jdmsuper7

iTrader: (1)

This saga is now entering its 4th week. Here is the basic backstory:

3 weeks ago: Drove car about 150 miles in 2 days, everything was fine. Start car up the next afternoon, start driving it, and it slowly overheats. Kill car at 210F. No pressure in radiator, and litte coolant in upper rad hose.

Replaced tstat, no dice. Tstat has been checked and works in water on stove.
Replaced water pump, still nothing.
System has been backflushed (garden hose kit), and has been bled any way I can think of. I'm pretty confident that there is no air in it. Still nothing. I can't get the tstat to open at all.
No leaks that I can find. Its never lost coolant. System was still full when it initally overheated.
I can't find any visible damage on the pump housing, or in the inlet/outlet from the front iron.

Other random bits that I've found while testing this stuff:
Coolant will flow with great vigor out of the BAC return if it is unplugged.
Lower rad hose will get hot on the top 1/2, but remains cold near the bottom, rad never ever gets hot.
Even without tstat, water will not flow up the tstat neck, but does leak alot since there is no seal and I haven't cored a tstat (should I?).

PLEASE HALP!!!1111
I'm at such a total loss at this point. I'm sick of auto-x'ing other peoples' cars. I just want to drive my baby again.

VacavilleFC

water pump is damaged? i have no idea just thought i'd throw out an idea

steve2323

well when i had an overheating problem i did the same stuff just to find out it was air locked in my colling system. i just losened the bleed screw, filled her up and never had a problem after. the bleed screw is located at the top left side of your rad, its just a little plastic screw. losen it and fill your rad untill fluid comes out around the screw. ( u will need the screw almost all the way out)

Sideways7

iTrader: (7)

That is a dead giveaway of a clogged radiator, since you have determined that the t-stat is good.
http://aaroncake.net/RX-7/cooling.htm

jdmsuper7

iTrader: (1)

Yeah, I think I am gonna completely drain everything and refill it. I was thinking about it as I was driving home and I think that will be the next course of action.

Radiator is new koyo, I highly doubt it is clogged.

Thanks for the input so far. I really need to get to the bottom of this, its starting to drive me insane.

86gxl_fc

could it be that somewhere in the block.. it might be clogged?
since your saying that it starts heating up the the rad doesnt.
maybe it cuts off somwhere.

FrankV702

iTrader: (14)

Do you have an aftermarket temp gauge thats tellin you its at 210 degrees? What about the water pump? have you checked that yet?

twistedriver

is fan clutch any good? Warm up to normal temp, stop engine and see if you can spin the fan with your hand. If you can the chances are the fan clutch is dead.

jdmsuper7

iTrader: (1)

Aftermarket gauge in stock location. WP core is new, housing is used.

RETed

Water pump belt slipping?

Are you running no air pump with just one belt now?


-Ted

jdmsuper7

iTrader: (1)

Belts aren't slipping, or if they are they are doing so very quietly. No dual alt pulley, but I have a yoohoo belt on there instead.

edit: one at the guys at work, after pouring over the fsm with me, suggested that I add a "jiggle pin" hole (I'm thinking of using the smallest drill bit I can find to do it) to my tstat (mazda oem, yet it looks alot different than the one I pulled out, and notably does not have the "jiggle pin" that is referenced in the fsm). I'm thinking this is a pretty good idea. I'll post an update, feel free to add your thoughts before then.

rx7-kid

iTrader: (1)

You could try testing your fan clutch like what twistedriver said.. if you said you change all that stuff then its probably the fan clutch....i had to change mine. because my car almost overheat...i got a new rebulit engine now so im going to monitor mine very closely

SailingDr

I have a new radiator, thermostat, 4 year old waterpump that isn't leaking, rebuilte engine with 8000 miles on, new sending unit...but when I run the A/C and down the road at 3000 RPMs the gauge goes to 7/8ths full.... a laser temp gun showed the engine to be 218 at the sensor portion of the block. .. so
a. if she running hot.... ? > ? change the water pump??
b. if she is ok at 218..? then change the gauge?
? any suggestions?

