Burning Coolant (BHG? Intake?)

[Jkm3141]

Hey I posted this over on celicasupra.com since i have a 7m-ge in my MK2 and reciveved good information, however im curious about a few things that people who have more 7m-ge knowledge would be able to help me with. This was my posting over at cs.com

When i got the 7M-GE installed in my car I knew it had a small coolant leak (possibly broken head gasket). Part of the reason I got the engine for 400 (150 more for tranny). Recently the car has gotten much worse. When i was cruising through town with a buddy of mine with a stock Infiniti G20t (slow as shit.) i noticed the car was idling rough (about 500RPM and sounded like a harley (kinda like a misfire). I told myself I would figure out what was wrong with it when I got home. Didn't need that long as 3/4 of the way home at a light i noticed a slight cloud of white smoke that was burning coolant (i will NEVER forget the smell of burning coolant. After having the 23 year old radiator that came with my car explode and spray coolant all on my old 5M... ugh). Upon smelling this I'm like damn, there goes the head gasket (knew it was coming). About a block away from my home at a light it wasn't smoking as much but when i accelerated from the light (calmly, duh) The engine bogged down heavily, as if the coolant had built up while idling at the light (that seems incredibly fast for a head gasket, considering the engine was on). However tonight me and a buddy started pulling stuff off the engine. we got everything off plug wise (on the head, not the main engine grounds to the block because we aren't gonna pull the engine). We also pulled the distributer (I got a question on how to re configure the timing of the distributer, because now its going to be out of alignment and as far as I know, there weren't any marks on the distributer to align it...?) We took off the intake manifold (since the 7M-GE manifold is three sections we disconnected the manifold at closest to the block without fully disconnecting the manifold (hard to describe). Upon inspection of the manifold (both disconnected and the last part remaining attached to the block) we saw a lot of coolant built up. The original owner of this engine (The guy who had it in his Cressida before my friend put it in his MK3 (he got the MK3 without an engine for real cheap and got this 7M-GE cheap)) had i believe taken the whole intake off and cleaned and polished the manifold (based on the age of the gaskets holding the sections of the intake together, and the cleanliness of the intake). If that owner possibly messed up the assembly of the intake, could it slowly leak Coolant into the intake (and subsequently the engine), and just progressively got worse until the other day that I mentioned earlier? I am going to do a compression test on the engine (gotta borrow the compression tester from my friend tomorrow hopefully (hard to get a hold of, but its ok cause he has a beastly STi)) and that would prove if it was a BHG or intake problem. If the engine backfired some during the heavy bogging down I mentioned it could have pushed coolant into the intake? the coolant wasn't just in the lower pipes but sprayed all through the upper intake. I know this is like a 99% chance its a BHG but i still want to ask. Thanks for the long read, I just wanted to mention all details.

What are the chances of it being an Intake problem? If it is a head gasket, do you all reccommend changing the head bolts (85K miles), as well as machining the head (if it doesnt look to bad once the head is off). I'm going to do a compression test this evening when I get off of work, and will post the results of that here. Thanks.

 

[cuel]

Hmmm... have to take a throttle body off to see how the coolant passages are routed, and whether or not a torn/faulty gasket could possibly leak coolant. Maybe if it(t.b.) was cracked in just the right place...
As far as anything technical on the 7m, you need this: http://cygnusx1.net/Supra/Library/TSRM/MK3/ It's the Toyota Supra Repair Manual. Bookmark it, and consult it for timing the dist., timing belt, and so forth.

 

[AJ'S 88NA]

I think there is only two ways coolant could get in the intake were you described it, one is what cuel described with the coolant line that runs to the TB, and the other is BHG. Well maybe one other way, somebody poured some down your TB.

 

[Jkm3141]

Well.... I finally finished the compression test (replaced starter that died). All cyl check out great. They were at 155PSI +-3 Psi. They did not leak out any pressure (i let each sit for over 45 seconds). Based on this I am really starting to think my headgasket is alright. What else would be causing the symptoms of a bhg that involves coolant? Or what else would cause coolant in the intake like that? I am thrilled by the results of this compression test because doing a head gasket is really not possible at this time in my life (college is expensive).

 

[thedave925]

there is one coolant line that passes threw the lower intake manifold and into the head:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?Section=CO&P=2
Look to the center of the picture and notice the line that heads "From Head" and follows up to the ISC and TB.
If that gasket seeps you could burn coolant.
As for the inside of the Intake Plenum, maybe the ISC bolts are loose.

