I don't know what to do anymore, as search has failed me. Failed me.

I've recently dropped in a used engine into my RX7 (Purchased courtesy of Rotary-guy on here, he guarenteed there was not a coolant seal problem and said it only had 10k-15k on it), and have been trying to iron out the bugs in the coolant system like mad.

So far:
Testing the coolant system for hydrocarbons returns a negative
The coolant system holds pressure for the most part
I have been unable to fully purge the air from the cooling system. I get a continual stream of small, tiny bubbles when trying to bleed.

I'm not sure what could be causing this stream of tiny bubbles. I just spent about a half hour outside, trying to purge the air fully out of the coolant system, but that stream of tiny bubbles stays a constant.

I may have fixed the issue, however, it also would not suck coolant back in that was expelled into the overflow tank. Considering the engine, it can't be a coolant seal - I've replaced all the hoses on it but one, not really sure what else to do at this point. Could it be a pipe? The heater core? Something like that?

 

what is your bleeding method?

I used one of those funnels that bleed the system, it comes with adaptors that hook up to where the radiator cap is, seemed to do the trick.

 

Do the bubbles increase with rpm? how have you been bleeding the system?

 

Basically, I've got a funnel that matches up perfectly with the fill neck. Drop it in, put in a bit of coolant, let sit and add coolant as necessary.

I'll check if they increase with rpm, I need to get another foot so to speak to test that.

 

how long did you bleed it for also?

 

but does it have the radiator cap adaptor so that the funnel itself stays full of coolant?

 

Actually, no. What is the necessity of such a thing? I just top off the funnel by hand to ensure it has coolant in it.

30 mins-1 hourish. Quarter tank of gas's worth of bleeding.

 

otherwise it will not bleed, you cant just have the cap off and expect it to bleed.
You need the funnel to STAY full the whole time, the air will burp out through the funnel.

 

Huh.

I'll look into picking up a Lisle then - however, I'm not so sure why this would cause a continual stream of small bubbles.

 

by full I mean coolant in it at all times, not full to where its over flowing, but full enough so that air is never introduced into the system.
You need to let it run and get up to temp where the thermostat opens.

I never had a air issue until my tii swap, one of these is now in my took box

 

after your initial bleed and warm up do you turn the heat on and the fan all the way up? That has worked for me with out any fancy funnel mechanism. Just as coolant as necessary as you are doing. But, from what I've understood if you don't run the heat at full blast while the coolant is warm and you are bleeding air will get trapped in the heater core.

 

I have owned these cars for 20 years, I also never had a air issue until last year, once you have a air issue once you will understand.

dammed if I know why, but the funnel does the trick, its cheap too and makes filling your radiator very neat and clean

 

Heat's on full, but I never bothered to turn the fan on.

Would that cause it possibly? Huh, weird.

 

In my opinion I don't think you really need one of those tools although it certainly couldn't hurt. As per the FSM the coolant leaves the radiator via the lower radiator hose, so if there is air on the top of the radiator it really shouldn't get sucked back into the system.

 

Robb, I suppose I'm lucky I've never had an air bleed issue but, blaen99 I think it does make a difference if the fan is on, I'm not sure why but thats how I got my system to fully bleed.

 

How about this- I used to change my coolant every year, and never even had to break the bleeder screw.

Now I need the funnel, again im not asking questions, im just doing what works.

 

All right.

Just went outside after letting it cool off for 30-45 mins or so. Popped open the filler neck cap to start bleeding with fan.....

There was probably a pint or so of coolant missing. It's pulling air in from -somewhere- when it hits vacuum phase. Odds on the constant small bubbles being related to it pulling air from that somewhere?

 

Robb sorry wasn't trying to knock the funnel, just never had the need but I'm sure I will eventually. I'm not doubting your need for it what so ever, just trying to give my $.02. Blaen99 you might want to try the funnel method that Robb uses, he seems like hes got the same issue so it might be worth looking into before you decide on anything more drastic.

 

Make sure all your clamps are tight.I've seen guys Swear they have a coolant seal problem,and turn out to be a Hose clamp allowing air IN to the cooling system.But for unknown reason Not show any drips.

 

Considering the amount of air in the system after shutdown (The entire upper radiator hose was empty), and I made sure it was completely full before I shut it down...

I'm not sure about Rob's problem - checking his post history now - but I'll grant you it could be it. Does not make sense to me, however.

Urgh. This could be it. Did the clamps even create the steady stream of small bubbles?

 

I did not have a problem , rather the car would just run a bit warmer then I thought it should be running.

Obviously the OP needs to go over the basics, my advice is not a solution for a loose clamp or another basic issue, its merely meant as advice, I know I will never fill any anti freeze in any of my cars any other way again.

 

I had a hose clamp issue, where on my upper radiator hose right on the filler neck it was leaking out the bottom under pressure and it was in such a location that you couldn't really see it unless your head was where the fan is. So definitely go back and check your hose clamps. Also make sure that all the mating surfaces for the hoses to where they clamp are nice and smooth for a good solid connection.

 

you could have a leak so tiny that you cant see coolant dripping, again my advice is for that time when it seems like you just cant get all the air out of a healty system.

Mine was after spending alot of time and money on a engine build and swap, so I knew everything else was good.

 

I had small bubbles when I was running 10w 5 or whatever, it'd smoke blue and white alittle at times, after changing the oil blue smoke went away and now only white on start for 30sec, no more bubbles.

I didnt know you have to use a funnel thing or whatever, I just left the car on kept adding coolent till it was full and kept revving it till it was done burping out air.

 

For ****'s sake.

Brand new (worm) clamps, hoses, and radiator....

I just found the issue. I overtightened the clamps enough to cause a slight dent in the place where the hose connects to the radiator.

Yeahhh, brilliant.