Boiling coolant?

[ceningolmo]

Ok... so my dad bought my green Q. And, it has run reliably since he has owned it. However, today, there was an...incident.

He stopped to have the car washed at one of the nicer local places. They left the car running while they vaccuumed the interior before washing it. Its about 90 here today, so a little warm. Apparently the car started to leak massive amounts of coolant just as the guy was pulling the car around to go through the wash. He shut it down and took the car through the wash.

When he got the car out the other side he turned it on and pulled it off to the edge of there lot and called my dad over. They popped the hood and found the coolant in the overflow area was at the very top of the canister and was literally boiling. As it sat there idling it boiled over the canister edge and it leaked coolant again. Apparently this is the same spot it had leaked from the first time.

My dad hopped in and took the car to a mechanic he knows (about 100' up the street). The mechanic looked at it, checked the temp gauge in the dash (which never moved at all) , filled the over flow which was now nearly empty of coolant. He told my dad to keep an eye on the coolant level and the temp gauge and sent him on his way.

My dad then drove the car for a couple of short (about 5 minutes) trips near our house. He shut the car off at the end of each trip and checked for any leaks under the car and found none. The temp gauge remained solid, the coolant level in the over-flow was low both times. I just helped him fill the over-flow again.

Ok...so, whats the deal? How does the coolant get so hot without the temp gauge going off the charts? Anyone experience this before?

[96Qowner]

Bad/sticky thermostat? And Q45tech has said that the dash temp gauge is nearly useless - by the time it moves noticeably, the temps are already WAY too high.

[ceningolmo]

Tstat is cheap and easy...so, I am going to replace that just because it seems better to do it that not do it. Does anyone think that replacing the waterpump is a necessity? It has not been leaking coolant previously, and there does not appear to be any coolant on or around the area of the waterpump. So, if it is bad it is not leaking the way it did on my Silver Q and the way I have heard described by others.

Other than waterpump and tstat, any other primary suspects? I have not done the under-plenum job. However, I looked with a flashlight when I was refilling the coolant after he brought it home and there did not appear to be any leaking fluids under the plenum or in that area of the engine. Looks like all the hoses are intact.
Modified by ceningolmo at 8:50 PM 5/30/2006

[ddrumman]

This a direct quote from Dennis."The temperature gauge only works IF the coolant is full!!"

[ceningolmo]

So, I can assume that driving it right now is not safe for the engine. The question is recommended solutions.

TStat should be done for sure.Waterpump...maybe, maybe not?Radiator...any reason to assume this is part of the problem?Hoses...too much heat likely to damage the hoses?

[Jesda]

Have the radiator removed and cored out. Shouldnt cost more than $120 with labor and coolant. Of course, at $200 you can just buy a new radiator and install it yourself.

Replace the two caps with Nissan OEM radiator caps.

[CrimsonQ]

too much water in the mix?

[Rex]

In previous posts Dennis (Q45Tech) has recommended changing both oil and transmission fluid after an over heat.

[superuber]

you keep saying you filled the overflow tank. Have you checked the level in the engine? pop off the cap (when its cold) and fill it up. You will not get an accurate temp reading if the coolant level is low in the engine. The temp sensor has nothing to read. That coolant that keeps disappearing in the tank is going somewhere.

http://community.webshots.com/user/neheadsuperuber

[ceningolmo]

I needed to wait a little while until the engine was cool enough to pop the radiator caps before filling. We filled a couple times in the overflow...but, last night, I took the radiator cap off and filled it from there. It took about a quart of water, maybe a little less.

I am going to do a new thermostat for him today. I will have him bring it up to our local BG shop for a transmission flush since he was planning to do it anyway. Will get an oil change while he is there.

Is it worth doing a coolant flush before changing out the radiator, or should I assume it is bad and not waste my time? And, sounds like no one is worried about the waterpump...can I assume that is not the problem?

[Jesda]

I've never seen a water pump fail without making noise or dribbling fluid first. Exception: On another car I had one burst into pieces upon installation. That was highly amusing.

It might be good preventative maintenance to replace it anyway while you have the fan off and the radiator out.

Flushing helps if it hasnt been done in quite a while, but preferably do it after replacing/coring the radiator.

[superuber]

I've never seen a water pump fail without making noise or dribbling fluid first. Exception: On another car I had one burst into pieces upon installation. That was highly amusing.

It might be good preventative maintenance to replace it anyway while you have the fan off and the radiator out.

Flushing helps if it hasnt been done in quite a while, but preferably do it after replacing/coring the radiator.

Right on!

[elwesso]

Itsprobably the Tstat.. When I first inspected the green car i suspected the Tstat because the upper radioator hose would get warm as normal but it didnt have good pressure.....

[DrewQ45]

Itsprobably the Tstat.. When I first inspected the green car i suspected the Tstat because the upper radioator hose would get warm as normal but it didnt have good pressure.....

That reminds me. With the car warmed up, feel the bottom and top hose on the radiator. If there's a big temperature difference it might very well be the Thermostat.

[ceningolmo]

Thanks for all the help guys. Here is what we did.

I replaced the thermostat. The old one didn't look bad... but, that doesn't mean anything.Did an oil change and oil filter change.Did a transmission flush with all fresh transmission fluid (this was at my local BG shop...they did the full BG Flush rather than me doing the 3 quarts at a time method).Did a coolant flush when I did the thermostat. I emptied the radiator and the overflow. Filled with a mix of coolant and distilled water when I put everything back together.Replaced the fuel filter...of course that wasn't related in any way to the other stuff, but it needed to be done.Fresh tank of gas and a BG44K treatment.

My dad took the car for a couple of 15-20 minute drives at relatively low speeds (don't think he got above 55mph) and everything looked and felt good according to him. He checked coolant levels after the drive and everything stayed right where it should be.

For now I am going to forego the new/re-cored radiator, though I will keep that possibility open. If anything seems unusual in the next week with the temps I will do the waterpump (just to be safe) and a new radiator.