 

[Jkm3141]

there is one coolant line that passes threw the lower intake manifold and into the head:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?Section=CO&P=2
Look to the center of the picture and notice the line that heads "From Head" and follows up to the ISC and TB.
If that gasket seeps you could burn coolant.
As for the inside of the Intake Plenum, maybe the ISC bolts are loose.

so basically check or bypass the coolant lines going into the manifold? the guy i got the engine from said that the coolant lines running through the manifold that you mentioned were essentially useless unless it was winter (something about keeping the manifold the right temp so its not too cold to crank). Do you guys agree with this? would bypassing the entire intake coolant lines be a bad thing to do?

 

[AJ'S 88NA]

so basically check or bypass the coolant lines going into the manifold? the guy i got the engine from said that the coolant lines running through the manifold that you mentioned were essentially useless unless it was winter (something about keeping the manifold the right temp so its not too cold to crank). Do you guys agree with this? would bypassing the entire intake coolant lines be a bad thing to do?

Mines bypassed, helps keep the TB a little cooler in the summer. I don't drive a lot in the winter, your buddy is bascially right, I think is suppose to help with cold weather driveabilty. In your climate might not be a bad idea.

 

[Jkm3141]

I have almost no intention of driving this car after snow starts falling. First off, as you know, Supra's have a lovely traction problem in the rain, let alone snow (even more so in a MK2 not mk3 due to weight, but y'all know that lol). and Second off, I wanna keep Rochester's excessive use of salt away from my already bad shape body. As far as the problem's I am having.... Would you recommend that I start by re attaching the intake and distributer (started taking stuff necessary to work on a BHG before I did the compression test (I was waiting for my friend to let me borrow the compression tester, which I ended up purchasing anyway.)) and bypassing the coolant lines and see if the problem's fixed? I don't want to run the risk of the engine still running like it was before (heavy coolant burning...) I really am curious as to how to approach this problem. I am pretty sure the problem is in the intake coolant lines or plenum's(pipes?). I understand that the intake coolant lines are not that needed and if i bypassed them, the car would run alright. I have looked over the guides and diagrams for the intake and coolant systems an insane amount of time and am not quite sure how to approach this problem from the perspective of it not being a BHG. Thanks for your help guys, Celicasupra.com has been pretty helpless on this specific issue (they said its no doubt a head gasket (seems unlikely now) or do a compression test. No response since.). I know you guys know 7M's way more then they do and any kind of info would be very useful. Thanks:icon_razz

 

[shepfly]

Since you have the intake manifold off the head why not borrow or buy a radiator pressure tester and pressurize your cooling system to see if you can find the actual area where the leak is? Just don't take the pressure too high and damage some part of cooling system. System operating pressure is on rad. cap or in TSRM. If your creative you can make your own tester.

 

[AJ'S 88NA]

Have you cranked the motor any, by hand or starter? If you have you'll have to make sure you are at top dead center on #1 and the rotor is pointing at the #1 wire when you drop in the distributor. Check around the gasket that goes between the head and manifold. On that section of the manifold there is a small pipe mounted that the hose going to the ICS hooks to. That gasket has to seal around that hole that goes into the head. If they didn't change that gasket when that had the manifold off, then it could be leaking coolant there, like cuel stated. It has a little copper ring that compresses when you tightened the manifold.
If it was leaking around the TB connections and it has a hole/crack you'll have to plug those two holes or you'll be sucking air there. Did you notice any coolant in the Y pipe? If not it's probably that gasket leaking. Notice any coolant inside the ISC valve? I don't know if it could leak coolant into the manifold, maybe. You should be able to see were you were loosing coolant, on the block, the hoses to the TB or ISC, somewere if it let loose like you thought it was a BHG.

 

[Jkm3141]

I am in the process of doing all those things. All of which are helpful information. I have a quick question though. When I did the compression test the engine was not warmed up at all. It had been sitting for a few days (with the intake off and distributer, so i couldnt have the engine warm up for the compression test). Are the chances that its a BHG realistic based on the temp and other symptoms of the problem (speed of the leak while idling)?

 

[AJ'S 88NA]

I am in the process of doing all those things. All of which are helpful information. I have a quick question though. When I did the compression test the engine was not warmed up at all. It had been sitting for a few days (with the intake off and distributer, so i couldnt have the engine warm up for the compression test). Are the chances that its a BHG realistic based on the temp and other symptoms of the problem (speed of the leak while idling)?

I think you said you had like 155lbs on the compression test? Should be OK. Did you notice anything in the oil? If not the HG is probablly OK. Have you been able to see were the coolant was comming from?

