When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hi everyone,
I'm very new to rx7's, as in this is my first one I've owned haha. It's a 1986 RX7 (Canadian luxury model??), everything stock that I can tell. It has 136k miles. This is also my first post- kind of a last resort reach for help. When I bought the car, it had a coolant issue where the reservoir would become pressurized then start volcano-ing out of the top breather hole. I replaced the thermostat, water pump, and a OEM radiator cap. Also, multiple flushes with new coolant and pressure flushing the system with a T-fitting in the heater core hose with a garden hose attachment. I found out later that the problem was the small rubber tube inside the reservoir for the overflow.
It swelled, so every time the car warmed up, it pushed coolant into the reservoir. When it cooled, it just sucked in air like a straw with a hole in the top. Eventually volcano-ing out the reservoir.
I fixed that issue. Now coolant is contained in the system, the reservoir rises and goes down like its supposed to. I have a new problem though. Whether I use a Lisle coolant funnel or keep the radiator cap on, there's small bubbles that come out the funnel or the reservoir. I know that usually this means the coolant seals are blown and a rebuild is necessary. Thus, I used the blue liquid combustion leak detector. I put it on the radiator, did not detect a leak. I created a set up so that all the bubbles that go into the reservoir have to go through the leak detector (picture below, acts kind of like a bubbler?), still did not detect a combustion leak. Now I'm stuck between is this normal, or maybe my leak detector was bad? I removed all the belts from the water pump, and bubbles still came out. I know it's not cavitation of the water pump. When I rev the engine, the bubbles stop. No large bubbles come after, just the same small constant bubbles. Also to add, there's no white smoke on start up or revving, and the exhaust smells normally- not sweet.
I'm really stuck on this one guys, and I don't want to pull the trigger on a rebuild kit unless it's the last option. To me, all the signs are pointing to a rebuild, is there a way to for sure eliminate other options? Am I missing anything? Is this normal? Any help from experienced RX7 guys would be so greatful. I'd appreciate any advice in general too haha.
You could pressurize the cooling system with a cooling system pressure tester and see if it holds pressure. You could also use an Air Lift and put vacuum to the cooling system and see if it holds pressure as well.
Are you having any issues at start up? Have you pulled the plugs to check them for signs of coolant in the combustion chamber? More than likely though, if you had a coolant seal failure and it was pressurizing the system slightly, it would be closer to the exhaust portion of the coolant seal as you know. It could be that there is just air in the system that needs bled out.
I would personally just make sure the system is bled, and drive the car for a few days and keep a close eye on the coolant level.
Keep your overflow res full and keep an eye on it. Early FC has a bleeder on the rad. The system should self bleed. If you need bleeding your res will let you know. It should eventually stop demanding more coolant. It's normal to add 3-5 times after coolant flush. If you notice in, let's say a week, that your res is still running low then you have an issue.
I have pressure tested it before working on it, when I first bought it. It held a steady 13psi like the radiator cap does. I want to pressure test it again though. I have put the car through many heat cycles and drove it around a small lot (doesn't have insurance right now so I can't legally drive it on the street yet). Even after running for so long, the bubbles are still present.
I haven't pulled the plugs out yet, what should I be looking for if they're contaminated with coolant? White dry film?
Also, when I first bought the car, it had no troubles starting. It started right up, revved to 3k for it's warm up, then dropped back down to idle. Since then, when I was doing the cooling system work, I also rebuilt the OMP lines and cleaned the oil injectors. After I did that work, it still starts fine, but it won't do it's 3k rev warm up. I'm not sure why it isn't anymore, I haven't dug quite into that yet. Any suggestions would be helpful haha. But even now when it starts, revs, or drives, there's no white smoke or anything.
I will try to get insurance on the car soon and I have the ability to use an Air Lift at a shop, so I may use that then drive the car for a while and keep an eye on it. Thanks for your guys's inputs so far!
If there's wet coolant on the plugs, you'll be able to see the coolant of course. If its being burned, the plugs will look somewhat clean or it can have a buildup of white crust on the porcelain. It may be that the leak is super small and not very noticeable yet. This is an odd issue because usually when you have a bad coolant seal, you'll get coolant consumption, overheating, or alkaseltzer like bubbles jamming their way through the radiator. Keep us updated on what you come up with.
Are you overheating? Are you losing coolant? It's too bad it isn't insured. Have you put your nose up to those bubbles? Do they smell like exhaust? Any oil film in your coolant? Discolouration? You may have an air pocket at the water thermosensor -that could be why you aren't revving to 3k. If air is surrounding the sensor then it could be fooling the ECU with a bad reading. Then again, I'm not sure if this will affect the AWS. I don't have the AWS.
EDIT: A heat cycle will not rid your bubbles like driving around, hitting bumps, going up and down hills, cornering, braking and accelerating will. If you aren't overheating, not losing coolant or experiencing weird cold starts with smoke then it could be simply a matter of actually driving the car and topping up the res a few times.
Last edited by Rotary Alkymist; 04-23-18 at 11:24 AM.
No I'm not overheating, the temp gauge sits at about 1/3 on the cooler side. The bubbles don't really smell like anything, and there's no oil film in the reservoir.
Update: I put the exhaust back on last night (was open header for a while because I replaced the drive shaft). I was warming the car up after I was done, and I revved it to about 4k and could hear "waterfalls" behind my dash, assuming more air pockets in my heater core. I had this problem when I first bought the car. More constant bubbles out of the reservoir, hopefully just these air bubbles bleeding out. I will try to incline the front right of the car and bleed out more air today. Next step will be to work on insurance so I can actually drive it around.
Another problem did occur last night also (of course, fix one- break one). After I revved up to 4k, it went back down to idle. I revved it up to the buzzer red line and dropped it back down to idle. Well the buzzer kind of half quietly stayed on. No dash lights (low coolant). After that, each time I revved it, the engine would increase normally, but the tach would top off at 2k and the buzzer would freak out. Also, I noticed that my temp gauge never increased, and the car was at operating temp so it should have moved a little.
Not sure if I have an air pocket and bad grounds or something but I'll look at it today, see if I can find anything out. Will keep you guys updated. Hopefully it's just an air pocket and not time for a rebuild yet
04-17-18, 11:26 PM
