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Old 09-25-2022, 09:15 PM   #1
1st Gear Newbie
Join Date: Jun 2009
Location: Chicoutimi
Posts: 16
HELP: S52 cooling system high pressure

I'm facing a problem with my cooling system that I still can't figure out... Basically it's 1989 E30 swapped with a S52 OBD1 with 89 325i radiator. I frequently go to the track with it. 4 weeks ago, I was ending a sessing and the coolant level light was on. however, my level sender connector is not tight, so no big worries. I popped the hood, nd couldn't see well the level so untigthen the reservoir cap to see the level... pressure cme out a bit, level came up a bit, retighten it, everything was fine. (I know I shouldn't have done that but it's done...) Got back on the track for a solid 15min. I popped the hood and the system overpressurized itself and coolant had generously came out off the overflow tube. Also, one of the radiator hose had backed a bit! Note that the temperature was good, sub 200F. I let it cooled for a while, corrected the hose and I went back for a short session, no spill. Return for a longer one, 15min, and it spilled again! I thought the It was really a consequence of me opening the cap... while it was hot....

Drove it as a daily for 3 weeks without any pressure problem or any leak.

Had the coolant chemically CO2 tested and also pressure tested the system at 17psi for 12 hours. No CO2 and not pressure drop. Got it bleeded and put a new coolant reservoir cap. From there, the garage and I were thinking that every was fine.

Got back to the track last Friday and after the second session, a mapple cookie smell was present. Popped the hood and coolant spill was major, from the overflow tube but also from the cap itself! I also could hear a little leak from the coolant reservoir cap. At that point, I tought that it was the fit between my 33 years old reservoir and my new cap, so went back for a session. right after the session checked again and it spilled again, but now it was fuming from the radiator. I check correctly and the was a major leak form the waterpump shaft seal! The pump was replaced last years with a Hig hflow stewart pump. For this to happen, it's defintely not the reservoir, I really have a coolant high pressure problem...! After winding the engine, event when it was at idle, I coud see a significant coolant spray coming out of the pump pulley. Temp was at 188-190F during all the session. Outside temp was pretty cold, and I have a 188F thermostat. I have a VDO temp gauge. The OEM gauge was also looking just ok. so no overheating.

Drove home for 200 miles without the reservoir cap and level stayed perfect and no leak for the pump or anything!

From the CO2 test and the pressure test, my understanding is that it rules out the head gasket and a head crack. So what can cause this high pressure problem? can it only be a clogged radiator? However, the water temp was good... Also, this all started 4 weeks ago when I cacked open my cap while it was hot... I really have no clue!
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