Hey all, new to the forum , I recently got a 1993 Lexus sc300 and I have an intermittent bubbling after I shut the car off, mainly after driving with the ac on, car doesn’t overheat at all, runs strong, new radiator and cap, supposedly head studded and new timing belt, I don’t think it’s a head gasket because the coolant is nice and clean, loses a little bit, I’m assuming to overflow, and the oil is perfect , no fuel smell in coolant either , could this just be a faulty new cap, or should I try and re burp the system? Help I’m lost !! 😂

 

You’ve most likely got air coolant system. Try burping it again. If it comes back, you’ve got something causing air to enter coolant lines.
if Not running hot you can decide to live with it.

if coolant leaking, keep searching for where this coming from and address it. In meantime keep topping off.

get or rent test kit to check for exhaust gases in coolant system if you want to rule out causes like head gasket or warped head

 

is there a procedure to bleed all the air out? It seems to push the coolant out only when I’m driving, or after I park it from driving with ac on for a while,car also has no fan shroud but doesn’t over heat, but maybe that’s causing the radiator to be hotter than necessary?

 

hi. If you have $35 or so I’d recommend getting this from harbor freight

PITTSBURGH No-Spill Radiator Funnel Kit

it will make your life easier again and again if you do much work on cars. YouTube will show you cheaper ways to do it with a funnel and tape but things easily get messy those ways. Search YouTube for “getting air out of car coolant system” and things will come up. Watch a few to make sure process and rationale behind it is clear. Funnel kit has instructions too. Other similar kits available amazon too for similar price. Lisle maybe

if you’ve got air being forced out of overflow tank you either added too much coolant to system and when it heats up and expands it has no where to go but out of top of coolant reserve tank. This can also happen if your thermostat fails closed or air bubbles blocking passage of coolant near thermostat. Here, Your car will run hot—upper hose gets hot as hades while lower hose almost cool. Getting air out can solve this if that’s the problem. Since you not overheating, this probably not going on.

lack of fan shroud will reduce cooling efficiency of radiator fan, but not too badly

in general, top off coolant when engine cool and do so by adding into overflow tank and
keeping Between hi and low levels marked

GAsc300

 

So I think the head gasket popped, I believe there’s oil in the coolant? It overheated while I was sitting, any other causes for the oil in coolant?

 

you gotta figure out what’s leaking and where it’s from. Head gasket issues likely create internal problems, not spontaneous leaking. You have a lot of unknowns on newly purchased 30plus year old car. Start figuring things out bit by bit and attempting to solve cheaply or think about more as you collect data.
Rent exhaust in coolant test tool and buy testing fluid from car shop like autozone or oreillys or etc to rule out or in head gasket or similar serious engine issue. Autozone rents one out called

OEMTOOLS Engine Combustion Leak Detector

There are Other things to consider after you do previous suggestions