tintagel

The short: Engine boils over, kinda looks like main coolant seals, but not all symptoms are consistent.

The long: '87 Base Model (4 lug). It was boiling over when I bought it, but the water pump was obviously shot and sucking air so I wasn't too concerned. Got that fixed and the mechanic told me that he ran it for several hours, idled it with the AC on etc (this is phoenix, so that's pretty torturous), ran it up and down the freeway and it seemed to be ok. Drove it home no problem. Started it up the next morning and the low coolant buzzer sounded. Being a bit of a newbie I stopped the engine and popped the rad cap (near the thermostat, none on the rad itself) and topped it up with less than a cup of water. Caped it. Buzzer still sounded, figured it was lying (old electronics right... ) and drove 20 miles w/ AC. Buzzer went off and on a couple of times in the first mile then it went quiet.

Sat idling in a parking lot with the AC on for something like 10 min and noticed that the car was developing a coolant pool underneath it. Temp got up to 2/3 to 3/4 on the guage before I shut it down. Spent the rest of the day topping it off every time I stopped and driving with one eye glued to the temp guage. Got home.

Next morning it wouldn't start. It would turn over just fine and even try to catch. After 3 or 4 goes with the starter it was obvious that I had flooded it (smell of gas) so I took my non-project car to work and let the 7 sit until I had time. I tried the 'disconnect the fuel pump relay trick' unsuccessfully. Got a buddy who is smarter about 7s than me to help out and he changed the fuel filter and fuel pump and then successfully pulled off the fuel pump relay trick. Pumped out a huge cloud of black smoke (expected). Pumped out a huge cloud of blue/white smoke (also expected). Pumped out a huge cloud of pearly white smoke (unexpected?). After 20 minutes or so the engine started to boil over again.

By this time I had spent much more time reading this and many other forums (fora? fori? - latin...bah!) - yay Google!

So here are the current symptoms:

• Cold start - no problem.
• Warm start - 2nd time I crank it.
• No visible smoke on start-up or idle.
• No signs of exhaust in overflow tank (oil, smell, etc)
• If I follow the enhanced top-off/bleed procedure in the FSM then I can run it around with no sign of a problem for several stops (3 miles to friend's house, 3 miles to Home depot, back to friend's house, home - stopping the engine every time and watching the overflow tank). Next day, low coolant buzzer, top it off again (maybe a pint to a quart)
• Local Firestone says the cooling system holds pressure (doesn't leak down).
• Local Firestone says the cooling system pressurizes to 30+ psi when they run the engine.

So far I've had 2 or 3 car savvy paople give me an initial diagnosis of a blockage in the cooling system (including Firestone - oh yeah, one of the service writers drives a 2nd gen 7, so they're not totally rotary ignorant). Then as they check it out I start to hear things like "I'd say its a head gasket, if it had heads..."

So, I'm afraid I'm looking for a JDM/J-Spec (or trying the Block Weld patch), but the symptoms don't quite add up. There's this little optimist in me who keeps hoping it is like the guy who had boil over problems and found a pinched relief hose....

So, I am appealing to your collective intelligence, what do you think? (Other than: "Damn! He sure is wordy!" )

theonlygreat

30psi while the engine is running is too muich. sounds like a blown motor to me. the rad cap is only supposed to hold 11-15psi according to the FSM.

tintagel

Yeah, the high pressure in the cooling system is the main reason I am concerned about it being a blown motor.

Is it possible that the water pump could create that much pressure with a sever blockage in the system? It just seems weird to me that the cooling system holds pressure (wouldn't it leak down if the seal was bad?) and I don't get white smoke out the tailpipe.

Aaron Cake

iTrader: (1)

Pressure test the cooling system. Keep it pressurized for 8 hours or so. You will probably find that it is leaking into the engine...

Also, see http://www.aaroncake.net/rx-7/cooling.htm

tintagel

Thanks Aaron.

Your page is very good.

Hopefully I get to test it tomorrow afternoon!

tintagel

Ok, I'm going to really show my newbie colors here:

I just pulled the thermostat and it says 195F on the inside of the copper bit. The FSM says that it ought to start opening from 177F to 182F, and be fully open by 203F. So, I know this is dumb, but is the stamp on the thermostat the full open temp or the beginning open temp?