Running hot at highway speeds only. Why......... - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• Running hot at highway speeds only. Why......... by heywier427 on 28 May, 2015 18:14
• So...
  
  81 mk1, 1.6 n/a, saab intercooler, gt15 turbo, large ext. oil cooler. mk2 aluminum radiator, modded td pump, approx. 25lbs max boost. 12mm head, metal 3 hole, arp studs. Also ac and automatic.
  
  Had this problem since I built the car and +/- 80,xxx miles.  Time to find a god damn solution.  I thought upgrading to a full aluminum 2 row radiator would solve it.
  
  From what I've read, most likely culprit is the lower rad hose sucking shut at higher rpms.  That, or the water pump belt is slipping on the pulley at higher rpms.
  
  Car runs great.  It is my daily, and I drive +/- 150 miles a day. 
  
  When pushing it on highway, the temp will start to climb steadily until I back off and let it cool down for a few miles.  Will run at 1/2 mark all day with the ac on at 65 mph and at idle.
  
  I have the 3.12 final drive auto trans, and 75 mph is 3 grand (not really pushing it, I don't feel).  At 75 the temp will rise but slow and steady.  Put it to the floor for 20-30 seconds and it rises pretty quickly to the last 2 bars, and stays there for a while after I slow down. (I can absolutely put it into the red if I keep my foot down).  I have gps'd at 118 down hill
  
  So many threads with no real answers.  Been reading for a year.
  
  Last week upgraded to the ebay mk2 2 row aluminum radiator, also replaced all hoses.  Didn't help. 
  
  So if it is the lower rad hose collapsing, what kind/where can I get the spring to put inside of it?  It has a downward and to the left 90 deg. bend in it.  It is 1.5" in diameter.  I don't see a brand new hose collapsing, especially when its mostly made up of molded elbows.
  
  I don't believe its the water pump pulley slipping on the belt, as I have tried it tight as ***, with the same result.  Water pump is new 30,xxx miles ago.  Metal impeller, pulley is the correct size.  Heater core is new/good.  Heat is good all the time, minutes after start up.
  
  Pump is timed correctly and a bit advanced.
  
  Thermostat has been changed numerous times all tested before installed.  Settled on a 160f with a 175 fan switch.
  
  Egt's are normal 650 @65mph and can push it to 1350 when on full up a hill.  A long hill.  Takes a good bit of abuse to reach 1200.
  
  Its a solid, well built, reliable car.  And this is its only hiccup.
  
  Anyone have any other suggestions... It is not the head gasket.  No gases present in coolant.
  
  Let me know if you need any other info.
  
  Thanks,
  
  Tom.
  
  P.s. this is the only thing holding me back from going holset!!!!!!  Lets figure this out!!!
  
  Also, added a large GM coolant overflow in addition to my stock overflow, in hopes that adding damn near a gallon of extra coolant to the system would help.  Nope...  System has been flushed, back flushed, chem flushed.  The inside of this block is cleaner that my toilet!
  
  
• #1 by theman53 on 28 May, 2015 20:23
• What is your coolant temp?
• #2 by DogDiesel on 29 May, 2015 05:55
• Does your fan come on?
  
  I had this problem in a very minor way before I upgraded to the Two ROW Schrirroco radiator.  I determined I simply did not have enough radiator.   
  I installed a switch and would manually turn on my fan and my temps were normal. 
  I am only running a 1.9 AAZ with Giles pump..  3:67 gears and .71 OD
  
  After I installed  the new radiator, I cannot make it overheat when there are no leaks, correct antifreeze solution, etc.
  
  Because I have AC with Serpentine, I use the Schirroco radiator with the bottom outlet on the left.  I use metal piping on the coolant extension in a custom setup.
  
  I used a cuttoff disk and made my fan shroud fit the radiator, drilled holes for perfect bolt up.  I sealed the edges with rubber pipe before I bolted on shroud, and it pulls hot air quickly and then fan goes off.  Since the Schirroco race radiators have a smaller hole for the sender, I used  a 170 degree sender to fit the hole, customised my wiring and used a small bent rubber hose to serve as my connecter cover for asthetic look and connecter protection.
  
  Radiator size IMHO matters.
  
  Wayne
  
  
• #3 by air-cooled or diesel on 29 May, 2015 06:48
• the trans you have is it stock or have you lowered the ratios?
• #4 by heywier427 on 29 May, 2015 07:56
• What is your coolant temp?
  
  Honestly i have always used the stock gauge.  I know, lazy.  It could be wrong and all of this pointless!   When I IR the top hose at idle, it is always around 180 ish.
  
  Does your fan come on?
  