RETed

When you changed the water pump, did you happen to inspect the machined surface on the inside of the water pump housing?
I've seen one water pump housing that was so pitted / corroded, that it made the water pump useless cause there was too much clearance between the water pump impellers and the water pump housing.


-Ted

fusion-turbo

Sounds like a bad water pump to me. Or slipping belts...

Maybe your water pump pulley is turning but the actual pump inside is not? Its an idea... i would pull the pump again and do a full investigation...

Sideways7

iTrader: (7)

Why don't you just run without the t-stat at all. I know its not good for regular use, but you could do it once to verify whether the t-stat is causing the problem. If it still overheats you can definately tell that the t-stat is not the problem.

jdmsuper7

iTrader: (1)

The housing seems to be in great shape. The clearance was something I was wondering about, but the surface opposite the impeller looks great.

Impeller turns, its a new unit (I thought it was a bad pump too lol, so I bought a new one).

If the above mentioned jiggle pin thing doesn't work, I probably will core a tstat and try. I triend it without a tstat and it ended up leaking A LOT out the bottom of the neck, so I didn't gt an accurate assessment.

Rx7Ridah

iTrader: (8)

i agree with the possiblity of either a bad clutch fan and/or clog somewhere. I have found clogs in multiple spots during teardowns. check your overflow hoses and make sure that they are clear. alot of time the water chambers in the housings fill with debris. also check that the pressure cap(s) are good. i would also pull the radiator out and flush it, also try pulling the drain plug from the block and flushing the block out. (the drain is located inside the drivers motor mount bracket it looks different then the other 3 i think its the upper left bolt.)

jdmsuper7

iTrader: (1)

Bump for new info.

I pulled pump and looked at everything. It all looks fine, no corrosion, and no obvious damage.

So I tried drilling a vent hole in the tstat. It seems like I get SOME flow now. Generally by the time the temp climbs to 200 or so the top of the radiator is slightly warm to the touch (as opposed to dead cold like it was) esp on the side where the inlet is.

I still have ZERO pressure. I've managed to get water in all of the hoses now. I took it for a very quick drive to see if a little load would help, but it didn't. Even after than, when I open the radiator cap I don't even get a "psshht", it just comes right off. I took the coolant line to the BAC off and ran the car, and it pisses water out of that line, so it seems like there is some pressure in the block. I'm really confused as to where all this pressure is ending up. The car is HOT, its a closed system, there should be pressure right? I'm really getting close to starting a part out thread...

Also, mods if you read this, can you edit the title to mention the lack of pressure?

apexFD

Thats what i was going to say...

but maybe AFR? Running lean? higher EGT?

Something definatly sounds clogged or not working.

-Ben

NZConvertible

Replace the pressure relief cap, the one with the hose going back to the reservioir.

lnlycrpr

you state that the radiator doesnt get hot. i'm thinking your radiator is clogged somehow. especially if the rad cap comes right off w/o a pshhht or pooring out the top, when your motor is hot. that doesnt sound right. at this point i'd check the flow through the radiator.

cptpain

iTrader: (1)

the fact that the BAC coolant line pisses coolant is not very indicative that you have pressure in your system, it just means the coolant is moving.


this might be stupid to you but can be overlooked sometimes:
get a new rad/tstat housing cap thats rated at 13psi.

the pressure relief cap is not another pressurized raditator cap, its just flat with o-ring in it.

put more coolant/distilled water in it, most times when ppl change thier water pump or anything coolant related they overlook putting more water/coolant in

jdmsuper7

iTrader: (1)

Is this different from a normal rad cap? I replaced the cap (on top of radiator neck) and didn't see any change.

cptpain - I filled it up thru the water pump before I put the thermostat in, and then filled the radiator the rest of the way (it didn't need much). Also, its and S5 and doesn't have the cap on top of the tstat housing.

Could this be a coolant seal issue? Obviously I'm not just gonna tear the engine down for the fun of it but might it be something I need to consider?

I really need to get a leakdown test done methinks. I hate to have the car towed to a garage just for that though. I dunno. I'm really at a loss. Its been 4 weeks now.

cptpain

iTrader: (1)

yeah it seems to me that after you've been replacing and checking every conceivable part of the cooling system, i would think its a blown coolant seal or a crack in one of your housings