Radiator/hose querstions

[georgeramos]

I have a 71 with 1608 and Ive not been able to eliminate overheating for 2 years. The last "thought" I have is that the lower rad hose from the t stat was not the OEM one so where it had to make the bend onto the nipple maybe it was not seating right and was allowing a small leak to occur. i ordered a 1608 hose from Bayless but it is not long enough and frankly even with the bend at the bottom does not seat well on the nipple. So now Im thinking maybe I have a later year radiator...


can anyone explain the difference(s) in radiators as it pertains to the lower nipple on the stat side?

thanks

[azruss]

I ended up going to NAPA and looking for a hose with the right curves. I took my old hose. The hose was still not right, but didnt have any kinks in it and was able to seal at each end. I have a hard time thinking this hose being the problem unless you are certain it is not sealing on each end without any major kink in the middle. Tell us what all you have done to the system. Have you done a compression leakdown test.

[georgeramos]

Compression test yes, leak down no. Compression was 135 on all 4 cylinders. No sign of coolant in oil ever. Recored radiator, new water pump and thermostat with timing belt change, coolant flush Tee at heater hose, bypassed heater core as it was leaking into cockpit, flushed system with hoses as directed here, all seemed to flow.

Now I have NOT yet changed the temperature sending unit. I do have a new one but I could not get the old one to budge and I am very afraid of breaking it in the head. I also have not changed the temperature gauge although I believe it works.

So if I burp and burp and burp the system it all runs normally and properly for one to two drives. Next drive, overheats. Check the coolant tee and it needs some, not a ton but some. Then I have to burp, massage the hoses (particularly the stat to lower rad hose), fill, burp, burp, fill. same cycle. So there MUST be a leak right? The lower hose never looked quite right. Tried pressure testing the system myself but couldn't find a set with the proper adapter so had it done by a mechanic and while theirs did eventually work initially it didn't seal and poured coolant all over so it was very hard to tell if the lower hose was leaking. I had once noticed "wetness" around the inside perimeter of that hose so I suspect it leaks under load and lets air in right under the stat, where it would end up trapped anyhow I think...speculation. So I figure lets change it to be sure but the "proper" 1608 hose does not work, it is not long enough to reach the stat and it still does not seat properly on the nipple.

The car runs perfectly in all other ways. Run strong, idles very low but smooth and really kind of purrs along. If my fading memory serves when I had the radiator recored there may have also been a crack at that lower nipple which was repaired. I think now maybe the repair included cutting the nipple and welding it back on but slightly shorter on the horizontal portion where it meets the radiator...again speculation. or maybe there is a leak at the nipple itself although that seems less likely than the hose...

[DieselSpider]

Are any of the hoses collapsing?

Also do not overlook the hose to the overflow tank. If it collapses you can end up sucking air in from wherever the weakest connection is which may be itself or the radiator cap.

[georgeramos]

None of them are collapsing they're all pretty new. within 1.5 years if that's considered newish...

[azruss]

A couple of things come to mind. what radiator cap are you using. A cap with a bad seal can suck air in. One of the culprits for sucking in small amounts of air is the long heater tube flange that connects to the water pump. When i had similar issues, i removed that tube and sanded the flange flat and that stopped a small air leak that never dripped water. It sounds like if you can find that place where air sucks into the system, your problem will be solved. It could be in the recore as well. The issue is, you are sucking in air during the cooling phase without it leaking visible coolant. Does the level in the overflow tank drop slowly.

[georgeramos]

Im not sure about that Riss, ive only now started watching it and it doesnt seem to change but i will check it often and note the level. Hmmm, the heater tube flange on my 128 is currently leaking slowly despite sanding, new gasket and re seal. Wouldnt it be somehing if both my 40+ year old Italian cars were giving me fits for the same reason? I will check that too..

Please keep the ideas coming folks and thank you.