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· Member
88 Posts
Discussion Starter · #1 ·
I just went through a bit of a mess trying to figure out why my Opel was overheating. Here it is for anyone that has similar problems:

Symptoms and steps:

Original engine ran but had only 60 lbs compression in #4 cylinder - rest had 140+. Wet testing #4 did not improve the compression and valve train was checked while running and appeared to be functioning correctly. Re-adjusted anyhow and tried again. No improovement. Also no prefire or backfire. Never ran this engine long enough to get very hot. Assumed the head or valves were damaged/worn.

Replaced with rebuilt engine. Water temp climbed nicely to 180 and then just kept going - leveled at 280+. so...

Checked timing (on the mark), carb (a bit rich and definitely not lean), Radiator (full and no leaks), and verified all hoses were good (all are new).

Removed thermostat and ran without. Same result.

Spit on water outlet (my personal version of a guage check) and spit danced like it was in the skillet! Guage was correct if not low.

Crapped my pants (now Im wondering how many minutes I have run this thing this hot and whether the head is damaged).

Checked water pump. Seemed to flow OK but replaced it anyway - visible electrolosys in return passage.(second clue) Ran again with new pump and no thermostat. Same problem.

Removed pump and used a coathanger and high pressure hose to see if there was junk in the head or block. No garbage came out and the engine seemed very clean.

removed both radiator hoses and ran water from top to bottom. Water flowed through with a small delay. Hmmmm.... not blocked but I wonder what it means to be 'blocked'? How fast should the water take to pass from top to bottom?

Took radiator to friend that does custom radiator work. He flow tested it (fancy way of saying he ran water through it under pressure). Water weent through but --- he said it was blocked. Turns out that water should flow through with almost no resistance. Anything else is considerred blocked.

Recored the radiator with a nice high efficency 3 row, and had a petcock installed ($230 or so for the job at Jerry Young Radiator in LA). He saved the old core so I could see the 'blockage'. The rods were passable, but clearly had a lot of buildup in them. Too bad you cant see this due to the way the filler is set off on an ear.

Replaced and ran (without thermostat). Temp would not reach operating temp. Replaced thermostat with new 160 degree (dont trust old thermostats and I live in a warm climate). Runs perfect.

So the lesson is: Blocked isnt really 'blocked'. If the radiator flows slowly it is blocked. Water should run through with no noticable restriction. AND dont run plain water in your car - most of the junk was clearly calcification and the pitting in the pump and thermostat housing was also from running water without additives. I ended up replacing the thermostat housing as well because of severe pitting.

I run my cars with 1/4 coolant, 3/4 distilled water, and Water Wetter (1/2 pint for an opel).

BTW: I got lucky and dont have any head damage. But I bet the original engine does. Too bad, the internals look as if it was rebuilt last week.

· Member
583 Posts
Sandy beaches.

Hey Mikey!,

Several years ago I purchased a new engine from Nissan to install in a 1978 280Z. Deciding to go all out, I had the radiator recored prior to installing the new engine. Installed engine and all was well for the first couple of days. After that I noticed that the engine was running way hot. This was in 70 degree weather. Not a chance! Even in Texas.

Checked timing, water level, thermostat. Problem persisted. As last resort, I removed the radiator and took it back to the shop that built it. Same test, pressurized flow test. Minimal circulation.

The shop removed the top and bottom tanks. Found the bottom and lower 2/3 of radiator full of fine grained sand. No beach within 500 miles! Evidently, the block had not been thoroughly cleaned at the foundery after casting. The shop guy said that he had six new Ford diesel trucks with the same problem.

Moral of the story, never take anything for granted.

Keep the shiny side up.

· Member
88 Posts
Discussion Starter · #3 ·
And even Studebakers ...

I have a 49 stude that always ran a bit hot but not overheating. It had a good radiator (Jerry Young again), good pump, and a good thermostat. It still always ran a bit hot. So I decide to detail the engine starting with a good wash with detergent and a brush. One of the freeze plugs didnt come very clean, so I reached into the recess to scrape the remaining crud out and found that the crud WAS the plug.

Pulled the plug (and the others) and found that there was no passage - just more cast iron (I thought). I asked an experienced (read crotchety) local guy that only worked on studes and he told me to use a coathanger and water hose to drag all the stuff out of the block. I ended up removing several pounds of dirt. I was amazed that the car could cool at all! I also had to remove and flush the head and then take aother pound of junk out of the fresh radiator.

I suspect that the previous owner was running mud as a coolant.

2,111 Posts
i had a 52 packard flat head straight 8 that had 2 of 9 freezeplugs

the rest were plugged solid gunk, pulled out near 2 ice cream buckets of gunk out of the block, just where i could reach through the freeze plugs and a side plate in the side of the block on the opposite side of the engine. still always ran a little warm until i blew a buncha crap outta muffler, which ended up being DOG FOOD and ACORNS!!! dumping a quart of tranny fluid fallowed by a half gallon water really helped it run better to, freed up some sticky valves and made lotta smoke :D

· 4ZUA787
664 Posts
tranny fluid is a great engine cleaning product ive used it to clean out cylnders befor helps clean the intakes as well. follow with a bunch of this aersol intake cleaner and it will take a lot of crap out.
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