lines being saturated or something I can't think of what else it is. It's still burning out a lot.

 

[Raphial]

Third update.

I did more inspection, triple checked everything I could think of. Eventually my gut told me it's just saturated catalytic converters (it smells like it too). So I just hopped in and drove it.

To my surprise it ran really well. Best it's ran since I've had it, and I'm not even done with the maintenance (I was stuck on this). Didn't overheat, coolant is still consistent at the same level, no coolant loss, and the smoke mostly went away. About 90-95% of the smoke/vapor stopped but still smokes a small bit when idling in park. But leaps and bounds better.

The only issue I have now is when in Park or Neutral, the idle surges up and down a little. Not a misfire but the throttle control seems to be trying to compensate for an unknown problem. When in gear, it idles low and normal with no idle fluctuation, and idles really smooth. Can't even feel it.

So not sure what that's about. Service Engine light came on, self-test showed only code 6 under the basic DTS diag without a tester using the on-board light.

Other than that, drives great. This has been a learning lesson.

 

[gsxr]

Good to hear you aren't consuming coolant! That's crazy how much liquid got into the exhaust system.

Does your E420 have ASR, or no ASR? There will be an "ASR" warning light near the ABS and Check Engine lights on the dash, along with a snow chain switch on the console, etc.

The engine should only idle at 1000rpm for a few seconds after a cold start, then start dropping in RPM. At operating temp it should be 650rpm in P/N or 550rpm in gear. Check Engine fault code #6 is "Idle speed control inoperative". You'll need to get a hand-held blink code reader to check for fault codes on the throttle control / idle control module (E-GAS if you have ASR, T/LLR if you do not have ASR). See the "De-Coding" subforum for more info on pulling blink codes.

 

[Raphial]

Good to hear you aren't consuming coolant! That's crazy how much liquid got into the exhaust system.

Does your E420 have ASR, or no ASR? There will be an "ASR" warning light near the ABS and Check Engine lights on the dash, along with a snow chain switch on the console, etc.

The engine should only idle at 1000rpm for a few seconds after a cold start, then start dropping in RPM. At operating temp it should be 650rpm in P/N or 550rpm in gear. Check Engine fault code #6 is "Idle speed control inoperative". You'll need to get a hand-held blink code reader to check for fault codes on the throttle control / idle control module (E-GAS if you have ASR, T/LLR if you do not have ASR). See the "De-Coding" subforum for more info on pulling blink codes.

Can you inform me what the names are of the two relays underneath the ABS module plastic cover at the front of the driver fender area? Thanks!

 

[nocfn]

Flux Capacitor

(local smart ass)

 

[Raphial]

Flux Capacitor

(local smart ass)

So you're telling me I got TWO flux caps????? Double the power

 

[nocfn]

shwing! You can stay...

 

[Raphial]

I still need the two names of these relays if possible! I keep seeing diagrams list them as k1, k2 for ASR/ABS diagrams.