Cooling system woes

[Fidhle007]

So my swap is running but I'm having odd issues with the cooling system. On the maiden voyage I blew a radiator which I attributed to the clutch fan hitting and breaking off most of the blades. I swapped in another radiator and wired up the stock aux fan to run on high as long as the key is on. I added a bottle of Water Wetter too.

This seemed ok for a bit, but then the heat stopped working and the temp started climbing again. I shut it down bled a bunch of air out of the radiator via the overflow hose thing, figuring I didn't have the system bled well enough and it just developed a big bubble somewhere. One thing I noticed as well, was that the coolant level in the tank had risen drastically and only went down again when I opened the cap AND had the small hose off the radiator. This situation has happened every time I drive the car longer than 30 minutes or if I push it at all. Same thing, heat stops, temp climbs tons of air in the system. Is there some fundamental thing that I have hooked up wrong or are my nightmares of a warp/cracked head justified?

Thanks,
Brendan

[1990m3]

it's just a bitch to bleed the system. Sometimes it takes me a while to bleed it out all the way. Which radiator are you using? It sounds like you have the 318is radiator. Fill the reservoir until coolant comes out of the bleeder screw a little bit. Cap the reservoir. Jack up the front of the car to make the radiator the highest point in the cooling system and then run the car. The gauge will get really high and then it will just start to erupt coolant from the overflow bleeder on top of the reservoir. It takes a while but works. Don't worry about your block/head yet. Until I got the system down I spent an entire saturday trying to bleed it out properly. Once you break the code for bleeding with that setup it's much quicker.

I did a search on bimmerforums in the e36 section about how to bleed the cooling system and I fond some helpful threads in there. If you're using a 325 radiator without the built in reservoir it should be very simple. Just run the car with the cap off the reservoir for a while and you'll be set. The initial coolant fill seems to leave quite the air bubbles in the system and makes it challenging to bleed. Hang in there

[Fidhle007]

I am running the 325 radiator with the external coolant tank. I've had it running with the cap off for quite some time but hopefully it just wasn't long enough?

[FredK]

spider hose to top heater core pipe?

I use the "understeer.com" procedure for bleeding, which is to rev the engine to like 2500 rpm and hold it until coolant starts to come out of the expansion tank.

[Bmjpv]

this works !

If you have a coolent pressure tester, fill the system, disconnect the radiator overflow hose on top of the radiator ,Bleeds off the air as you pump up the pressure .Make sure the heater is turned on . Maybe pricey to own a good Snap On Coolent Pressure Tester, but works evertime.!! Joe

[Brew]

Here's the procedure I use on almost every customer car and on my own S50-swapped E30 with 325 radiator and expansion tank:

With the engine cold, fill the expansion tank slowly with 50/50 mix. Try to keep the level up almost to the point of overflowing while continuing to fill slowly until you get to the point where the reservoir overflows and the level does not go back down. Then put the key on, switch the heat to max hot and the defroster vent open. Set fan speed to the slowest setting. Start the car and immediately rev it to 2500 to 3000 rpm and hold it steady for about 20-30 seconds. It helps to have a friend do this for you so you can check the coolant flow from the overflow hose into the expansion tank. After 20-30 seconds put the cap back on the reservoir and then return the car to idle. Road test the car and get it up to temp and then let it cool for a while before rechecking the coolant level.

[FLUTE007]

How many miles are on this motor you put in? Did you tear down the motor before hand to check for cracked head or faulty head gasket?

[Fidhle007]

103k on the motor and no, it seemed to run fine before it came out of the M3 so I left it as is. I'm going to try rebleeding the system again today, even though I'm pretty sure it's been pretty thoroughly bled and then I'll test it for exhaust gases in the reservoir if the problem persists.

[FLUTE007]

good plan.

[Fidhle007]

So here was an interesting thing I figured out, the overflow hose outlet (into the reservoir) was plugged. A 160psi air hose blew out something that looked like paper and at least now I have some semblance of circulation. The test came up negative for exhaust gases in the reservoir but I guess if the overflow hose was plugged it wouldn't be pushing the gases up there anyway. I'll run it for a bit with the newly opened up hose and see what happens and if I'm still having issues I'll run the test again.

[broke30]

To me it sounds like you have a cracked head. My old roomates s52 e36 ran fine with a cracked head for almost 2 years. We knew it was cracked but he kept replacing headgaskets because he didn't have the money for another head. Anyways he had the exact same symptoms you're having. I certainly would have rebuilt that motor or at least done gaskets while it was out. I did mine while it was out and found out I in fact had a cracked head. So I rebuilt a non-cracked head and did all the gaskets while I was in there....
Max

[So Live]

I had the same problem bleeding the system this last time. It took for ever. Some times it helps if you keep squeezing the top radiator hose to get some of the coolant moving or something. Mine would piss any coolant till i played with the upper rad hose.

Good luck man, i know how it feels to have a cracked head on a fresh swap car!!!! I got my car running for the first time and the coolant system was pressurized and exhaust out the coolant res. Good times...

[Fidhle007]

The problem seems to be solved! I guess having the blockage in the overflow hose was enough to backfeed any air left in the system and make it overheat. I've been romping on it fairly hard for the last few days with no adverse effects and no sign of the old symptoms.