 

[Jkm3141]

I think you said you had like 155lbs on the compression test? Should be OK. Did you notice anything in the oil? If not the HG is probablly OK. Have you been able to see were the coolant was comming from?

Nothing major in the oil that I could tell (it looked like new ish oil (less than 1000Miles on it so its still pretty clean). I assume the coolants coming from the intake. Once I get out of work tonight I plan on finishing the intake install and bypassing the manifold coolant lines. Then i will know If it was the coolant lines that were leaking. I doubt its the headgasket if the compression was 155PSI even not leaking for all cyl. I was burning serious amounts of coolant and based on the amount of coolant goo i found in the intake I bet it was that.

 

[Jkm3141]

Well I finally got all the stuff put back onto the engine and the distrbuiter timing set properly. The car was running seemingly fine. I took it for a quick drive around the block to let it heat up, and by the time i got back i noticed the same idle issue and burning coolant. Stopped the car, waited a few min while i found a socket, and started it. and got a nice blast of coolant smoke out the back. I know this is beating around the bush but Is there anything else that would cause this to happen then a BHG? Would the engine being cold cause the compression to be perfect but when the engines warm it has that big a leak? Thanks for all the help thus far

 

[AJ'S 88NA]

Well I finally got all the stuff put back onto the engine and the distrbuiter timing set properly. The car was running seemingly fine. I took it for a quick drive around the block to let it heat up, and by the time i got back i noticed the same idle issue and burning coolant. Stopped the car, waited a few min while i found a socket, and started it. and got a nice blast of coolant smoke out the back. I know this is beating around the bush but Is there anything else that would cause this to happen then a BHG? Would the engine being cold cause the compression to be perfect but when the engines warm it has that big a leak? Thanks for all the help thus far

My thinking is that if the motor is warm then the rings have expanded which would provide a better seal. There is only three places that coolant enters the intake. The TB, ISC valve, and the hose that goes from the ISC to the head. Have you had the ISC valve off to look at it? I don't know of anything else that would pour coolant into the head. The only other possibility would be a cracked head that would be in the area of the intake where it attaches to the head. It would have to be a pretty good size hole to spray up into the intake as you described. Maybe somebody else would have another idea?

 

[CRE]

As AJ said, warm engine make happy seal!

Also, coolant flows through the lower intake manifold's flange under cyl. 2 or 3. If it's not a BHG the wall of the TB or ISC eroded enough to permit coolant into the intake or the manifold gasket is leaking.

Your oil and coolant don't always contaminate eachother when the HG goes.

 

[Jkm3141]

As AJ said, warm engine make happy seal!

Also, coolant flows through the lower intake manifold's flange under cyl. 2 or 3. If it's not a BHG the wall of the TB or ISC eroded enough to permit coolant into the intake or the manifold gasket is leaking.

Your oil and coolant don't always contaminate eachother when the HG goes.

thanks for both of your ideas, when I get a chance I'll check those options. I know its most likely a head gasket but I really just want to make sure. Even more so since the compression is good on the engine when cold. I would do a warm compression test but considering how bad the burning of the coolant is I don't want to crank that engine more than i REALLY have to.

 

[ImperfectSupra]

subscribed, i have the same symtoms. losing coolant but not over heating. the car is still power ful and compression is at 140 all around, i cant see any physical cooant puddles but have to fill it up every three days. i do get a cloud of white smoke when cold starting. i will post in a few days afteri pull the tb and isc. CAn a small leak in the isc and tb cause over heating or the resvoir to overflow??? thanks.

 

[CRE]

Are you loosing coolant via the overflow? The most common causes of that would be the radiator cap or headgasket. In this case I'd start with either having the radiator cap pressure tested or simply replace it. If that doesn't do it move on to the following suggestions.

If you're loosing coolant and can't tell at all where it's going I'd start with adding UV de to the coolant, go for a short but spirited drive (once the engine's up to temp), then pull out the black light and look to see if it's leaking anywhere in the coolant bay.

If that doesn't pan out, pressure test the coolant system and look for the fountain.

Then move on to a pH test of the coolant to see if combustion gasses are getting in the coolant system.

 

[ImperfectSupra]

a mechanic have told me after a compression (very good compression) and leak test that the leak is some where between the head and firewall but i cant see any coolant or wet spots. he said that i could be a hose or plate. or crack block. ? any suggestion. its supposedly BEhind the coolant hose that come out of the head by the firewall. i HavE replaced the thermostat and cap with geuine toyota parts a few weeks ago. By the way the car doesnt overheat just lose a little coolant......Meanwhile im doing a complete flush with a liter of radiator cleaner. just have to drive for 3 more hours. thankd