Question about Cooling System

[katrina664]

I have an '87 MR2. Learning alot about the cooling system. Repeated airlocks.

I replaced the overflow tank cap with a flex cap from toyota, it was cracked adn antifreeze bubbled out of it.

The bleeder screw in the thermostat housing has been melted down and glued in place, we can't get it out, and it is not a tight seal as fluid keeps getting pushed past it into the overflow tank.

When I put the new flex cap on the man who is helping me (shoulder injury is holding me back, and having no clue too) insisted on capping that bleeder port and plugging the end that goes into the overflow tank.

He refused to fill according to specs and bypassed that bleeder as well, even though taking the hose off might have allowed for it.

It started having a really rough time once he'd plugged that hose.

He insists that the hose only goes into the overflow tank as a matter of convenience, that it has nothing to do with being a sealed system and that it will not hurt the car to have the antifreeze hit the plug and get pushed back into the thermostat housing.

Since I'm no mechanic, I hate to question him, as he is one, however he's never worked on an MR2 and disregards everything I've found here.

Finally today I begged him to hook up the hose the way it is supposed to be. I have a new thermostat and a new bleeder screw for the housing, if I can get the old screw out wihout breaking it.

Otherwise I will wait until I can buy a whole new thermostat housing, at least I can drive to and from work with it as it is. It hasn't overheated since I got that hose connected to the tank properly, but I haven't driven it but the four miles to work, where I burped it, and the four home.

If anyone could clue me in I would really appreciate it, I am about ready to save the unbelievable amount of cash it will take to have the toyota dealership do it if I can't get some sort of evidence here to share with this man, who comes at a cheaper rate.

Thanks alot.

[55mr2]

Your machanic is an idiot. You can't start arbitrarily plugging coolant hoses or disconnecting them just because you don't have a clue what they are there for.

He needs to follow the BGB on filling and bleeding the cooling system for a reason. The car's cooling system is considerably different than a front engined car because the high spot on a "normal" car is the filler cap. That way all the air in the system will migrate to the highest point and eventually vent out by itself. As long as you keep the overflow tank filled, the system will maintain itself free of air.

On a mid-engined car, there are 3 high spots, kind of like a sideways 3. Two are in the frunk and 1 at the rear. You need to bleed all three to remove any trapped air. If you don't, your cooling system will not do what it is designed to do and you run the risk of doing some serious damage.

Because of all the pipes and tubes, etc, the amount of coolant required to fill your system varies as the engine heats up and cools down. The overflow tank is meant to allow excess coolant to escape when there is too much, and to replenish itself when the system expands and needs more coolant.

[Ben]

Do you have a pic of the housing that melted? If a mechanic feels that bypassing something is better than having it routed correctly, I would think of finding a different person to fix it.

[katrina664]

I'll try to get a pic. It's the bleeder screw on the thermostat housing. When I bought the car that screw had been melted and jammed in and possibly glued. It has trashed the seal, and therefore coolant is getting pumped straight past it and into the overflow tank, based on what I could find on a link I found here.

I have the new bleeder screw and gasket, but we can't get the old one out without damaging the housing until we can get it into the shop and pull the thermostat housing itself, hopefully loosen it from the inside, though I may have to buy the 130 dollar housing.

I have a new thermostat for it, too, ordered it from toyota according to the month the car was made. If we can get that screw out, put in the new thermostat ( I think the previous owner just bought one at Schuck's if he replaced it at all) he has printed out the proper instructions for filling and promised me we can do it according to specs.

What happens with it hooked up properly is fluid gets pumped past that damaged bleeder screw on the housing and into the overflow tank and right out onto the ground from there. With it stopped up as he had it, that stopped and the car was able to pull from the overflow tank as needed, but it ran kind of rough and scared the hell out of me because I THINK IT IS SET UP THAT WAY FOR A REASON, AND NOT JUST AS A CONVENIENCE FOR BLEEDING AT THE THERMOSTAT HOUSING SCREW.

He thinks they have it hooked right into the overflow tank so when you bleed there it goes into the overflow instead of you having to hook up the little hose.

I'm no mechanic, but I have driven toyotas for 20 years, have great math skills and am continually learning. If i didn't need shoulder surgery I would attempt this stuff by myself. Ulitmately I think I am going to have to limp it into a toyota dealership and pray that they can fix it.

I'm really nervous about having it capped off in between the thermostat housing and the overflow tank, he assures me this will not hurt it at all. If it won't hurt it, why'd they design it that way?

It's such a cool little car, I guess they didn't make too many T-tops in '87. Has 150,00 miles but just had the head redone before I bought it, unfortunately I bought it from a guy who got it at auction (it had been abandoned) and he kinda slapped it together and not according to specs.

It's a sweet little car and I don't want to give up on it, not to mention that I have a limited income with this damned shoulder injury and can't just play around. I wouldn't dream of selling it as fully functioning and ripping someone else off. (I paid 1200 for it, despit rust damage around the wheel wells, didn't know it had been auctioned until I signed the transfer of ownerhip, dude didn't even have a title.

When we first drained the coolant to flush the system (it was already overheating) SAND came out. I suspect it was abandoned after someone blew the head, filled it with river water and then gave up. Auxilliary fan doesn't kick it, that may have been what happened originally. We hard wired it until I can pay for a new switch.

[Ben]

Have you looked on the For Sale threads here for a thermostat housing?

[katrina664]

Nope, I will give that a shot! Another cool benny to this site!