Car = 1991 745T

Replaced my old, cracked coolant expansion tank/bottle with a used one from local Volvo mechanic. Both caps are rated at 150 KPa, but have different threads. Now that the system is holding the pressure that it should, there is a trail of coolant down the driver's side, rear of the radiator after it cools down. Also leaves a small puddle by morning. Did not have this problem with the old, cracked expansion tank.

With either the good tank or the bad one, the temp gauge reads the same. So, I was wondering if I could sort of put off having to diagnose and fix this now (very bad time for me) by simply putting a 100 KPa cap on it until I am able to fix it right.

I know the turbo cars, like mine, have a thermostat that opens at a higher temp then the normally aspirated ones, but wouldn't 100 KPa work? Just for a while?

I feel kind of between a rock and a hard place because I really don't like running an old cooling system at pressures as high as 150KPa, but, on the other hand, have extensive natural/physical science edu in college, so know why the Volvo engineers specified the higher pressure cap on the turbo. Keeps the coolant from boiling off at the higher temps the turbo operates at.

Still, have any of you run a B230FT with a 100 KPa cap and had success with it?

Thanks guys. While you were posting, I took it out, about 4 miles each way and looked for the exact source of the leak with insp. mirror and light upon return. Had been hoping for seepage past poorly applied hose clamp, but no such luck. There is a small crack in the driver's side radiator tank, on the inboard side of the base of the big fitting for the driver's side hose (to thermostat housing). Seepage is just that for now, but decided that it stays parked for its own good until new parts arrive sometime next week.

Steve R. Thanks for mentioning the heater valve, I'd have forgotten about that if you hadn't brought it up. Will order one of those too so can do it all at once.

Will also buy 75KPa cap. Do you think it will be enough to prevent any danger to the cooling system or engine here, in Florida, in the summer with up to three people and three Great Danes on board? In other words, carrying heavy load, hot load (dog's normal temp is about 102 deg.) on hot Florida day with A/C running at max?

On the up side, all the hoses are virtually brand new :)

One more thing to check while you're looking at all the cooling system bits - the 2 short water hoses on the oil filter adapter. They tend to get splashed with oil when the filter is changed, and I've heard of few instances of them letting go.

- Brian '93 945T

Should be. If it isn't and you start seeing overheating (high temp on the gauge, overflow on the expansion tank) up the cap to 100kpa and try that. If you hav ethe same problem again then go with the hard core 150kpa, but I would only use that if absolutely necessary.

I think of more importance in a hot climate is the t-stat you select. I think there are tropical climate stats that will open sooner to prevent overheating issues in hot climates with teh AC running. If you really start having issues you might also check your aux electric fan. In the early models its simply temperature actuated, but in the later models it actuates when the temp passes a point OR when the car is running AC and going slower than 15mph (to prevent overheating at idle with AC).

I'm actually doing a lot of this work myself tomorrow. Have to replace the hoses, exp. tank, valve, radiator.

good luck,
rt

Dude I wouldn't run a 150kpa cap if you paid me. The system's components may be able to take that kind of presdsure (over 20psi), but I have no guarantee on the old hoses. Regardless, running such high pressure us stressing your system and just ASKING for a failure.

Get it off, NOW. Go to fcpgroton.com, buy a 75kpa cap (black), and replace teh existing one with that. 75kpa is PLENTY for just about anything you plan on doing, and with only a 10-12psi cap you know the cap will overflow before the radiator explodes. With a 150kpa cap it is HIGHLY probably the radiator will destruct before the cap lets coolant run over.

-rt

I spoke to IPD about this: they recommend a 75kpa cap with all replacement radiators for the reason that the 150kpa cap is rated for all conditions, including summer heat with a/c in Phoenix and most people don't need that. Note, however, that if pressure reaches the rated level, the cap will release and coolant will come out. Your problem is different: the radiator is failing. Your original plastic radiator has reached the end of its life and you definitely need a new one ASAP since you risk catastrophic loss of coolant (see the FAQ). The typical failure mode is a small crack followed by sudden and massive failure when the pressure/temperature reaches a high enough level. Every spring this board sees a spate of "help: lost all my coolant" messages due exactly to this problem. The plastic/al radiator is in fact a superior design, far more resistant to corrosion than copper/brass, and suffers from only one flaw: the plastic lifetime is reliably about 8-10 years max.

If you are short of cash, drive with NO radiator cap for the time being. Buy a new PL/AL radiator from FCPGroton who have the lowest prices.

And I can also guarantee that your heater water valve is aging and close to failure as well, being made of the same plastic. Regrettably, you are close to requiring a new radiator, valve, and all hoses ASAP.