C4 Coolant Level Issues
Thread Starter
Heel & Toe
Joined: Sep 2019
Posts: 17
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C4 Coolant Level Issues
I have a '92 convertible with 50K on the clock and recently noticed a small spot on the garage floor under the nose in front of the passenger side front wheel. Upon further inspection it appeared that it was a bit of coolant coming from the coolant recovery reservoir. I checked it thinking that there might be a crack or a bad hose connection but there doesn't appear to be any. What it seems to look like is that it is over flowing through the filler cap as the volume of coolant in the reservoir is high even when cold. As I understand the way the system is supposed to work, the surged coolant is supposed to be drawn back into the system by vacuum when the engine cools down taking things down to the "cold" level in the reservoir. I used a suction bulb to draw down the excess coolant in the reservoir to the "cold" level and deposit it back into the system at the filler cap on the radiator surge tank. I did this but noticed that the recovery reservoir was still at the high level where I started when suctioning out the excess coolant. I pulled about 1 quart of coolant out of the recovery reservoir. The color looks very fresh as it should. I do not get any alerts on the dash about low coolant or "hot". Everything seem to be fine including the gauges for temps.
Any ideas what might be going here?
Any ideas what might be going here?
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
I used a suction bulb to draw down the excess coolant in the reservoir to the "cold" level and deposit it back into the system at the filler cap on the radiator surge tank. I did this but noticed that the recovery reservoir was still at the high level where I started when suctioning out the excess coolant. I pulled about 1 quart of coolant out of the recovery reservoir.
Any ideas what might be going here?
Any ideas what might be going here?
I'd guess that you suced out some from the overflow tank (ahead of the front wheel) and as you put it into the surge tank (pass side below the windshield), it filled to the fill "neck", then simply ran down the ~1/4" hose, right back into the over flow tank....putting you right back where you started. IIWM, I'd draw from the overflow tank when the car is COLD, down to the COLD level....then run the car and monitor for proper operation. Re-check when it's cooled. If the exchange between the surge tank and over flow isn't happening correctly (as you described above) then you need a to "radiator cap" on the surge tank.
Thread Starter
Heel & Toe
Joined: Sep 2019
Posts: 17
Likes: 0
C4-Coolant Level Issues
Thanks for that interesting theory, I'll give it a try. When I suctioned out the reservoir I got about 1 quart of fluid but still did not get down to the "cold" level. When I dumped it back into the surge tank up top, upon further inspection I noticed that the reservoir was back to where it was before suctioning. So your estimation that its just running right back down the hose to the lowest level sounds correct. Fluid finds its own level at the lowest point. I haven't changed the coolant in this car and it is as purchased from a year ago. I would expect that if this was an over fill issue I would have picked up on it when inspecting the car or would have noticed it over the past year with any spotting on the garage floor after use. This is something that has just appeared. I'll suction the fluid out once again and drive it a bit to see what gives and if the fluid stays to a reasonable level in the reservoir without overflowing through the cap. When I first opened the surge tank cap and refilled it with the suctioned fluid the level came up just below the filler neck. I have a set of FSMs and I believe this is the proper level.
Last edited by 92pologreen; Mar 22, 2020 at 01:09 PM.
