QuestionQUESTION: hi howard,
i have a 62 tr3 that runs hot. i changed the therm. & even took it out. the water pump seems fine, radiator seems to flow ok, not burning anti freeze. any ideas? thanks for your help! jim
ANSWER: Hi Jim,
When diagnosis a problem you can't assume things. The only method is to test and use standard tests.
Do this little test. With the engine cold, fill the radiator to the brim and leave the cap off. Start the engine and watch the coolant level carefully to see if it rises quickly. (The level will raise very slowly from heat expansion but must not raise right away) A rise in level right away is an indication of a leaking head gasket. It is only a first preliminary test. There are a couple of 100% sure tests. One is with a CO/HC annualize by sniffing the coolant in the radiator for CO/HC. The other is within the average persons reach if you have compressed air available. Purchase a fitting from a automotive parts store that fits in place of a spark plug and will adapt a standard air hose. Tool trucks that service repair shops usually have them if you can't find an auto parts store that does. They are not expensive. Put # 1 at TDC and put the gear in 4th gear and the hand brake on hard. Keep everything out of the way ot front and in the rear of the car because if it is not exactly on TDC and the hand brake is not up to par the car can lurch when line pressure is applied. With 100+ PSI applied to the combustion chamber open the radiator cap and note any raise in coolant level. It will only take a minute if there is a leak. Do the same on the other three cylinders. (This is a good test for either valve leakage also, just listen in the carbs and listen at the tail pipe, if any hissing is heard you have a valve leak also, nothing to do with overheating)
This pressure test is good for even the slightest leak that may even not cause overheating. No raise in level = no leak at all.
Don't run without a thermostat. Fan is attached to the crankshaft so that is not a cause. Radiator could be partially stopped or you could have a lower hose coming apart inside and stopping sufficient flow.
A temp gauge on the upper and lower hose will tell if the radiator is doing it's job.
Big question is does your thermostat have a sleeve to close off the bypass? if it has a plain thermostat like a Chevy has that may be your problem.
Let me know
Howard
---------- FOLLOW-UP ----------
QUESTION: hi howard,
i ran the engine with radiator cap off, expands slowly. i pressure check the radiator no leaks, no steam from tail pipe,no smell. compression thest is 140psi across cylinders. i think the next thing i'll try is change hoses, rod out radiator unless you know of something else. i'm not sure what you mean about a sleeve for by pass. thanks for your help..jim
AnswerJim,
Remove the thermostat and look at it. If it looks like any older Chevy thermostat discard it and look inside the bore where the therm. fits and you will see a port in the wall and one or more hoses connected to the outside where the side port is. This is a bypass of the radiator for warm up. If a standard thermostat is installed a good portion of the heated coolant will just run back through the engine and not go to the radiator. On the thermostat should be a large balking ring to block off this side port when the engine warms up. At the beginning of summer I use to get a lot of them in the shop with a standard thermostat in which was unnoticed all winter but became a problem as the weather warmed up. TR-4s had the same problem.
Your tests so far look good but don't leave any stones unturned. Your radiator core could be a problem but it may not have tubes, as the old ones had a honeycomb type core. Your local radiator shop may be able to do a flow test and maybe boil it out if necessary.
Before you go to that expense, be SURE the timing is correct and the advances are working and that your SUs are a hair on the rich side by the small lift pin test before you go to the trouble and expense of the radiator test/work.
Let me know,
Howard
