I've read on here with people with a similar problem. I have a 1999 TL-P and recently replaced the head gaskets, water pump, t-stat*, t-belt, tensioner, radiator, radiator cap, etc. The car runs fine at highway speeds but, after a trip (maybe 30 min on the freeway) when i come to a stop the vehicle begins to run hot. So far it happened maybe 3 times but i never let it get to the red zone. It looks as if the radiator is pushing coolant to the overflow/reserve tank but its not bringing anything back into it causing the radiator to loose a lot of coolant and thus overheating. This only happens at a stop, when i hop back on the freeway it begins to cool back down. I have recently changed out my radiator cap to a Acura OEM cap, both fans are working**. I have turned my engine off and let the engine cool down and poured the coolant that overflowed back into the radiator which seems to solve the problem temporarily. Also when i remove the radiator cap the pressure gets pushed through the overflow tank causing it to fill up more. Anyone have any insight on what might be causing the coolant not to come back into the radiator from the reserve/overflow tank? Thanks

Cliffs notes:
* I am currently running an aftermarket t-stat. This is what I may change next as we all know brand new part fail, and it may be sticking
**In case you missed it both fans do turn on.

 

In your case it is more likely the thermostat. If you got overheat but not overspilled, then it could be the fan or the fan switch. Try to remove the thermostat, drive without it and see what happens. it s better running it cool than running it overheat, and fix it latter when you could pinpoint the problem.

 

Im thinking that aftermarket t-stat is not liking the TL..OE always on that part
iirc it has some mark for direction it sits too--gurus confirm?

on res tank operation:
first look inside its cap- is the black rubber hose FIRMLY attached to the cap?
that hose makes the whole transfer back and forth happen and it likes to slip off!
cap must fit secure on res tank too

there is not a lot of fluid motion when car is running normal--happens at shutoff when engine temp rises at shutdown-system sends fluid to res overnight,
then as engine cools it suctions what it needs back into rad

STOP opening the rad cap hot!!! cool rad with house water hose water, engine running!
-sucking coolant from the engine block makes things hotter inside, the temp guage is external coolant temp, not internal

You are a major candiate for serious 2nd degree burns to the upper chest!!
and you are not helping the situation removing the pressure and forcing fluid movement

DO a normal BURP of the system, heater on full hot, cabin fan running
make sure there is not trapped air messing with you
then when its dead cold again in the morning- rad full to neck, cap seal good and on tight
res bottle at max COLD line = not full!! at proper line so it has room to work

drive and see what it does

often- heats at lights and cools with driving is clogged rad or bad water pump
Ck for pinched cooling hoses too
Plus you had a major overheat situation that caused the work to be done- correct?
so there may be something still on the original problem?

on rad fan operation
driver side runs as needed while sitting at light?
driver side runs several to 15 minutes after shutdown? = bad fan sensor, not running when you need fan,,, and trying to kill battery too!
AC on causes both fans to run, but ac adds load and heat to system

 

I realize you already replaced several of the parts mentioned, so double ck the new parts are actually working!
wouldnt be the first time............

were the heads ckd for straight- no warping?
sent them to a machine shop to skim off a little to make them flat?--they warp when overheated really bad- like it sounds happened to you before

ck oil for any signs of coolant getting in there
if the heads are not flat, the new gaskets wont seal

 

ck the res cap carefully- remove the tube and look for crack on connection that would allow air

 

i knew i would get flamed for saying i open the radiator. haha Dont worry folks, i make sure its cool enough to touch before i open it. im thinking its the reservior tank thats causing the problem since its not sucking coolant back to the radiator. It looks a little iffy and has a hole in the cap and the hose thats attached to the tank to the radiator is not stock. i bought the car from the previous owner with blown head gaskets and did the repairs myself at my friends shop. had the heads resurfaced since they were slightly warped.

 

needs a air-sealed system from rad to res bottle
ck out that more,,loose clamp somewhere
wrong hose size
and inside the caps hose--broken connection at all?

coolant forced to res bottle sounds like exhaust pressure into engine...

 

the reservior is def not pressurized as there is a hole in the cap and the hose is not 100% sealed. i saw on a parts diagram that there is an elbow that goes on the cap that is no longer there anymore. should be less than $50 to order a new set.

 

That's what I think as well. It's a classic symptom of a head gasket. There are lots of ways to ruin the job; even the surface finish of the head and block are critical.

 

thanks for everyones input. Ill let everyone know how it goes when i get the parts

 

head bolt torque is critical

ck parts store for a universal overflow tank system

 

so i did some diagnosis and the radiator fan motor is out. I may replace with an aftrmarket slim fan or try and pick up a Used OEM from a recycler.

 

but you said it ran for 10 minutes after shutdown?
does it test bad when jumper wired?- spins rough or slow compared to passenger side fan when spun by hand?

get a temp sensor too,,, so its really fixed for your efforts
aftermaket slim fans do a great job, not sure mounting on the back,
but you can always by a `pusher` one and go in front of rad- like many project/race cars do
in theory it will get better colder air going thru too = bonus~

 

so i changed the fan today that seemed to have failed in the passed few weeks thinking that was the culprit of the problem. but after about a 30 min drive it still boiled over and overheated. what a fu*kin headache! im gonna change the reservior tank next. if that doesnt work im gonna light it on fire...

 

also, I pressure tested the system to 16 lbs and it holds pressure. It has a new Waterpump, thermostat, radiator which were changed when I did the head gaskets.

