How do i do a coolant pressure test?

[runGhostrun]

I have a small leak somewhere in my cooling system that i cant find. i have to add about a cup of coolant every few weeks. i cant smell or see anything. i decided to do a pressure test. i rented the tool from autozone.

how exactly do you do a coolant pressure test on an e36? there is no rad cap and all of the hookups are for a rad cap type of connection so i cant hook it up to the expansion tank.

do i need to buy an adapter somewhere or what



its a 94 325is with an s50 swap

[flyfishvt]

first find the adapter in ;that kit that is for BMW's. That adapter gets screwed into the expansion tank after you take the cover off.

Pressure tests should ideally consist of three separate tests. With the engine stone cold pump up the tester to about 15 or 20 psi and look for visible leaks. Once those are fixed pump it up to 20psi and let it sit like that for at least 2 hours and see if the pressure has dropped at all. If it drops a couple psi then no biggie. if it drops to zero or even 10 psi and you absolutely don't see any other leaks then you might have a headgasket issue. The second test HAS to be done with a stone cold engine. When you take a car to a shop for a pressure test they will always tell you to drop it off the night before so they can test it the next morning after it has cooled off.

The final test is not mandatory but its not a bad idea either. Screw on the tester and secure it to the car so it doesn't flop aound or fall off. Drive the car and get it completely up to temp and pressure. Probably about 10 miles or so. Then open the hood and see what the pressure gauge reads. compare that to the factory spec. if its way high you could have exhaust gas finding its way into the cooling system. If its way low then you either have a leak or you didn't drive it far enough to get the pressure built up.

[runGhostrun]

thanks that is helpful. but where do i find the adapter? would most shops have this?


edit: it looks like the harbor freight set has one that fits. i will try that.

http://www.harborfreight.com/radiato...kit-65053.html

[hpmaxim]

Autozone has a loaner tester system, but I'm not sure it has a BMW adapter. Other than that, Harbor Freight is an option. Don't forget the 20% off coupon. However, my experience with that tester has not been good. It seems to have a habit of leaking (and I don't mean the coolant system, I mean the adapter/hose/pump/etc).

[flyfishvt]

I have always used the one from Advanced Auto. Just make sure you open the case and make sure itsnot damaged. The pumps on most systems are plastic and tend to crack.

[mynameisBMW]

You could probably make one with a junkyard rad cap, a bicycle pump and an old bike tube. Modern bike pumps are pretty durable.

Cut the valve out of the tube, drill a hole in the rad cap, epoxy the valve in and then pump up to desired pressure. Use standard pressure measurement tools to check it.

[paniolo]

Autozone and O'Reily around here did not have the BMW fitting in their loaner kits. Just the old Detroit style. I need to check some other stores.

[runGhostrun]

harbor freight kit worked. it lost 2 psi in 2 hours so i guess that is acceptable. maybe the cap is bad

[BMWMPow3r]

well if you have a pressure bleeder (ussually 1/4" id hose)for your brake bleeding (around $50), you can make a setup like this. The fittings were bought at napa for about 10-15 bux. the motive power beeder comes with 1/2" npt x 1/4" barbed fittings already. I plumbed it into the 2 hoses (3/8"id) that clamp onto the thermo for the throttle body coolant, obd1 only. very easy and it also tests your cap, My cap was actually leaking. it beats over 100 bucks for a single use tester.

[paniolo]

well if you have a pressure bleeder (ussually 1/4" id hose)for your brake bleeding (around $50), you can make a setup like this. The fittings were bought at napa for about 10-15 bux. the motive power beeder comes with 1/2" npt x 1/4" barbed fittings already. I plumbed it into the 2 hoses (3/8"id) that clamp onto the thermo for the throttle body coolant, obd1 only. very easy and it also tests your cap, My cap was actually leaking. it beats over 100 bucks for a single use tester.

Good idea! On OBD2 cars you could use the top hose from the radiator to the expansion tank. I'm going to try this ... my autozone and other parts stores did not have an adaptor to fit our radiator on their pressure testers.

[BMWMPow3r]

the bleeder hose is smaller, so you will need smaller barbed fittings. and some extra bit of bleeder size hose to connect the t fitting. all can be found at certain napa stores. some will have to contact the wharehouse. just make sure you get the right size parts.

[flyfishvt]

Good idea! On OBD2 cars you could use the top hose from the radiator to the expansion tank. I'm going to try this ... my autozone and other parts stores did not have an adaptor to fit our radiator on their pressure testers.

That hose isn't just on OBD2 cars. Its on all 6 cylinder e36's.

All Advanced Auto stores have the same loaner kit that Ive used at least 3 times. That kit has the correct BMW adapter. The last time I used it the kit was a $180 refundable deposit.

[BMWMPow3r]

Good idea! On OBD2 cars you could use the top hose from the radiator to the expansion tank. I'm going to try this ... my autozone and other parts stores did not have an adaptor to fit our radiator on their pressure testers.

also remember with this method it may be more likely you'll add air pockets into the system. make sure to bleed and watch the temp gauge like a hawk afterwards

[paniolo]

T
All Advanced Auto stores have the same loaner kit that Ive used at least 3 times. That kit has the correct BMW adapter. The last time I used it the kit was a $180 refundable deposit.

No Advanced Auto in TX. 3 Autozones and a O'Reillys did not have the bmw adapter in their kits. Of course they all said they did on the phone, but when I drove there it wasn't in the kit and they just shrug their shoulders.

Edit: just because the stores around me did not have them in the kits do not assume your Autozone doesn't. The kits had locations for other adaptors, but they were not in the kits.

[motion]

That hose isn't just on OBD2 cars. Its on all 6 cylinder e36's.

All Advanced Auto stores have the same loaner kit that Ive used at least 3 times. That kit has the correct BMW adapter. The last time I used it the kit was a $180 refundable deposit.

+1 on Advanced Auto and don't forget to test the cap. Just my .02

[Brian 328is]

An idea is to use a portable air compressor, used to inflate tires & jump start cars.

Buy a T, and hook it up to the tire inflator.

or a manual bike pump, as someone suggested.

Watch the pressure gauge carefully on the powered compressor. With a small volume of air, pressure will rise quickly

Brian

[Brian 328is]

Just purchased this setup from a local hardware store, for 5/16" tubing, equal to the tube that goes from the radiator to the expansion tank . Total cost was $11.

Schrader valve allows manual or powered bicycle pump inflation.

Brian

[DotBeta]

One thing I always see not get mentioned in threads like this is if you are going to pressure test for leaks be prepared to fix that leak as soon as u find it. Pressure testing a small leak can turn it into a big leak in the blink of an eye, and if you're not ready for it then you'll be taking the bus until you can fix it properly.

[Guam135i]

Awesome