4agze build questions

[ae86boy]

Well...it continues to overheat. It started off well, but by the same time as usual it was running too hot and clocked in similar temps as before (~110c block temp as measured on outside with IR thermometer).

Coolant is visibly flowing through the rad...I can watch it when I pop the cap off. I do note that the cap is not noticeably holding pressure...that is to say that the cap when released doesn't "psssht!", which is something it always did until this year. Other than that, I see no alternative other than either running some kind of toxic rad-flush chemical which may or may not eat the radiator/head or tearing the entire engine down to the block and hoping that I find the plug along the way. This is something I really do not want to do, as I have a second project car I would rather invest the time in and I am at the end of my wits, so to speak.

I do have a "lambda" sensor (wide band) mounted in the car...it never runs leaner than about 13:1 in regular cruising and under throttle will go as low as 10:1...so its actually quite rich.

Thanks again to everyone for their help.

[Cuzzo]

Have you tried a new cap first?

[trdee]

I dialed the timing right off the motor, basically grabbed the dizzy and turned it as far retarded as possible...and it still overheated exactly as before...same amount of time, same road etc, but with an outside temp about 15c lower

4AG manual says timing too retarded can cause overheating.......

[JoJo]

Got those pics of your water routing?
Have you double checked this?
J

[Sam_Q]

what about a crack in the block between a chamber and a coolant passage? it's highly unlikely but it would cause all the things you mention: heater core cracking a leak, radiator cap giving up, high temps, etc...

either that or the straightness of the block like what was suggested earlier.

[ae86boy]

http://i38.photobucket.com/albums/e1...y/untitled.jpg

Sorry for the delay...i've been really busy.

here's a really, really crappy picture that gives you the general idea as to the routing. Yes, I've tried new caps...I have a TRD 1.3 bar, a Delphi 1.3 bar and an OEM 1.0 bar...none of them seem to affect the cooling temp in any way.

[JoJo]

Have you ever havd good operating temp with this setup?

Because from what I can see, It's looks kinda wrong dude......
Where have you got the thermostat located?


- 4AGE water flow diagram - http://www.billzilla.org/4agwater.gif

[YLD-16L]

Have you ever havd good operating temp with this setup?

Because from what I can see, It's looks kinda wrong dude......
Where have you got the thermostat located?


- 4AGE water flow diagram - http://www.billzilla.org/4agwater.gif

His pic is exactly the same layout for coolant flow as the pic you posted from Bills site, only difference is old mate hasn't got the heater lines or throttle body lines. Neither of which should affect the cooling ability of the engine.

He has the RWD water pump with the thermostat sitting on the back of it.

The setup looks fine in terms of layout and flow path.


Everyones given you other ideas for what the problems could be but it sounds like a blockage of some sort that you haven't fixed/removed. How's the water pump, still got fins on the impeller?

[ae86boy]

I haven't actually taken it down that far and looked at the pump itself, but I assume its okay? Its clearly flowing.

I have:
changed the coolant twice
flushed the rad and block forwards and backwards
changed the rad caps
advanced and retarded timing
removed and added boost
added a thermostat...and removed it again just to see what happened
removed the heater core
changed the rear loop hoses to make sure they weren't kinked

The only thing I'm thinking is bad engine tolerances at this point. The whole "overheating" thing started when I machined the cylinder head for flatness. Now, it could be cracked or it could just have a tiny gap in it...but that seems to be the thing that was changed most recently...which is usually the cause if its a new problem, right?

Yes, the car used to run stone-cold set up this way, even under 15psi in the summer. It started blowing head gaskets and then once it stopped that it started this overheating nonsense. I did drive it for several thousand kilometers without incident before all of this started happening.

[nick.parker]

This e-mail may not be helpful but anyway.....I am good at demonstrating the way not to do things sometimes!!!!

I just figured out why my car has kept 'just' overheating over the last few months. I have an electric coolant pump, and a couple of months ago, around the time I first noticed the overheating, I had changed the way the pump is controlled :- Basically I had slowed it down about 15% around normal thermostat temperature. NOW, I presume the pumping characteristic of impeller style pump must be exponential with speed - because slowing pump a little must have greatly reduced the flow.

My car has been mostly sitting for two months of sitting while I mulled over my misfortune at thinking my headgasket must be stuffed.

Anyway , today I increased the pump speed after someelse sparked a random thought in my head, (the pump is driven by some custom electronics as a function of coolant temperature) back to where it use to be and voila :- No boiling, no high temperature. Idles indefinitely, doesn't overheat when boosting up a long hill.....all fixed!!

Anyway now I have spare ARP head studs and a spare TRD gasket. Definitely pays to eliminate everything BUT the head gasket first eh!

I also learned that some bubble are acceptable coming from an open coolant nozzle when the car is up to temp, and it not a result of leaky head gasket....apparently its usually frothy if thats the case - (I've got no experience with failed head gaskets)

Nick.

[TERRA Operative]

Yep. Impeller pump have an efficiency curve. Come off the curve, and you loose substantial amounts of flow.

[35rolla]

hi im not sure what ignition system you run ie dizzy or cas. check your timing if its adjustable. to much advanced or retarded timing can cause all sorts of problems. seems like you have checked everything else. my 4age when i got it was retarded 30deg idled ok but cooked on the road regardless of outside air temp.

[ae86boy]

Well, its been a year since I touched the car...I became so frustrated with it that I stopped working on it and focussed on my other ae86 project instead. Now that the new one is off for paint I finally have time to look at the old one again.

On a hunch I pulled the head off...I figured that if it really came down to it the only way to know for sure was to rebuild the entire engine. I disassembled everything to find that some of the head studs I had put in to prevent any kind of headgasket questions arising were actually loose! I had followed the manufacturer's directions exactly, but somehow they had come loose over time. Some were still tight...this leads me to believe the block may be warped?

I am going to take the head in today to get it checked along with the gasket. Surprising that even with the studs in loose the head still held under all that boost. Could be that they loosened over the winter while parked as well. I did note that well the headgasket seems to have sealed well, there was "cooked" coolant in the passages of the gasket...like a film across the hole? This was on the exhaust side of the head only.

Just thought I'd post up something to re-start this old thread...I hope I'm allowed to do that? Keep you all posted.

mac

[AE25]

are you saying the nuts had come loose? or the stud had unwound from the block?
Dried coolant could be the result of having it parked up for so long? if the coolant level had sat at head gasket height and some form of surface layer has created a hard crust on top of the coolant? I can't imagine you'd caramelise the coolant from over heating it. there must've been absolutely no flow for that to occur. (if it does occur at all).

[ae86boy]

From what I could see, the studs had come loose...though it could have been a combination of some studs and some nuts.

Yes, I could see how the coolant sitting so long would cause it to have that film...but should the head not have coolant pressure and fluid all the way to the top assuming proper bleeding of the system? Would being full of coolant not prevent this film from occuring?

Thanks for the reply!