 

swap out that aftermarket t-stat for a dealer one- TL seems to be picky about that part

while its running normal, the res bottle has no interaction with the engine - only when temp spikes suddenly at shutdown and no more water pump pushing cooling fluid thru rad,,sensor picks up rise and turns fan on a for short time 1-2 minutes

then in the morning when cold,, and rad level down from the push,,it suctions back what it needs to top off rad

from there- it doesnt seek constant transfer during operation,,
at hot shutdown it will do a little transfer again--durring your errands for example, and pull back what it needs

A new aftermarket res bottle wouldnt hurt to try- iirc you have a crack or issue on the res cap? thats got to seal to bottle and the hose inside to it, or rad just gets low and never gets to suction back,,causes air in system which can get behind t-stat and fool system guage and run hot

please detail HOW it gets hot--runs perfect just below half until ....
or gets hot to 3/4 right away and goes up from there....
in town on freeway ac on off
Need details on this one!

 

new rad cap yet?
new res hose to bottle from rad?

 

changed out the thermostat with a OEM one and burped it. Both fans came on etc. Did a 30 min test drive and it ran normal at freeway speeds. Once i exited the freeway i let the car sit at idle for about 2-3 min and the temp started to rise slowly to about 3/4. I popped the hood and the reservoir tank was again overflowing. although during this time the fans were not on while the temp gauge was rising. Could it be a bad coolant temp sensor or bad fan switch? Im going to test the radiator for hc's tomorrow to see if the heads are cracked, it may be leaking pressure into the cooling system. I've talked to a few of my buddies that own a shop and they told me my bottle and tube are fine, as long as the pickup tube is submurged in coolant.

So far I've changed the following parts/work done:
Head Gaskets
Heads resurfaced
Waterpump
Timing Belt & tensioner
T-stat (Twice, now haw OEM)
Radiator
Radiator cap (twice, now haw OEM)
Rt upper engine mount
Drivers Side Axle

 

fan temp sensor/fan switch iirc is on thermostat housing for 99s?
you would know by now!!

jumper that to test, but if you know the fan(s) work from jumper wiring them,
its probably bad and what started the whole overheat prob
may work sometimes?? but not when needed

Sure sounds like blown head gasket,,,
might need to retorque the head bolts after 500 miles? thinking of the old chevy, and how some here find intake bolts loose after its been off
Now I use `gasket cinch` on bolts and they stay right!

Engine gurus- retorque required? or maybe nicked a gasket on install, or `helper` missed a piece of gasket on block side during prep?,,not the first time thats happened- micro sized crud stuck on, or a blade nick to surface...

the radiator ~sniffer test~ for carbon monoxide in coolant will tell the truth

 

res bottle- must be good connect at rad attach point for hose, and THRU the res cap into the fluid
if a crack anywhere or loose fit allows air to get in - the system stops transferring
If the hose falls off- which it likes to do, no transfer

 

head bolts are definitely and concern here as well. when i pulled off the head when i changed the head gaskets before two of the bolts snapped when i removed them. so i replaced the broken ones and reused the old ones. Im thinking the others were stretched and should have been replaced as well. The heads were pressure tested and resurfaced at that time as well. So me and a friend of mine are thinking the head bolts need to be changed out? i know i should have replaced them in the beginning to cover myself but now its biting me in the ass

 

Are you noticing loss of fluid other than it overflowing? Any color smoke in the exhaust?

 

sorry didnt have time to read the thread....in a hurry and just posting my recent experience....

the radiator was not taking any fluid from the reservoir....and was causing overheating (slightly)....

The problem was: the tube from the cap of the radiator had fallen inside the reservoir and hence it wasnt able to suck the coolant....see if yours did the same....after I plugged the hose back on and took the car for a drive the reservoir went from a little more than max down to almost empty....

 

I mention that one in nearly every other post on overheat--
ck the little tube inside the res botttle!

 

the reservoir bottle is not an issue. it is working as it sucks coolant from there as the engine cools down

 

its doesnt SUCK fluid from rad,
its there to catch what fluid the rising pressure in system pumps overboard thru the pressure relief part of the rad cap,,the spring in cap

it SIPHONS back to rad once cooled down,,if the hose-cap- line are all tight and working

 

I apoligize, let me rephrase that. from my understanding the reservoir is there for when the coolant over flows from the radiator when the pressure goes over 16lbs(1.1) and when it cools back down the radiator sucks the coolant back from the reservoir. otherwise, if there was no reservoir the radiator would crack. In no way is the reservoir part of the pressure of the cooling system right? im thinking there is excessive pressure from inside the cooling system coming from somewhere.

 

yeah it is- the exhaust pressure entering coolant port where the head gasket is blown !

in the old days there were no res bottles, and cars carried canvas bags of water on trips~
it was normal for the rad to run slightly low and stay there, adding water was standard procedure

the TL system needs the unbroken seal in the sytem so it can suction back as needed

 

to clarify: the res cap can have a vent
BUT the part that runs from hose to hose must be secure-leakproof

 

Bad headgasket job..

 

my guess is because i was too cheap to replace all the head bolts, and instead reusing them... its an expensive lesson learned. I'll let everyone know how it goes when I get around to pulling the heads off again and replacing them.

 

I don't think replacing head bolts would make a different, it's either bad gasket or need to resurface the heads to make it level. Inspect your block surface too, see if any imperfection.

 

he already had the heads surfaced
and iirc found a few head bolts stretched or otherwise damaged from the overheat that led to head gasket failure
thus OPs theory of elongated bolts dont hold correct torque = easily blows new head gaskets when torque reduces

 

correct. two of them were changed when i took off the heads originally because the head of the bolt snapped upon removal. i pray that is the culprit of the issue here

 

for a head bolt to snap off its top,,something is wrong with it for sure

 

Let us know what the outcome when complete