  Fan absolutly comes on, at temp and with ac.  2 speed mk2 fan wired for higher speed.  Stock fan shroud.  Foam/rubber gaskets used all around.  Bottom is blocked, top is blocked by hood sound deadener.
  
  No leaks in system at all.  Coolant never ever drops.  Could just be not enough radiator...  but unfortunaly nothing else is going to fit.  When building the car, i seached everywhere for a good solution, and could not find one.  Even a custom one isnt much bigger.  Space is limited between the ac compressor, and the intercooler pipe.  The Mk2 aluminum one fits perfectly, and i was hoping it was the cureall.  Before the mk2 rad. I use a 1979 peugot radator that had the same demetions, but a bit smaller.
  
  http://www.ebay.com/itm/ALUMINUM-RADIATOR-VW-GOLF-GTI-JETTA-MK2-Corrado-Scirocco-Coupe-1-8V-86-95-/261763767683?fits=Make%3AVolkswagen&hash=item3cf2561d83&vxp=mtr#ht_5173wt_882
  
  
  the trans you have is it stock or have you lowered the ratios?
  
  stock ratio's.  Trans is coded "TJ" and is the longest geared auto tranny.  Was really watching the rpm's today and 75 mph is +/- 2800.
  
  Ill snap a few pictures tonight.
  
  Also forgot to mention that this is a "my setup" problem, as the last engine went for 50-60,xxx before I bent a rod!  It had an estimate 400xxx when i got it.  Compression was 120, 140,180,240 !!!  It did  not like the winter
  
  It had the same symptoms.
  
  Maybe the stock fan shroud is too restictive at speed?  Rubber flaps are there, althought the lower one can only push open about an inch, due to the ac compressor line being there.
  
  Was also told that the coolant could be circulating so fast, it doesnt have time to cool down passing through the radiator?
  
  Im stumpped!
• #5 by air-cooled or diesel on 29 May, 2015 09:55
• one thing id start with is to squeeze all coolant hoses, feel if any are soft or seem like they may be collapsing, this cannt tell you all, but if you can feel it with your hands,,,a internal spring may help. on one hand im thinking 2800rpm@75mph may be low,,the high gear of trans may be overheating at high speeds esp w/mid revs, with the load, extra heat. had that problem with bugs, you have to use stock 4th ratio as top gear, even if you had a 5th, a few special 5gear trans were available, was esp a problem for air-cooled cars, as in top gear the low gearing added too much load and heated up motor. i still have a trans for t/1 thats junk, cannt get rid of it, prob not for free either, heheh, its a good trans except it wont go above 65-70mph and heats up, next time i ll go to carter gear box and stick with stand 4th gear.
  whats your oil temps at high speed, also heating up? as you say you have a good ext oil cooler, should get a temp reading post cooler.
• #6 by heywier427 on 29 May, 2015 10:47
• Oil temp I believe is post cooler, as it is in the stock location on top of the oil filter housing.  (stock oil cooler is removed/replaced with thermo sandwich cooler).
  
  Temps are normal as far as my knowledge.  Hovers around 85-90c and touches 100c when getting hot. Never seen it past 100.  100c = 212f which is the norm for oil temps.
  
  The coolant hoses are all new.  I can definitely squeeze them and get them to collapse, but they are by no means, soft/mushy/old feeling.
  
  If the trans is geared too low, I would think it would want to heat up during slower/normal driving, not just full throttle/high rpm bursts.  I can lug it up a long hill at 65, having to give it progressive throttle to keep speed, and no heating up.  Possibility though.  Drive in 2nd gear and see if it heats up just as quick?
  
  Would I be able to buy a cheapo elec. temp gauge at autozone and hook it up in series with the stock temp sensor?  Would the output voltage be enough to give both sensors a true reading?
  
  I guess that's the best place to start.  See what the temps are really getting to.  I might just have a vdo temp gauge kicking around.
• #7 by Dakotakid on 29 May, 2015 11:42
• I honestly do not have a lot to ad.
  I did "live" with an '82 n/a Jetta with automatic for over 400,000 miles many years ago.
  
  My trans was clearly stamped "TO" for a code. Not TG or TC. The "O" was clearly fully stamped...and THAT code has never turned up in any of the charts. My final ratio certainly was NOT 3.12.....probably more of the 3.42 or 3.51 (I would have to look at the chart again). At 75 mph, my engine MUST have been doing in excess of 4,000 rpm. I mean, it was insanely high.
  
  Here is the meat of my message: even though I had different gearing (easier to turn) and ran conservatively narrow-ish tires and changed ATF every 5,000 miles and often changed the gear lube as well............that engine always ran warmer than any standard shift VW diesel I have ever owned since or before.
  
  I always contributed that to just how much more power (noticeably) it takes to run that automatic box. I mean, I literally had sciatic problems from driving that beeotch because I CONSTANTLY had my foot mashed to the front bumper! And, my final drive ratio was a whole lot more-forgiving than your 3.12.
  
  If I were you, I would consider: 1) tire size and proper air pressure....(you know....the "housewife " stuff") and 2) performing good maintenance on the trans (ATF changes often).
  
  I think you are pulling harder on that engine than you are seemingly aware of.
  
  Edit: Just for your info: those two throttle cables are no longer available. The one to the pump doesn't last long either. I would start looking for spares like last year already!
• #8 by heywier427 on 29 May, 2015 12:28
• Lol at everything you said
  
  I too drove n/a on my mk2 for 200xxx, with ac!  You better be driving looking 3 cars a head of you, or forget about keeping up with the fast lane!!!  Learning to drive slow makes you fast!
  
  I have 3 spare trannys, all with cables!  the hardest one to find is the one off the pump.  You absolutely can use a 5 speed cable though.  You have to unbolt the pump cable bracket, and move it forward, so it is only held on my 1 bolt.  That's how I have it now, as Im hording the old cable
  
  My wheels tires are an awesome combo!  Mini cooper 15" "7 holes"  They are 11lbs!! with a 175/65/15 tire, inflated to 40lbs. 
  
  I can instantly feel the difference when I put my winter tires on.  They are ridiculously light!
  
  I know its def. time to change the gearbox fluid.  Change the trans fluid every 15k.
  
  Probalby time to add a trans cooler as well.
  
  Thanks for the info.
  
  I am at stock ride height.  Well 3/4" lower.  Have H&R OE sports and Koni oranges.  Great ride.
• #9 by air-cooled or diesel on 29 May, 2015 14:04
• at lower speeds at the same rpm you have a lot less load; so you wont run hot in a lower gear; high gear at above 65mph sounds like either you need to raise the final drive gears, or 4th gear; 4 spd auto right? you (may) need higher rpms at that speed; in other words a higher ratio in 4th. 3.whatever; 3.12? sounds ridiculously low and with a low 4th that effectively lowers od more; in comparison,,. 1 thing that (may) help is to make the water pump turn faster, could help some, but not a very good one, me thinks, more water may help,,some. but a better gearing also will raise rpms, more water flow, some more cooling, there.
  auto trans needs fluid changed at about 60k, so often isnt necessary and sometimes can be counter productive. use correct fluid for a transaxle, i use synthetic, but then again i had flushed it in very early in the couple of autos i have, use good fluid. change out all the fluid(trq conv). replace filter.
  oh yea, id shy away from buying a cheapo sensor or set-up, vdo is definitely good. maybe for this a run-of-the-mill set up is better for you.     
• #10 by theman53 on 29 May, 2015 18:10
• 180 ish is not too hot. Watch it and run it.
• #11 by heywier427 on 24 Jun, 2015 14:05
• Hooray.
  
  I figured it out!
  
  Both the old puegot radiator and the new aluminum radiator did not have a blocker baffle imbetween the top and bottom radiator inlet/outlet.
  
  WTF!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
  
  So the fluid was not being forced through the radiator tubes, rather taking the path of least resistance, and just going up and out!
  
  Just emailed Giles about building me a super pump!
  
  I am so relieved this is over, and relatively simple to fix!
  
  Now I have to spend 2 more K on a pump/turbo/downpipe!
  
  he2221 here I come!
  
  YAY!!!!!
  
  Thanks for everyone's input.
• #12 by mtrans on 25 Jun, 2015 12:43
• Do you open radiator and find that?
• #13 by heywier427 on 25 Jun, 2015 13:24
• Kinda.
  
  I removed the radiator and shinned a flashlight in the upper hole and it was really really bright at the bottom hole. If there was a baffle there, it should have blocked most of the light.
  
  I then got a long metal zip tie, and it passed right down and through without hitting anything.
  
  Then I got really nerdy and used my inspection scope. No blocker to be seen.
  
  I cut an 1/8th inch section in between the upper and lower outlets, then made a blocker plate out of 1/8" flat stock I had.
  
  Welded it back up, and reassembled. 
  
  I can now drive foot down with the ac on, till my egt's prevent me from going faster.
  
  My Ebay GT15 is on the way out, and my egt's are rising faster due to the loss of airflow.
  
  From a dead stop at an entrance ramp,  I can floor it and reach 100 mph at around 1200 degs f.  A/C on.
  
  With the 160 Deg. thermostat, the temp needle does not go past 1 line past half way ever.
  
  Very happy camper.
  
  
• #14 by smutts on 01 Jul, 2015 15:21
• Well spotted  that is a good save, I now try to never, ever, underestimate other peoples or manufacturers ability to bollocks things up.